1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright (c) 2019, Joyent, Inc.
24 * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 * Copyright 2017 Nexenta Systems, Inc. All rights reserved.
27 * Copyright (c) 2011, 2019, Delphix. All rights reserved.
28 * Copyright (c) 2020, George Amanakis. All rights reserved.
29 * Copyright (c) 2020, The FreeBSD Foundation [1]
30 *
31 * [1] Portions of this software were developed by Allan Jude
32 * under sponsorship from the FreeBSD Foundation.
33 */
34
35 /*
36 * DVA-based Adjustable Replacement Cache
37 *
38 * While much of the theory of operation used here is
39 * based on the self-tuning, low overhead replacement cache
40 * presented by Megiddo and Modha at FAST 2003, there are some
41 * significant differences:
42 *
43 * 1. The Megiddo and Modha model assumes any page is evictable.
44 * Pages in its cache cannot be "locked" into memory. This makes
45 * the eviction algorithm simple: evict the last page in the list.
46 * This also make the performance characteristics easy to reason
47 * about. Our cache is not so simple. At any given moment, some
48 * subset of the blocks in the cache are un-evictable because we
49 * have handed out a reference to them. Blocks are only evictable
50 * when there are no external references active. This makes
51 * eviction far more problematic: we choose to evict the evictable
52 * blocks that are the "lowest" in the list.
53 *
54 * There are times when it is not possible to evict the requested
55 * space. In these circumstances we are unable to adjust the cache
56 * size. To prevent the cache growing unbounded at these times we
57 * implement a "cache throttle" that slows the flow of new data
58 * into the cache until we can make space available.
59 *
60 * 2. The Megiddo and Modha model assumes a fixed cache size.
61 * Pages are evicted when the cache is full and there is a cache
62 * miss. Our model has a variable sized cache. It grows with
63 * high use, but also tries to react to memory pressure from the
64 * operating system: decreasing its size when system memory is
65 * tight.
66 *
67 * 3. The Megiddo and Modha model assumes a fixed page size. All
68 * elements of the cache are therefore exactly the same size. So
69 * when adjusting the cache size following a cache miss, its simply
70 * a matter of choosing a single page to evict. In our model, we
71 * have variable sized cache blocks (rangeing from 512 bytes to
72 * 128K bytes). We therefore choose a set of blocks to evict to make
73 * space for a cache miss that approximates as closely as possible
74 * the space used by the new block.
75 *
76 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
77 * by N. Megiddo & D. Modha, FAST 2003
78 */
79
80 /*
81 * The locking model:
82 *
83 * A new reference to a cache buffer can be obtained in two
84 * ways: 1) via a hash table lookup using the DVA as a key,
85 * or 2) via one of the ARC lists. The arc_read() interface
86 * uses method 1, while the internal ARC algorithms for
87 * adjusting the cache use method 2. We therefore provide two
88 * types of locks: 1) the hash table lock array, and 2) the
89 * ARC list locks.
90 *
91 * Buffers do not have their own mutexes, rather they rely on the
92 * hash table mutexes for the bulk of their protection (i.e. most
93 * fields in the arc_buf_hdr_t are protected by these mutexes).
94 *
95 * buf_hash_find() returns the appropriate mutex (held) when it
96 * locates the requested buffer in the hash table. It returns
97 * NULL for the mutex if the buffer was not in the table.
98 *
99 * buf_hash_remove() expects the appropriate hash mutex to be
100 * already held before it is invoked.
101 *
102 * Each ARC state also has a mutex which is used to protect the
103 * buffer list associated with the state. When attempting to
104 * obtain a hash table lock while holding an ARC list lock you
105 * must use: mutex_tryenter() to avoid deadlock. Also note that
106 * the active state mutex must be held before the ghost state mutex.
107 *
108 * Note that the majority of the performance stats are manipulated
109 * with atomic operations.
110 *
111 * The L2ARC uses the l2ad_mtx on each vdev for the following:
112 *
113 * - L2ARC buflist creation
114 * - L2ARC buflist eviction
115 * - L2ARC write completion, which walks L2ARC buflists
116 * - ARC header destruction, as it removes from L2ARC buflists
117 * - ARC header release, as it removes from L2ARC buflists
118 */
119
120 /*
121 * ARC operation:
122 *
123 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
124 * This structure can point either to a block that is still in the cache or to
125 * one that is only accessible in an L2 ARC device, or it can provide
126 * information about a block that was recently evicted. If a block is
127 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
128 * information to retrieve it from the L2ARC device. This information is
129 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
130 * that is in this state cannot access the data directly.
131 *
132 * Blocks that are actively being referenced or have not been evicted
133 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
134 * the arc_buf_hdr_t that will point to the data block in memory. A block can
135 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
136 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
137 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd).
138 *
139 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the
140 * ability to store the physical data (b_pabd) associated with the DVA of the
141 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block,
142 * it will match its on-disk compression characteristics. This behavior can be
143 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
144 * compressed ARC functionality is disabled, the b_pabd will point to an
145 * uncompressed version of the on-disk data.
146 *
147 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each
148 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
149 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
150 * consumer. The ARC will provide references to this data and will keep it
151 * cached until it is no longer in use. The ARC caches only the L1ARC's physical
152 * data block and will evict any arc_buf_t that is no longer referenced. The
153 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
154 * "overhead_size" kstat.
155 *
156 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or
157 * compressed form. The typical case is that consumers will want uncompressed
158 * data, and when that happens a new data buffer is allocated where the data is
159 * decompressed for them to use. Currently the only consumer who wants
160 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it
161 * exists on disk. When this happens, the arc_buf_t's data buffer is shared
162 * with the arc_buf_hdr_t.
163 *
164 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
165 * first one is owned by a compressed send consumer (and therefore references
166 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be
167 * used by any other consumer (and has its own uncompressed copy of the data
168 * buffer).
169 *
170 * arc_buf_hdr_t
171 * +-----------+
172 * | fields |
173 * | common to |
174 * | L1- and |
175 * | L2ARC |
176 * +-----------+
177 * | l2arc_buf_hdr_t
178 * | |
179 * +-----------+
180 * | l1arc_buf_hdr_t
181 * | | arc_buf_t
182 * | b_buf +------------>+-----------+ arc_buf_t
183 * | b_pabd +-+ |b_next +---->+-----------+
184 * +-----------+ | |-----------| |b_next +-->NULL
185 * | |b_comp = T | +-----------+
186 * | |b_data +-+ |b_comp = F |
187 * | +-----------+ | |b_data +-+
188 * +->+------+ | +-----------+ |
189 * compressed | | | |
190 * data | |<--------------+ | uncompressed
191 * +------+ compressed, | data
192 * shared +-->+------+
193 * data | |
194 * | |
195 * +------+
196 *
197 * When a consumer reads a block, the ARC must first look to see if the
198 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
199 * arc_buf_t and either copies uncompressed data into a new data buffer from an
200 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a
201 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the
202 * hdr is compressed and the desired compression characteristics of the
203 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
204 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
205 * the last buffer in the hdr's b_buf list, however a shared compressed buf can
206 * be anywhere in the hdr's list.
207 *
208 * The diagram below shows an example of an uncompressed ARC hdr that is
209 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is
210 * the last element in the buf list):
211 *
212 * arc_buf_hdr_t
213 * +-----------+
214 * | |
215 * | |
216 * | |
217 * +-----------+
218 * l2arc_buf_hdr_t| |
219 * | |
220 * +-----------+
221 * l1arc_buf_hdr_t| |
222 * | | arc_buf_t (shared)
223 * | b_buf +------------>+---------+ arc_buf_t
224 * | | |b_next +---->+---------+
225 * | b_pabd +-+ |---------| |b_next +-->NULL
226 * +-----------+ | | | +---------+
227 * | |b_data +-+ | |
228 * | +---------+ | |b_data +-+
229 * +->+------+ | +---------+ |
230 * | | | |
231 * uncompressed | | | |
232 * data +------+ | |
233 * ^ +->+------+ |
234 * | uncompressed | | |
235 * | data | | |
236 * | +------+ |
237 * +---------------------------------+
238 *
239 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd
240 * since the physical block is about to be rewritten. The new data contents
241 * will be contained in the arc_buf_t. As the I/O pipeline performs the write,
242 * it may compress the data before writing it to disk. The ARC will be called
243 * with the transformed data and will bcopy the transformed on-disk block into
244 * a newly allocated b_pabd. Writes are always done into buffers which have
245 * either been loaned (and hence are new and don't have other readers) or
246 * buffers which have been released (and hence have their own hdr, if there
247 * were originally other readers of the buf's original hdr). This ensures that
248 * the ARC only needs to update a single buf and its hdr after a write occurs.
249 *
250 * When the L2ARC is in use, it will also take advantage of the b_pabd. The
251 * L2ARC will always write the contents of b_pabd to the L2ARC. This means
252 * that when compressed ARC is enabled that the L2ARC blocks are identical
253 * to the on-disk block in the main data pool. This provides a significant
254 * advantage since the ARC can leverage the bp's checksum when reading from the
255 * L2ARC to determine if the contents are valid. However, if the compressed
256 * ARC is disabled, then the L2ARC's block must be transformed to look
257 * like the physical block in the main data pool before comparing the
258 * checksum and determining its validity.
259 *
260 * The L1ARC has a slightly different system for storing encrypted data.
261 * Raw (encrypted + possibly compressed) data has a few subtle differences from
262 * data that is just compressed. The biggest difference is that it is not
263 * possible to decrypt encrypted data (or visa versa) if the keys aren't loaded.
264 * The other difference is that encryption cannot be treated as a suggestion.
265 * If a caller would prefer compressed data, but they actually wind up with
266 * uncompressed data the worst thing that could happen is there might be a
267 * performance hit. If the caller requests encrypted data, however, we must be
268 * sure they actually get it or else secret information could be leaked. Raw
269 * data is stored in hdr->b_crypt_hdr.b_rabd. An encrypted header, therefore,
270 * may have both an encrypted version and a decrypted version of its data at
271 * once. When a caller needs a raw arc_buf_t, it is allocated and the data is
272 * copied out of this header. To avoid complications with b_pabd, raw buffers
273 * cannot be shared.
274 */
275
276 #include <sys/spa.h>
277 #include <sys/zio.h>
278 #include <sys/spa_impl.h>
279 #include <sys/zio_compress.h>
280 #include <sys/zio_checksum.h>
281 #include <sys/zfs_context.h>
282 #include <sys/arc.h>
283 #include <sys/refcount.h>
284 #include <sys/vdev.h>
285 #include <sys/vdev_impl.h>
286 #include <sys/dsl_pool.h>
287 #include <sys/zfs_zone.h>
288 #include <sys/zio_checksum.h>
289 #include <sys/multilist.h>
290 #include <sys/abd.h>
291 #include <sys/zil.h>
292 #include <sys/fm/fs/zfs.h>
293 #ifdef _KERNEL
294 #include <sys/vmsystm.h>
295 #include <vm/anon.h>
296 #include <sys/fs/swapnode.h>
297 #include <sys/dnlc.h>
298 #endif
299 #include <sys/callb.h>
300 #include <sys/kstat.h>
301 #include <sys/zthr.h>
302 #include <zfs_fletcher.h>
303 #include <sys/arc_impl.h>
304 #include <sys/aggsum.h>
305 #include <sys/cityhash.h>
306 #include <sys/param.h>
307
308 #ifndef _KERNEL
309 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
310 boolean_t arc_watch = B_FALSE;
311 int arc_procfd;
312 #endif
313
314 /*
315 * This thread's job is to keep enough free memory in the system, by
316 * calling arc_kmem_reap_now() plus arc_shrink(), which improves
317 * arc_available_memory().
318 */
319 static zthr_t *arc_reap_zthr;
320
321 /*
322 * This thread's job is to keep arc_size under arc_c, by calling
323 * arc_adjust(), which improves arc_is_overflowing().
324 */
325 static zthr_t *arc_adjust_zthr;
326
327 static kmutex_t arc_adjust_lock;
328 static kcondvar_t arc_adjust_waiters_cv;
329 static boolean_t arc_adjust_needed = B_FALSE;
330
331 uint_t arc_reduce_dnlc_percent = 3;
332
333 /*
334 * The number of headers to evict in arc_evict_state_impl() before
335 * dropping the sublist lock and evicting from another sublist. A lower
336 * value means we're more likely to evict the "correct" header (i.e. the
337 * oldest header in the arc state), but comes with higher overhead
338 * (i.e. more invocations of arc_evict_state_impl()).
339 */
340 int zfs_arc_evict_batch_limit = 10;
341
342 /* number of seconds before growing cache again */
343 int arc_grow_retry = 60;
344
345 /*
346 * Minimum time between calls to arc_kmem_reap_soon(). Note that this will
347 * be converted to ticks, so with the default hz=100, a setting of 15 ms
348 * will actually wait 2 ticks, or 20ms.
349 */
350 int arc_kmem_cache_reap_retry_ms = 1000;
351
352 /* shift of arc_c for calculating overflow limit in arc_get_data_impl */
353 int zfs_arc_overflow_shift = 3;
354
355 /* shift of arc_c for calculating both min and max arc_p */
356 int arc_p_min_shift = 4;
357
358 /* log2(fraction of arc to reclaim) */
359 int arc_shrink_shift = 7;
360
361 /*
362 * log2(fraction of ARC which must be free to allow growing).
363 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
364 * when reading a new block into the ARC, we will evict an equal-sized block
365 * from the ARC.
366 *
367 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
368 * we will still not allow it to grow.
369 */
370 int arc_no_grow_shift = 5;
371
372
373 /*
374 * minimum lifespan of a prefetch block in clock ticks
375 * (initialized in arc_init())
376 */
377 static int zfs_arc_min_prefetch_ms = 1;
378 static int zfs_arc_min_prescient_prefetch_ms = 6;
379
380 /*
381 * If this percent of memory is free, don't throttle.
382 */
383 int arc_lotsfree_percent = 10;
384
385 static boolean_t arc_initialized;
386
387 /*
388 * The arc has filled available memory and has now warmed up.
389 */
390 static boolean_t arc_warm;
391
392 /*
393 * log2 fraction of the zio arena to keep free.
394 */
395 int arc_zio_arena_free_shift = 2;
396
397 /*
398 * These tunables are for performance analysis.
399 */
400 uint64_t zfs_arc_max;
401 uint64_t zfs_arc_min;
402 uint64_t zfs_arc_meta_limit = 0;
403 uint64_t zfs_arc_meta_min = 0;
404 int zfs_arc_grow_retry = 0;
405 int zfs_arc_shrink_shift = 0;
406 int zfs_arc_p_min_shift = 0;
407 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
408
409 /*
410 * ARC dirty data constraints for arc_tempreserve_space() throttle
411 */
412 uint_t zfs_arc_dirty_limit_percent = 50; /* total dirty data limit */
413 uint_t zfs_arc_anon_limit_percent = 25; /* anon block dirty limit */
414 uint_t zfs_arc_pool_dirty_percent = 20; /* each pool's anon allowance */
415
416 boolean_t zfs_compressed_arc_enabled = B_TRUE;
417
418 /* The 6 states: */
419 static arc_state_t ARC_anon;
420 static arc_state_t ARC_mru;
421 static arc_state_t ARC_mru_ghost;
422 static arc_state_t ARC_mfu;
423 static arc_state_t ARC_mfu_ghost;
424 static arc_state_t ARC_l2c_only;
425
426 arc_stats_t arc_stats = {
427 { "hits", KSTAT_DATA_UINT64 },
428 { "misses", KSTAT_DATA_UINT64 },
429 { "demand_data_hits", KSTAT_DATA_UINT64 },
430 { "demand_data_misses", KSTAT_DATA_UINT64 },
431 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
432 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
433 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
434 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
435 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
436 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
437 { "mru_hits", KSTAT_DATA_UINT64 },
438 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
439 { "mfu_hits", KSTAT_DATA_UINT64 },
440 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
441 { "deleted", KSTAT_DATA_UINT64 },
442 { "mutex_miss", KSTAT_DATA_UINT64 },
443 { "access_skip", KSTAT_DATA_UINT64 },
444 { "evict_skip", KSTAT_DATA_UINT64 },
445 { "evict_not_enough", KSTAT_DATA_UINT64 },
446 { "evict_l2_cached", KSTAT_DATA_UINT64 },
447 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
448 { "evict_l2_eligible_mfu", KSTAT_DATA_UINT64 },
449 { "evict_l2_eligible_mru", KSTAT_DATA_UINT64 },
450 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
451 { "evict_l2_skip", KSTAT_DATA_UINT64 },
452 { "hash_elements", KSTAT_DATA_UINT64 },
453 { "hash_elements_max", KSTAT_DATA_UINT64 },
454 { "hash_collisions", KSTAT_DATA_UINT64 },
455 { "hash_chains", KSTAT_DATA_UINT64 },
456 { "hash_chain_max", KSTAT_DATA_UINT64 },
457 { "p", KSTAT_DATA_UINT64 },
458 { "c", KSTAT_DATA_UINT64 },
459 { "c_min", KSTAT_DATA_UINT64 },
460 { "c_max", KSTAT_DATA_UINT64 },
461 { "size", KSTAT_DATA_UINT64 },
462 { "compressed_size", KSTAT_DATA_UINT64 },
463 { "uncompressed_size", KSTAT_DATA_UINT64 },
464 { "overhead_size", KSTAT_DATA_UINT64 },
465 { "hdr_size", KSTAT_DATA_UINT64 },
466 { "data_size", KSTAT_DATA_UINT64 },
467 { "metadata_size", KSTAT_DATA_UINT64 },
468 { "other_size", KSTAT_DATA_UINT64 },
469 { "anon_size", KSTAT_DATA_UINT64 },
470 { "anon_evictable_data", KSTAT_DATA_UINT64 },
471 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
472 { "mru_size", KSTAT_DATA_UINT64 },
473 { "mru_evictable_data", KSTAT_DATA_UINT64 },
474 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
475 { "mru_ghost_size", KSTAT_DATA_UINT64 },
476 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
477 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
478 { "mfu_size", KSTAT_DATA_UINT64 },
479 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
480 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
481 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
482 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
483 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
484 { "l2_hits", KSTAT_DATA_UINT64 },
485 { "l2_misses", KSTAT_DATA_UINT64 },
486 { "l2_prefetch_asize", KSTAT_DATA_UINT64 },
487 { "l2_mru_asize", KSTAT_DATA_UINT64 },
488 { "l2_mfu_asize", KSTAT_DATA_UINT64 },
489 { "l2_bufc_data_asize", KSTAT_DATA_UINT64 },
490 { "l2_bufc_metadata_asize", KSTAT_DATA_UINT64 },
491 { "l2_feeds", KSTAT_DATA_UINT64 },
492 { "l2_rw_clash", KSTAT_DATA_UINT64 },
493 { "l2_read_bytes", KSTAT_DATA_UINT64 },
494 { "l2_write_bytes", KSTAT_DATA_UINT64 },
495 { "l2_writes_sent", KSTAT_DATA_UINT64 },
496 { "l2_writes_done", KSTAT_DATA_UINT64 },
497 { "l2_writes_error", KSTAT_DATA_UINT64 },
498 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
499 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
500 { "l2_evict_reading", KSTAT_DATA_UINT64 },
501 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
502 { "l2_free_on_write", KSTAT_DATA_UINT64 },
503 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
504 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
505 { "l2_io_error", KSTAT_DATA_UINT64 },
506 { "l2_size", KSTAT_DATA_UINT64 },
507 { "l2_asize", KSTAT_DATA_UINT64 },
508 { "l2_hdr_size", KSTAT_DATA_UINT64 },
509 { "l2_log_blk_writes", KSTAT_DATA_UINT64 },
510 { "l2_log_blk_avg_asize", KSTAT_DATA_UINT64 },
511 { "l2_log_blk_asize", KSTAT_DATA_UINT64 },
512 { "l2_log_blk_count", KSTAT_DATA_UINT64 },
513 { "l2_data_to_meta_ratio", KSTAT_DATA_UINT64 },
514 { "l2_rebuild_success", KSTAT_DATA_UINT64 },
515 { "l2_rebuild_unsupported", KSTAT_DATA_UINT64 },
516 { "l2_rebuild_io_errors", KSTAT_DATA_UINT64 },
517 { "l2_rebuild_dh_errors", KSTAT_DATA_UINT64 },
518 { "l2_rebuild_cksum_lb_errors", KSTAT_DATA_UINT64 },
519 { "l2_rebuild_lowmem", KSTAT_DATA_UINT64 },
520 { "l2_rebuild_size", KSTAT_DATA_UINT64 },
521 { "l2_rebuild_asize", KSTAT_DATA_UINT64 },
522 { "l2_rebuild_bufs", KSTAT_DATA_UINT64 },
523 { "l2_rebuild_bufs_precached", KSTAT_DATA_UINT64 },
524 { "l2_rebuild_log_blks", KSTAT_DATA_UINT64 },
525 { "memory_throttle_count", KSTAT_DATA_UINT64 },
526 { "arc_meta_used", KSTAT_DATA_UINT64 },
527 { "arc_meta_limit", KSTAT_DATA_UINT64 },
528 { "arc_meta_max", KSTAT_DATA_UINT64 },
529 { "arc_meta_min", KSTAT_DATA_UINT64 },
530 { "async_upgrade_sync", KSTAT_DATA_UINT64 },
531 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
532 { "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 },
533 };
534
535 #define ARCSTAT_MAX(stat, val) { \
536 uint64_t m; \
537 while ((val) > (m = arc_stats.stat.value.ui64) && \
538 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
539 continue; \
540 }
541
542 #define ARCSTAT_MAXSTAT(stat) \
543 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
544
545 /*
546 * We define a macro to allow ARC hits/misses to be easily broken down by
547 * two separate conditions, giving a total of four different subtypes for
548 * each of hits and misses (so eight statistics total).
549 */
550 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
551 if (cond1) { \
552 if (cond2) { \
553 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
554 } else { \
555 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
556 } \
557 } else { \
558 if (cond2) { \
559 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
560 } else { \
561 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
562 } \
563 }
564
565 /*
566 * This macro allows us to use kstats as floating averages. Each time we
567 * update this kstat, we first factor it and the update value by
568 * ARCSTAT_AVG_FACTOR to shrink the new value's contribution to the overall
569 * average. This macro assumes that integer loads and stores are atomic, but
570 * is not safe for multiple writers updating the kstat in parallel (only the
571 * last writer's update will remain).
572 */
573 #define ARCSTAT_F_AVG_FACTOR 3
574 #define ARCSTAT_F_AVG(stat, value) \
575 do { \
576 uint64_t x = ARCSTAT(stat); \
577 x = x - x / ARCSTAT_F_AVG_FACTOR + \
578 (value) / ARCSTAT_F_AVG_FACTOR; \
579 ARCSTAT(stat) = x; \
580 _NOTE(CONSTCOND) \
581 } while (0)
582
583 kstat_t *arc_ksp;
584 static arc_state_t *arc_anon;
585 static arc_state_t *arc_mru;
586 static arc_state_t *arc_mru_ghost;
587 static arc_state_t *arc_mfu;
588 static arc_state_t *arc_mfu_ghost;
589 static arc_state_t *arc_l2c_only;
590
591 /*
592 * There are also some ARC variables that we want to export, but that are
593 * updated so often that having the canonical representation be the statistic
594 * variable causes a performance bottleneck. We want to use aggsum_t's for these
595 * instead, but still be able to export the kstat in the same way as before.
596 * The solution is to always use the aggsum version, except in the kstat update
597 * callback.
598 */
599 aggsum_t arc_size;
600 aggsum_t arc_meta_used;
601 aggsum_t astat_data_size;
602 aggsum_t astat_metadata_size;
603 aggsum_t astat_hdr_size;
604 aggsum_t astat_other_size;
605 aggsum_t astat_l2_hdr_size;
606
607 static int arc_no_grow; /* Don't try to grow cache size */
608 static hrtime_t arc_growtime;
609 static uint64_t arc_tempreserve;
610 static uint64_t arc_loaned_bytes;
611
612 #define GHOST_STATE(state) \
613 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
614 (state) == arc_l2c_only)
615
616 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
617 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
618 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
619 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
620 #define HDR_PRESCIENT_PREFETCH(hdr) \
621 ((hdr)->b_flags & ARC_FLAG_PRESCIENT_PREFETCH)
622 #define HDR_COMPRESSION_ENABLED(hdr) \
623 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
624
625 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
626 #define HDR_L2_READING(hdr) \
627 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
628 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
629 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
630 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
631 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
632 #define HDR_PROTECTED(hdr) ((hdr)->b_flags & ARC_FLAG_PROTECTED)
633 #define HDR_NOAUTH(hdr) ((hdr)->b_flags & ARC_FLAG_NOAUTH)
634 #define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
635
636 #define HDR_ISTYPE_METADATA(hdr) \
637 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
638 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
639
640 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
641 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
642 #define HDR_HAS_RABD(hdr) \
643 (HDR_HAS_L1HDR(hdr) && HDR_PROTECTED(hdr) && \
644 (hdr)->b_crypt_hdr.b_rabd != NULL)
645 #define HDR_ENCRYPTED(hdr) \
646 (HDR_PROTECTED(hdr) && DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot))
647 #define HDR_AUTHENTICATED(hdr) \
648 (HDR_PROTECTED(hdr) && !DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot))
649
650 /* For storing compression mode in b_flags */
651 #define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
652
653 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
654 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
655 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
656 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
657
658 #define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
659 #define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
660 #define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
661 #define ARC_BUF_ENCRYPTED(buf) ((buf)->b_flags & ARC_BUF_FLAG_ENCRYPTED)
662
663 /*
664 * Other sizes
665 */
666
667 #define HDR_FULL_CRYPT_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
668 #define HDR_FULL_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_crypt_hdr))
669 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
670
671 /*
672 * Hash table routines
673 */
674
675 #define HT_LOCK_PAD 64
676
677 struct ht_lock {
678 kmutex_t ht_lock;
679 #ifdef _KERNEL
680 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
681 #endif
682 };
683
684 #define BUF_LOCKS 256
685 typedef struct buf_hash_table {
686 uint64_t ht_mask;
687 arc_buf_hdr_t **ht_table;
688 struct ht_lock ht_locks[BUF_LOCKS];
689 } buf_hash_table_t;
690
691 static buf_hash_table_t buf_hash_table;
692
693 #define BUF_HASH_INDEX(spa, dva, birth) \
694 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
695 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
696 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
697 #define HDR_LOCK(hdr) \
698 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
699
700 uint64_t zfs_crc64_table[256];
701
702 /*
703 * Level 2 ARC
704 */
705
706 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
707 #define L2ARC_HEADROOM 2 /* num of writes */
708 /*
709 * If we discover during ARC scan any buffers to be compressed, we boost
710 * our headroom for the next scanning cycle by this percentage multiple.
711 */
712 #define L2ARC_HEADROOM_BOOST 200
713 #define L2ARC_FEED_SECS 1 /* caching interval secs */
714 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
715
716 /*
717 * We can feed L2ARC from two states of ARC buffers, mru and mfu,
718 * and each of the state has two types: data and metadata.
719 */
720 #define L2ARC_FEED_TYPES 4
721
722
723 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
724 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
725
726 /* L2ARC Performance Tunables */
727 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
728 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
729 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
730 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
731 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
732 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
733 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
734 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
735 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
736 int l2arc_meta_percent = 33; /* limit on headers size */
737
738 /*
739 * L2ARC Internals
740 */
741 static list_t L2ARC_dev_list; /* device list */
742 static list_t *l2arc_dev_list; /* device list pointer */
743 static kmutex_t l2arc_dev_mtx; /* device list mutex */
744 static l2arc_dev_t *l2arc_dev_last; /* last device used */
745 static list_t L2ARC_free_on_write; /* free after write buf list */
746 static list_t *l2arc_free_on_write; /* free after write list ptr */
747 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
748 static uint64_t l2arc_ndev; /* number of devices */
749
750 typedef struct l2arc_read_callback {
751 arc_buf_hdr_t *l2rcb_hdr; /* read header */
752 blkptr_t l2rcb_bp; /* original blkptr */
753 zbookmark_phys_t l2rcb_zb; /* original bookmark */
754 int l2rcb_flags; /* original flags */
755 abd_t *l2rcb_abd; /* temporary buffer */
756 } l2arc_read_callback_t;
757
758 typedef struct l2arc_data_free {
759 /* protected by l2arc_free_on_write_mtx */
760 abd_t *l2df_abd;
761 size_t l2df_size;
762 arc_buf_contents_t l2df_type;
763 list_node_t l2df_list_node;
764 } l2arc_data_free_t;
765
766 static kmutex_t l2arc_feed_thr_lock;
767 static kcondvar_t l2arc_feed_thr_cv;
768 static uint8_t l2arc_thread_exit;
769
770 static kmutex_t l2arc_rebuild_thr_lock;
771 static kcondvar_t l2arc_rebuild_thr_cv;
772
773 enum arc_hdr_alloc_flags {
774 ARC_HDR_ALLOC_RDATA = 0x1,
775 ARC_HDR_DO_ADAPT = 0x2,
776 };
777
778
779 static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *, boolean_t);
780 typedef enum arc_fill_flags {
781 ARC_FILL_LOCKED = 1 << 0, /* hdr lock is held */
782 ARC_FILL_COMPRESSED = 1 << 1, /* fill with compressed data */
783 ARC_FILL_ENCRYPTED = 1 << 2, /* fill with encrypted data */
784 ARC_FILL_NOAUTH = 1 << 3, /* don't attempt to authenticate */
785 ARC_FILL_IN_PLACE = 1 << 4 /* fill in place (special case) */
786 } arc_fill_flags_t;
787
788 static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
789 static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *, boolean_t);
790 static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *);
791 static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
792 static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag);
793 static void arc_hdr_free_pabd(arc_buf_hdr_t *, boolean_t);
794 static void arc_hdr_alloc_pabd(arc_buf_hdr_t *, int);
795 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
796 static boolean_t arc_is_overflowing();
797 static void arc_buf_watch(arc_buf_t *);
798 static l2arc_dev_t *l2arc_vdev_get(vdev_t *vd);
799
800 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
801 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
802 static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
803 static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
804
805 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
806 static void l2arc_read_done(zio_t *);
807 static void l2arc_do_free_on_write(void);
808 static void l2arc_hdr_arcstats_update(arc_buf_hdr_t *hdr, boolean_t incr,
809 boolean_t state_only);
810
811 #define l2arc_hdr_arcstats_increment(hdr) \
812 l2arc_hdr_arcstats_update((hdr), B_TRUE, B_FALSE)
813 #define l2arc_hdr_arcstats_decrement(hdr) \
814 l2arc_hdr_arcstats_update((hdr), B_FALSE, B_FALSE)
815 #define l2arc_hdr_arcstats_increment_state(hdr) \
816 l2arc_hdr_arcstats_update((hdr), B_TRUE, B_TRUE)
817 #define l2arc_hdr_arcstats_decrement_state(hdr) \
818 l2arc_hdr_arcstats_update((hdr), B_FALSE, B_TRUE)
819
820 /*
821 * The arc_all_memory function is a ZoL enhancement that lives in their OSL
822 * code. In user-space code, which is used primarily for testing, we return
823 * half of all memory.
824 */
825 uint64_t
826 arc_all_memory(void)
827 {
828 #ifdef _KERNEL
829 return (ptob(physmem));
830 #else
831 return ((sysconf(_SC_PAGESIZE) * sysconf(_SC_PHYS_PAGES)) / 2);
832 #endif
833 }
834
835 /*
836 * We use Cityhash for this. It's fast, and has good hash properties without
837 * requiring any large static buffers.
838 */
839 static uint64_t
840 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
841 {
842 return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth));
843 }
844
845 #define HDR_EMPTY(hdr) \
846 ((hdr)->b_dva.dva_word[0] == 0 && \
847 (hdr)->b_dva.dva_word[1] == 0)
848
849 #define HDR_EMPTY_OR_LOCKED(hdr) \
850 (HDR_EMPTY(hdr) || MUTEX_HELD(HDR_LOCK(hdr)))
851
852 #define HDR_EQUAL(spa, dva, birth, hdr) \
853 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
854 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
855 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
856
857 static void
858 buf_discard_identity(arc_buf_hdr_t *hdr)
859 {
860 hdr->b_dva.dva_word[0] = 0;
861 hdr->b_dva.dva_word[1] = 0;
862 hdr->b_birth = 0;
863 }
864
865 static arc_buf_hdr_t *
866 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
867 {
868 const dva_t *dva = BP_IDENTITY(bp);
869 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
870 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
871 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
872 arc_buf_hdr_t *hdr;
873
874 mutex_enter(hash_lock);
875 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
876 hdr = hdr->b_hash_next) {
877 if (HDR_EQUAL(spa, dva, birth, hdr)) {
878 *lockp = hash_lock;
879 return (hdr);
880 }
881 }
882 mutex_exit(hash_lock);
883 *lockp = NULL;
884 return (NULL);
885 }
886
887 /*
888 * Insert an entry into the hash table. If there is already an element
889 * equal to elem in the hash table, then the already existing element
890 * will be returned and the new element will not be inserted.
891 * Otherwise returns NULL.
892 * If lockp == NULL, the caller is assumed to already hold the hash lock.
893 */
894 static arc_buf_hdr_t *
895 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
896 {
897 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
898 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
899 arc_buf_hdr_t *fhdr;
900 uint32_t i;
901
902 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
903 ASSERT(hdr->b_birth != 0);
904 ASSERT(!HDR_IN_HASH_TABLE(hdr));
905
906 if (lockp != NULL) {
907 *lockp = hash_lock;
908 mutex_enter(hash_lock);
909 } else {
910 ASSERT(MUTEX_HELD(hash_lock));
911 }
912
913 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
914 fhdr = fhdr->b_hash_next, i++) {
915 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
916 return (fhdr);
917 }
918
919 hdr->b_hash_next = buf_hash_table.ht_table[idx];
920 buf_hash_table.ht_table[idx] = hdr;
921 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
922
923 /* collect some hash table performance data */
924 if (i > 0) {
925 ARCSTAT_BUMP(arcstat_hash_collisions);
926 if (i == 1)
927 ARCSTAT_BUMP(arcstat_hash_chains);
928
929 ARCSTAT_MAX(arcstat_hash_chain_max, i);
930 }
931
932 ARCSTAT_BUMP(arcstat_hash_elements);
933 ARCSTAT_MAXSTAT(arcstat_hash_elements);
934
935 return (NULL);
936 }
937
938 static void
939 buf_hash_remove(arc_buf_hdr_t *hdr)
940 {
941 arc_buf_hdr_t *fhdr, **hdrp;
942 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
943
944 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
945 ASSERT(HDR_IN_HASH_TABLE(hdr));
946
947 hdrp = &buf_hash_table.ht_table[idx];
948 while ((fhdr = *hdrp) != hdr) {
949 ASSERT3P(fhdr, !=, NULL);
950 hdrp = &fhdr->b_hash_next;
951 }
952 *hdrp = hdr->b_hash_next;
953 hdr->b_hash_next = NULL;
954 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
955
956 /* collect some hash table performance data */
957 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
958
959 if (buf_hash_table.ht_table[idx] &&
960 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
961 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
962 }
963
964 /*
965 * l2arc_mfuonly : A ZFS module parameter that controls whether only MFU
966 * metadata and data are cached from ARC into L2ARC.
967 */
968 int l2arc_mfuonly = 0;
969
970 /*
971 * Global data structures and functions for the buf kmem cache.
972 */
973
974 static kmem_cache_t *hdr_full_cache;
975 static kmem_cache_t *hdr_full_crypt_cache;
976 static kmem_cache_t *hdr_l2only_cache;
977 static kmem_cache_t *buf_cache;
978
979 static void
980 buf_fini(void)
981 {
982 int i;
983
984 kmem_free(buf_hash_table.ht_table,
985 (buf_hash_table.ht_mask + 1) * sizeof (void *));
986 for (i = 0; i < BUF_LOCKS; i++)
987 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
988 kmem_cache_destroy(hdr_full_cache);
989 kmem_cache_destroy(hdr_full_crypt_cache);
990 kmem_cache_destroy(hdr_l2only_cache);
991 kmem_cache_destroy(buf_cache);
992 }
993
994 /*
995 * Constructor callback - called when the cache is empty
996 * and a new buf is requested.
997 */
998 /* ARGSUSED */
999 static int
1000 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1001 {
1002 arc_buf_hdr_t *hdr = vbuf;
1003
1004 bzero(hdr, HDR_FULL_SIZE);
1005 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
1006 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1007 zfs_refcount_create(&hdr->b_l1hdr.b_refcnt);
1008 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1009 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1010 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1011
1012 return (0);
1013 }
1014
1015 /* ARGSUSED */
1016 static int
1017 hdr_full_crypt_cons(void *vbuf, void *unused, int kmflag)
1018 {
1019 arc_buf_hdr_t *hdr = vbuf;
1020
1021 (void) hdr_full_cons(vbuf, unused, kmflag);
1022 bzero(&hdr->b_crypt_hdr, sizeof (hdr->b_crypt_hdr));
1023 arc_space_consume(sizeof (hdr->b_crypt_hdr), ARC_SPACE_HDRS);
1024
1025 return (0);
1026 }
1027
1028 /* ARGSUSED */
1029 static int
1030 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1031 {
1032 arc_buf_hdr_t *hdr = vbuf;
1033
1034 bzero(hdr, HDR_L2ONLY_SIZE);
1035 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1036
1037 return (0);
1038 }
1039
1040 /* ARGSUSED */
1041 static int
1042 buf_cons(void *vbuf, void *unused, int kmflag)
1043 {
1044 arc_buf_t *buf = vbuf;
1045
1046 bzero(buf, sizeof (arc_buf_t));
1047 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1048 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1049
1050 return (0);
1051 }
1052
1053 /*
1054 * Destructor callback - called when a cached buf is
1055 * no longer required.
1056 */
1057 /* ARGSUSED */
1058 static void
1059 hdr_full_dest(void *vbuf, void *unused)
1060 {
1061 arc_buf_hdr_t *hdr = vbuf;
1062
1063 ASSERT(HDR_EMPTY(hdr));
1064 cv_destroy(&hdr->b_l1hdr.b_cv);
1065 zfs_refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1066 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1067 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1068 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1069 }
1070
1071 /* ARGSUSED */
1072 static void
1073 hdr_full_crypt_dest(void *vbuf, void *unused)
1074 {
1075 arc_buf_hdr_t *hdr = vbuf;
1076
1077 hdr_full_dest(hdr, unused);
1078 arc_space_return(sizeof (hdr->b_crypt_hdr), ARC_SPACE_HDRS);
1079 }
1080
1081 /* ARGSUSED */
1082 static void
1083 hdr_l2only_dest(void *vbuf, void *unused)
1084 {
1085 arc_buf_hdr_t *hdr = vbuf;
1086
1087 ASSERT(HDR_EMPTY(hdr));
1088 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1089 }
1090
1091 /* ARGSUSED */
1092 static void
1093 buf_dest(void *vbuf, void *unused)
1094 {
1095 arc_buf_t *buf = vbuf;
1096
1097 mutex_destroy(&buf->b_evict_lock);
1098 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1099 }
1100
1101 /*
1102 * Reclaim callback -- invoked when memory is low.
1103 */
1104 /* ARGSUSED */
1105 static void
1106 hdr_recl(void *unused)
1107 {
1108 dprintf("hdr_recl called\n");
1109 /*
1110 * umem calls the reclaim func when we destroy the buf cache,
1111 * which is after we do arc_fini().
1112 */
1113 if (arc_initialized)
1114 zthr_wakeup(arc_reap_zthr);
1115 }
1116
1117 static void
1118 buf_init(void)
1119 {
1120 uint64_t *ct;
1121 uint64_t hsize = 1ULL << 12;
1122 int i, j;
1123
1124 /*
1125 * The hash table is big enough to fill all of physical memory
1126 * with an average block size of zfs_arc_average_blocksize (default 8K).
1127 * By default, the table will take up
1128 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1129 */
1130 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
1131 hsize <<= 1;
1132 retry:
1133 buf_hash_table.ht_mask = hsize - 1;
1134 buf_hash_table.ht_table =
1135 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1136 if (buf_hash_table.ht_table == NULL) {
1137 ASSERT(hsize > (1ULL << 8));
1138 hsize >>= 1;
1139 goto retry;
1140 }
1141
1142 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1143 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1144 hdr_full_crypt_cache = kmem_cache_create("arc_buf_hdr_t_full_crypt",
1145 HDR_FULL_CRYPT_SIZE, 0, hdr_full_crypt_cons, hdr_full_crypt_dest,
1146 hdr_recl, NULL, NULL, 0);
1147 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1148 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1149 NULL, NULL, 0);
1150 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1151 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1152
1153 for (i = 0; i < 256; i++)
1154 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1155 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1156
1157 for (i = 0; i < BUF_LOCKS; i++) {
1158 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1159 NULL, MUTEX_DEFAULT, NULL);
1160 }
1161 }
1162
1163 /*
1164 * This is the size that the buf occupies in memory. If the buf is compressed,
1165 * it will correspond to the compressed size. You should use this method of
1166 * getting the buf size unless you explicitly need the logical size.
1167 */
1168 int32_t
1169 arc_buf_size(arc_buf_t *buf)
1170 {
1171 return (ARC_BUF_COMPRESSED(buf) ?
1172 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
1173 }
1174
1175 int32_t
1176 arc_buf_lsize(arc_buf_t *buf)
1177 {
1178 return (HDR_GET_LSIZE(buf->b_hdr));
1179 }
1180
1181 /*
1182 * This function will return B_TRUE if the buffer is encrypted in memory.
1183 * This buffer can be decrypted by calling arc_untransform().
1184 */
1185 boolean_t
1186 arc_is_encrypted(arc_buf_t *buf)
1187 {
1188 return (ARC_BUF_ENCRYPTED(buf) != 0);
1189 }
1190
1191 /*
1192 * Returns B_TRUE if the buffer represents data that has not had its MAC
1193 * verified yet.
1194 */
1195 boolean_t
1196 arc_is_unauthenticated(arc_buf_t *buf)
1197 {
1198 return (HDR_NOAUTH(buf->b_hdr) != 0);
1199 }
1200
1201 void
1202 arc_get_raw_params(arc_buf_t *buf, boolean_t *byteorder, uint8_t *salt,
1203 uint8_t *iv, uint8_t *mac)
1204 {
1205 arc_buf_hdr_t *hdr = buf->b_hdr;
1206
1207 ASSERT(HDR_PROTECTED(hdr));
1208
1209 bcopy(hdr->b_crypt_hdr.b_salt, salt, ZIO_DATA_SALT_LEN);
1210 bcopy(hdr->b_crypt_hdr.b_iv, iv, ZIO_DATA_IV_LEN);
1211 bcopy(hdr->b_crypt_hdr.b_mac, mac, ZIO_DATA_MAC_LEN);
1212 *byteorder = (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ?
1213 /* CONSTCOND */
1214 ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER;
1215 }
1216
1217 /*
1218 * Indicates how this buffer is compressed in memory. If it is not compressed
1219 * the value will be ZIO_COMPRESS_OFF. It can be made normally readable with
1220 * arc_untransform() as long as it is also unencrypted.
1221 */
1222 enum zio_compress
1223 arc_get_compression(arc_buf_t *buf)
1224 {
1225 return (ARC_BUF_COMPRESSED(buf) ?
1226 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
1227 }
1228
1229 #define ARC_MINTIME (hz>>4) /* 62 ms */
1230
1231 /*
1232 * Return the compression algorithm used to store this data in the ARC. If ARC
1233 * compression is enabled or this is an encrypted block, this will be the same
1234 * as what's used to store it on-disk. Otherwise, this will be ZIO_COMPRESS_OFF.
1235 */
1236 static inline enum zio_compress
1237 arc_hdr_get_compress(arc_buf_hdr_t *hdr)
1238 {
1239 return (HDR_COMPRESSION_ENABLED(hdr) ?
1240 HDR_GET_COMPRESS(hdr) : ZIO_COMPRESS_OFF);
1241 }
1242
1243 static inline boolean_t
1244 arc_buf_is_shared(arc_buf_t *buf)
1245 {
1246 boolean_t shared = (buf->b_data != NULL &&
1247 buf->b_hdr->b_l1hdr.b_pabd != NULL &&
1248 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
1249 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
1250 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
1251 IMPLY(shared, ARC_BUF_SHARED(buf));
1252 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
1253
1254 /*
1255 * It would be nice to assert arc_can_share() too, but the "hdr isn't
1256 * already being shared" requirement prevents us from doing that.
1257 */
1258
1259 return (shared);
1260 }
1261
1262 /*
1263 * Free the checksum associated with this header. If there is no checksum, this
1264 * is a no-op.
1265 */
1266 static inline void
1267 arc_cksum_free(arc_buf_hdr_t *hdr)
1268 {
1269 ASSERT(HDR_HAS_L1HDR(hdr));
1270
1271 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1272 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1273 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
1274 hdr->b_l1hdr.b_freeze_cksum = NULL;
1275 }
1276 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1277 }
1278
1279 /*
1280 * Return true iff at least one of the bufs on hdr is not compressed.
1281 * Encrypted buffers count as compressed.
1282 */
1283 static boolean_t
1284 arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
1285 {
1286 ASSERT(hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY_OR_LOCKED(hdr));
1287
1288 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
1289 if (!ARC_BUF_COMPRESSED(b)) {
1290 return (B_TRUE);
1291 }
1292 }
1293 return (B_FALSE);
1294 }
1295
1296 /*
1297 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
1298 * matches the checksum that is stored in the hdr. If there is no checksum,
1299 * or if the buf is compressed, this is a no-op.
1300 */
1301 static void
1302 arc_cksum_verify(arc_buf_t *buf)
1303 {
1304 arc_buf_hdr_t *hdr = buf->b_hdr;
1305 zio_cksum_t zc;
1306
1307 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1308 return;
1309
1310 if (ARC_BUF_COMPRESSED(buf))
1311 return;
1312
1313 ASSERT(HDR_HAS_L1HDR(hdr));
1314
1315 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1316
1317 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
1318 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1319 return;
1320 }
1321
1322 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
1323 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
1324 panic("buffer modified while frozen!");
1325 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1326 }
1327
1328 /*
1329 * This function makes the assumption that data stored in the L2ARC
1330 * will be transformed exactly as it is in the main pool. Because of
1331 * this we can verify the checksum against the reading process's bp.
1332 */
1333 static boolean_t
1334 arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
1335 {
1336 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp);
1337 boolean_t valid_cksum;
1338
1339 ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
1340 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
1341
1342 /*
1343 * We rely on the blkptr's checksum to determine if the block
1344 * is valid or not. When compressed arc is enabled, the l2arc
1345 * writes the block to the l2arc just as it appears in the pool.
1346 * This allows us to use the blkptr's checksum to validate the
1347 * data that we just read off of the l2arc without having to store
1348 * a separate checksum in the arc_buf_hdr_t. However, if compressed
1349 * arc is disabled, then the data written to the l2arc is always
1350 * uncompressed and won't match the block as it exists in the main
1351 * pool. When this is the case, we must first compress it if it is
1352 * compressed on the main pool before we can validate the checksum.
1353 */
1354 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) {
1355 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1356 uint64_t lsize = HDR_GET_LSIZE(hdr);
1357 uint64_t csize;
1358
1359 abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE);
1360 csize = zio_compress_data(compress, zio->io_abd,
1361 abd_to_buf(cdata), lsize);
1362
1363 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr));
1364 if (csize < HDR_GET_PSIZE(hdr)) {
1365 /*
1366 * Compressed blocks are always a multiple of the
1367 * smallest ashift in the pool. Ideally, we would
1368 * like to round up the csize to the next
1369 * spa_min_ashift but that value may have changed
1370 * since the block was last written. Instead,
1371 * we rely on the fact that the hdr's psize
1372 * was set to the psize of the block when it was
1373 * last written. We set the csize to that value
1374 * and zero out any part that should not contain
1375 * data.
1376 */
1377 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize);
1378 csize = HDR_GET_PSIZE(hdr);
1379 }
1380 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL);
1381 }
1382
1383 /*
1384 * Block pointers always store the checksum for the logical data.
1385 * If the block pointer has the gang bit set, then the checksum
1386 * it represents is for the reconstituted data and not for an
1387 * individual gang member. The zio pipeline, however, must be able to
1388 * determine the checksum of each of the gang constituents so it
1389 * treats the checksum comparison differently than what we need
1390 * for l2arc blocks. This prevents us from using the
1391 * zio_checksum_error() interface directly. Instead we must call the
1392 * zio_checksum_error_impl() so that we can ensure the checksum is
1393 * generated using the correct checksum algorithm and accounts for the
1394 * logical I/O size and not just a gang fragment.
1395 */
1396 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
1397 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
1398 zio->io_offset, NULL) == 0);
1399 zio_pop_transforms(zio);
1400 return (valid_cksum);
1401 }
1402
1403 /*
1404 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
1405 * checksum and attaches it to the buf's hdr so that we can ensure that the buf
1406 * isn't modified later on. If buf is compressed or there is already a checksum
1407 * on the hdr, this is a no-op (we only checksum uncompressed bufs).
1408 */
1409 static void
1410 arc_cksum_compute(arc_buf_t *buf)
1411 {
1412 arc_buf_hdr_t *hdr = buf->b_hdr;
1413
1414 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1415 return;
1416
1417 ASSERT(HDR_HAS_L1HDR(hdr));
1418
1419 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1420 if (hdr->b_l1hdr.b_freeze_cksum != NULL || ARC_BUF_COMPRESSED(buf)) {
1421 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1422 return;
1423 }
1424
1425 ASSERT(!ARC_BUF_ENCRYPTED(buf));
1426 ASSERT(!ARC_BUF_COMPRESSED(buf));
1427 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
1428 KM_SLEEP);
1429 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
1430 hdr->b_l1hdr.b_freeze_cksum);
1431 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1432 arc_buf_watch(buf);
1433 }
1434
1435 #ifndef _KERNEL
1436 typedef struct procctl {
1437 long cmd;
1438 prwatch_t prwatch;
1439 } procctl_t;
1440 #endif
1441
1442 /* ARGSUSED */
1443 static void
1444 arc_buf_unwatch(arc_buf_t *buf)
1445 {
1446 #ifndef _KERNEL
1447 if (arc_watch) {
1448 int result;
1449 procctl_t ctl;
1450 ctl.cmd = PCWATCH;
1451 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1452 ctl.prwatch.pr_size = 0;
1453 ctl.prwatch.pr_wflags = 0;
1454 result = write(arc_procfd, &ctl, sizeof (ctl));
1455 ASSERT3U(result, ==, sizeof (ctl));
1456 }
1457 #endif
1458 }
1459
1460 /* ARGSUSED */
1461 static void
1462 arc_buf_watch(arc_buf_t *buf)
1463 {
1464 #ifndef _KERNEL
1465 if (arc_watch) {
1466 int result;
1467 procctl_t ctl;
1468 ctl.cmd = PCWATCH;
1469 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1470 ctl.prwatch.pr_size = arc_buf_size(buf);
1471 ctl.prwatch.pr_wflags = WA_WRITE;
1472 result = write(arc_procfd, &ctl, sizeof (ctl));
1473 ASSERT3U(result, ==, sizeof (ctl));
1474 }
1475 #endif
1476 }
1477
1478 static arc_buf_contents_t
1479 arc_buf_type(arc_buf_hdr_t *hdr)
1480 {
1481 arc_buf_contents_t type;
1482 if (HDR_ISTYPE_METADATA(hdr)) {
1483 type = ARC_BUFC_METADATA;
1484 } else {
1485 type = ARC_BUFC_DATA;
1486 }
1487 VERIFY3U(hdr->b_type, ==, type);
1488 return (type);
1489 }
1490
1491 boolean_t
1492 arc_is_metadata(arc_buf_t *buf)
1493 {
1494 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
1495 }
1496
1497 static uint32_t
1498 arc_bufc_to_flags(arc_buf_contents_t type)
1499 {
1500 switch (type) {
1501 case ARC_BUFC_DATA:
1502 /* metadata field is 0 if buffer contains normal data */
1503 return (0);
1504 case ARC_BUFC_METADATA:
1505 return (ARC_FLAG_BUFC_METADATA);
1506 default:
1507 break;
1508 }
1509 panic("undefined ARC buffer type!");
1510 return ((uint32_t)-1);
1511 }
1512
1513 void
1514 arc_buf_thaw(arc_buf_t *buf)
1515 {
1516 arc_buf_hdr_t *hdr = buf->b_hdr;
1517
1518 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
1519 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1520
1521 arc_cksum_verify(buf);
1522
1523 /*
1524 * Compressed buffers do not manipulate the b_freeze_cksum.
1525 */
1526 if (ARC_BUF_COMPRESSED(buf))
1527 return;
1528
1529 ASSERT(HDR_HAS_L1HDR(hdr));
1530 arc_cksum_free(hdr);
1531
1532 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1533 #ifdef ZFS_DEBUG
1534 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1535 if (hdr->b_l1hdr.b_thawed != NULL)
1536 kmem_free(hdr->b_l1hdr.b_thawed, 1);
1537 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
1538 }
1539 #endif
1540
1541 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1542
1543 arc_buf_unwatch(buf);
1544 }
1545
1546 void
1547 arc_buf_freeze(arc_buf_t *buf)
1548 {
1549 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1550 return;
1551
1552 if (ARC_BUF_COMPRESSED(buf))
1553 return;
1554
1555 ASSERT(HDR_HAS_L1HDR(buf->b_hdr));
1556 arc_cksum_compute(buf);
1557 }
1558
1559 /*
1560 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
1561 * the following functions should be used to ensure that the flags are
1562 * updated in a thread-safe way. When manipulating the flags either
1563 * the hash_lock must be held or the hdr must be undiscoverable. This
1564 * ensures that we're not racing with any other threads when updating
1565 * the flags.
1566 */
1567 static inline void
1568 arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
1569 {
1570 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1571 hdr->b_flags |= flags;
1572 }
1573
1574 static inline void
1575 arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
1576 {
1577 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1578 hdr->b_flags &= ~flags;
1579 }
1580
1581 /*
1582 * Setting the compression bits in the arc_buf_hdr_t's b_flags is
1583 * done in a special way since we have to clear and set bits
1584 * at the same time. Consumers that wish to set the compression bits
1585 * must use this function to ensure that the flags are updated in
1586 * thread-safe manner.
1587 */
1588 static void
1589 arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
1590 {
1591 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1592
1593 /*
1594 * Holes and embedded blocks will always have a psize = 0 so
1595 * we ignore the compression of the blkptr and set the
1596 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF.
1597 * Holes and embedded blocks remain anonymous so we don't
1598 * want to uncompress them. Mark them as uncompressed.
1599 */
1600 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
1601 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
1602 ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
1603 } else {
1604 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
1605 ASSERT(HDR_COMPRESSION_ENABLED(hdr));
1606 }
1607
1608 HDR_SET_COMPRESS(hdr, cmp);
1609 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
1610 }
1611
1612 /*
1613 * Looks for another buf on the same hdr which has the data decompressed, copies
1614 * from it, and returns true. If no such buf exists, returns false.
1615 */
1616 static boolean_t
1617 arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
1618 {
1619 arc_buf_hdr_t *hdr = buf->b_hdr;
1620 boolean_t copied = B_FALSE;
1621
1622 ASSERT(HDR_HAS_L1HDR(hdr));
1623 ASSERT3P(buf->b_data, !=, NULL);
1624 ASSERT(!ARC_BUF_COMPRESSED(buf));
1625
1626 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
1627 from = from->b_next) {
1628 /* can't use our own data buffer */
1629 if (from == buf) {
1630 continue;
1631 }
1632
1633 if (!ARC_BUF_COMPRESSED(from)) {
1634 bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
1635 copied = B_TRUE;
1636 break;
1637 }
1638 }
1639
1640 /*
1641 * Note: With encryption support, the following assertion is no longer
1642 * necessarily valid. If we receive two back to back raw snapshots
1643 * (send -w), the second receive can use a hdr with a cksum already
1644 * calculated. This happens via:
1645 * dmu_recv_stream() -> receive_read_record() -> arc_loan_raw_buf()
1646 * The rsend/send_mixed_raw test case exercises this code path.
1647 *
1648 * There were no decompressed bufs, so there should not be a
1649 * checksum on the hdr either.
1650 * EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
1651 */
1652
1653 return (copied);
1654 }
1655
1656 /*
1657 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
1658 */
1659 static uint64_t
1660 arc_hdr_size(arc_buf_hdr_t *hdr)
1661 {
1662 uint64_t size;
1663
1664 if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF &&
1665 HDR_GET_PSIZE(hdr) > 0) {
1666 size = HDR_GET_PSIZE(hdr);
1667 } else {
1668 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
1669 size = HDR_GET_LSIZE(hdr);
1670 }
1671 return (size);
1672 }
1673
1674 static int
1675 arc_hdr_authenticate(arc_buf_hdr_t *hdr, spa_t *spa, uint64_t dsobj)
1676 {
1677 int ret;
1678 uint64_t csize;
1679 uint64_t lsize = HDR_GET_LSIZE(hdr);
1680 uint64_t psize = HDR_GET_PSIZE(hdr);
1681 void *tmpbuf = NULL;
1682 abd_t *abd = hdr->b_l1hdr.b_pabd;
1683
1684 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1685 ASSERT(HDR_AUTHENTICATED(hdr));
1686 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
1687
1688 /*
1689 * The MAC is calculated on the compressed data that is stored on disk.
1690 * However, if compressed arc is disabled we will only have the
1691 * decompressed data available to us now. Compress it into a temporary
1692 * abd so we can verify the MAC. The performance overhead of this will
1693 * be relatively low, since most objects in an encrypted objset will
1694 * be encrypted (instead of authenticated) anyway.
1695 */
1696 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
1697 !HDR_COMPRESSION_ENABLED(hdr)) {
1698 tmpbuf = zio_buf_alloc(lsize);
1699 abd = abd_get_from_buf(tmpbuf, lsize);
1700 abd_take_ownership_of_buf(abd, B_TRUE);
1701
1702 csize = zio_compress_data(HDR_GET_COMPRESS(hdr),
1703 hdr->b_l1hdr.b_pabd, tmpbuf, lsize);
1704 ASSERT3U(csize, <=, psize);
1705 abd_zero_off(abd, csize, psize - csize);
1706 }
1707
1708 /*
1709 * Authentication is best effort. We authenticate whenever the key is
1710 * available. If we succeed we clear ARC_FLAG_NOAUTH.
1711 */
1712 if (hdr->b_crypt_hdr.b_ot == DMU_OT_OBJSET) {
1713 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1714 ASSERT3U(lsize, ==, psize);
1715 ret = spa_do_crypt_objset_mac_abd(B_FALSE, spa, dsobj, abd,
1716 psize, hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
1717 } else {
1718 ret = spa_do_crypt_mac_abd(B_FALSE, spa, dsobj, abd, psize,
1719 hdr->b_crypt_hdr.b_mac);
1720 }
1721
1722 if (ret == 0)
1723 arc_hdr_clear_flags(hdr, ARC_FLAG_NOAUTH);
1724 else if (ret != ENOENT)
1725 goto error;
1726
1727 if (tmpbuf != NULL)
1728 abd_free(abd);
1729
1730 return (0);
1731
1732 error:
1733 if (tmpbuf != NULL)
1734 abd_free(abd);
1735
1736 return (ret);
1737 }
1738
1739 /*
1740 * This function will take a header that only has raw encrypted data in
1741 * b_crypt_hdr.b_rabd and decrypt it into a new buffer which is stored in
1742 * b_l1hdr.b_pabd. If designated in the header flags, this function will
1743 * also decompress the data.
1744 */
1745 static int
1746 arc_hdr_decrypt(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb)
1747 {
1748 int ret;
1749 abd_t *cabd = NULL;
1750 void *tmp = NULL;
1751 boolean_t no_crypt = B_FALSE;
1752 boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
1753
1754 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1755 ASSERT(HDR_ENCRYPTED(hdr));
1756
1757 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT);
1758
1759 ret = spa_do_crypt_abd(B_FALSE, spa, zb, hdr->b_crypt_hdr.b_ot,
1760 B_FALSE, bswap, hdr->b_crypt_hdr.b_salt, hdr->b_crypt_hdr.b_iv,
1761 hdr->b_crypt_hdr.b_mac, HDR_GET_PSIZE(hdr), hdr->b_l1hdr.b_pabd,
1762 hdr->b_crypt_hdr.b_rabd, &no_crypt);
1763 if (ret != 0)
1764 goto error;
1765
1766 if (no_crypt) {
1767 abd_copy(hdr->b_l1hdr.b_pabd, hdr->b_crypt_hdr.b_rabd,
1768 HDR_GET_PSIZE(hdr));
1769 }
1770
1771 /*
1772 * If this header has disabled arc compression but the b_pabd is
1773 * compressed after decrypting it, we need to decompress the newly
1774 * decrypted data.
1775 */
1776 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
1777 !HDR_COMPRESSION_ENABLED(hdr)) {
1778 /*
1779 * We want to make sure that we are correctly honoring the
1780 * zfs_abd_scatter_enabled setting, so we allocate an abd here
1781 * and then loan a buffer from it, rather than allocating a
1782 * linear buffer and wrapping it in an abd later.
1783 */
1784 cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr, B_TRUE);
1785 tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr));
1786
1787 ret = zio_decompress_data(HDR_GET_COMPRESS(hdr),
1788 hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr),
1789 HDR_GET_LSIZE(hdr));
1790 if (ret != 0) {
1791 abd_return_buf(cabd, tmp, arc_hdr_size(hdr));
1792 goto error;
1793 }
1794
1795 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
1796 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
1797 arc_hdr_size(hdr), hdr);
1798 hdr->b_l1hdr.b_pabd = cabd;
1799 }
1800
1801 return (0);
1802
1803 error:
1804 arc_hdr_free_pabd(hdr, B_FALSE);
1805 if (cabd != NULL)
1806 arc_free_data_buf(hdr, cabd, arc_hdr_size(hdr), hdr);
1807
1808 return (ret);
1809 }
1810
1811 /*
1812 * This function is called during arc_buf_fill() to prepare the header's
1813 * abd plaintext pointer for use. This involves authenticated protected
1814 * data and decrypting encrypted data into the plaintext abd.
1815 */
1816 static int
1817 arc_fill_hdr_crypt(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, spa_t *spa,
1818 const zbookmark_phys_t *zb, boolean_t noauth)
1819 {
1820 int ret;
1821
1822 ASSERT(HDR_PROTECTED(hdr));
1823
1824 if (hash_lock != NULL)
1825 mutex_enter(hash_lock);
1826
1827 if (HDR_NOAUTH(hdr) && !noauth) {
1828 /*
1829 * The caller requested authenticated data but our data has
1830 * not been authenticated yet. Verify the MAC now if we can.
1831 */
1832 ret = arc_hdr_authenticate(hdr, spa, zb->zb_objset);
1833 if (ret != 0)
1834 goto error;
1835 } else if (HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd == NULL) {
1836 /*
1837 * If we only have the encrypted version of the data, but the
1838 * unencrypted version was requested we take this opportunity
1839 * to store the decrypted version in the header for future use.
1840 */
1841 ret = arc_hdr_decrypt(hdr, spa, zb);
1842 if (ret != 0)
1843 goto error;
1844 }
1845
1846 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
1847
1848 if (hash_lock != NULL)
1849 mutex_exit(hash_lock);
1850
1851 return (0);
1852
1853 error:
1854 if (hash_lock != NULL)
1855 mutex_exit(hash_lock);
1856
1857 return (ret);
1858 }
1859
1860 /*
1861 * This function is used by the dbuf code to decrypt bonus buffers in place.
1862 * The dbuf code itself doesn't have any locking for decrypting a shared dnode
1863 * block, so we use the hash lock here to protect against concurrent calls to
1864 * arc_buf_fill().
1865 */
1866 /* ARGSUSED */
1867 static void
1868 arc_buf_untransform_in_place(arc_buf_t *buf, kmutex_t *hash_lock)
1869 {
1870 arc_buf_hdr_t *hdr = buf->b_hdr;
1871
1872 ASSERT(HDR_ENCRYPTED(hdr));
1873 ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE);
1874 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1875 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
1876
1877 zio_crypt_copy_dnode_bonus(hdr->b_l1hdr.b_pabd, buf->b_data,
1878 arc_buf_size(buf));
1879 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
1880 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
1881 hdr->b_crypt_hdr.b_ebufcnt -= 1;
1882 }
1883
1884 /*
1885 * Given a buf that has a data buffer attached to it, this function will
1886 * efficiently fill the buf with data of the specified compression setting from
1887 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
1888 * are already sharing a data buf, no copy is performed.
1889 *
1890 * If the buf is marked as compressed but uncompressed data was requested, this
1891 * will allocate a new data buffer for the buf, remove that flag, and fill the
1892 * buf with uncompressed data. You can't request a compressed buf on a hdr with
1893 * uncompressed data, and (since we haven't added support for it yet) if you
1894 * want compressed data your buf must already be marked as compressed and have
1895 * the correct-sized data buffer.
1896 */
1897 static int
1898 arc_buf_fill(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
1899 arc_fill_flags_t flags)
1900 {
1901 int error = 0;
1902 arc_buf_hdr_t *hdr = buf->b_hdr;
1903 boolean_t hdr_compressed =
1904 (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
1905 boolean_t compressed = (flags & ARC_FILL_COMPRESSED) != 0;
1906 boolean_t encrypted = (flags & ARC_FILL_ENCRYPTED) != 0;
1907 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
1908 kmutex_t *hash_lock = (flags & ARC_FILL_LOCKED) ? NULL : HDR_LOCK(hdr);
1909
1910 ASSERT3P(buf->b_data, !=, NULL);
1911 IMPLY(compressed, hdr_compressed || ARC_BUF_ENCRYPTED(buf));
1912 IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
1913 IMPLY(encrypted, HDR_ENCRYPTED(hdr));
1914 IMPLY(encrypted, ARC_BUF_ENCRYPTED(buf));
1915 IMPLY(encrypted, ARC_BUF_COMPRESSED(buf));
1916 IMPLY(encrypted, !ARC_BUF_SHARED(buf));
1917
1918 /*
1919 * If the caller wanted encrypted data we just need to copy it from
1920 * b_rabd and potentially byteswap it. We won't be able to do any
1921 * further transforms on it.
1922 */
1923 if (encrypted) {
1924 ASSERT(HDR_HAS_RABD(hdr));
1925 abd_copy_to_buf(buf->b_data, hdr->b_crypt_hdr.b_rabd,
1926 HDR_GET_PSIZE(hdr));
1927 goto byteswap;
1928 }
1929
1930 /*
1931 * Adjust encrypted and authenticated headers to accomodate
1932 * the request if needed. Dnode blocks (ARC_FILL_IN_PLACE) are
1933 * allowed to fail decryption due to keys not being loaded
1934 * without being marked as an IO error.
1935 */
1936 if (HDR_PROTECTED(hdr)) {
1937 error = arc_fill_hdr_crypt(hdr, hash_lock, spa,
1938 zb, !!(flags & ARC_FILL_NOAUTH));
1939 if (error == EACCES && (flags & ARC_FILL_IN_PLACE) != 0) {
1940 return (error);
1941 } else if (error != 0) {
1942 if (hash_lock != NULL)
1943 mutex_enter(hash_lock);
1944 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
1945 if (hash_lock != NULL)
1946 mutex_exit(hash_lock);
1947 return (error);
1948 }
1949 }
1950
1951 /*
1952 * There is a special case here for dnode blocks which are
1953 * decrypting their bonus buffers. These blocks may request to
1954 * be decrypted in-place. This is necessary because there may
1955 * be many dnodes pointing into this buffer and there is
1956 * currently no method to synchronize replacing the backing
1957 * b_data buffer and updating all of the pointers. Here we use
1958 * the hash lock to ensure there are no races. If the need
1959 * arises for other types to be decrypted in-place, they must
1960 * add handling here as well.
1961 */
1962 if ((flags & ARC_FILL_IN_PLACE) != 0) {
1963 ASSERT(!hdr_compressed);
1964 ASSERT(!compressed);
1965 ASSERT(!encrypted);
1966
1967 if (HDR_ENCRYPTED(hdr) && ARC_BUF_ENCRYPTED(buf)) {
1968 ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE);
1969
1970 if (hash_lock != NULL)
1971 mutex_enter(hash_lock);
1972 arc_buf_untransform_in_place(buf, hash_lock);
1973 if (hash_lock != NULL)
1974 mutex_exit(hash_lock);
1975
1976 /* Compute the hdr's checksum if necessary */
1977 arc_cksum_compute(buf);
1978 }
1979
1980 return (0);
1981 }
1982
1983 if (hdr_compressed == compressed) {
1984 if (!arc_buf_is_shared(buf)) {
1985 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
1986 arc_buf_size(buf));
1987 }
1988 } else {
1989 ASSERT(hdr_compressed);
1990 ASSERT(!compressed);
1991 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
1992
1993 /*
1994 * If the buf is sharing its data with the hdr, unlink it and
1995 * allocate a new data buffer for the buf.
1996 */
1997 if (arc_buf_is_shared(buf)) {
1998 ASSERT(ARC_BUF_COMPRESSED(buf));
1999
2000 /* We need to give the buf its own b_data */
2001 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2002 buf->b_data =
2003 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2004 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2005
2006 /* Previously overhead was 0; just add new overhead */
2007 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
2008 } else if (ARC_BUF_COMPRESSED(buf)) {
2009 /* We need to reallocate the buf's b_data */
2010 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
2011 buf);
2012 buf->b_data =
2013 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2014
2015 /* We increased the size of b_data; update overhead */
2016 ARCSTAT_INCR(arcstat_overhead_size,
2017 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
2018 }
2019
2020 /*
2021 * Regardless of the buf's previous compression settings, it
2022 * should not be compressed at the end of this function.
2023 */
2024 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
2025
2026 /*
2027 * Try copying the data from another buf which already has a
2028 * decompressed version. If that's not possible, it's time to
2029 * bite the bullet and decompress the data from the hdr.
2030 */
2031 if (arc_buf_try_copy_decompressed_data(buf)) {
2032 /* Skip byteswapping and checksumming (already done) */
2033 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL);
2034 return (0);
2035 } else {
2036 error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
2037 hdr->b_l1hdr.b_pabd, buf->b_data,
2038 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2039
2040 /*
2041 * Absent hardware errors or software bugs, this should
2042 * be impossible, but log it anyway so we can debug it.
2043 */
2044 if (error != 0) {
2045 zfs_dbgmsg(
2046 "hdr %p, compress %d, psize %d, lsize %d",
2047 hdr, arc_hdr_get_compress(hdr),
2048 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2049 if (hash_lock != NULL)
2050 mutex_enter(hash_lock);
2051 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
2052 if (hash_lock != NULL)
2053 mutex_exit(hash_lock);
2054 return (SET_ERROR(EIO));
2055 }
2056 }
2057 }
2058
2059 byteswap:
2060 /* Byteswap the buf's data if necessary */
2061 if (bswap != DMU_BSWAP_NUMFUNCS) {
2062 ASSERT(!HDR_SHARED_DATA(hdr));
2063 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
2064 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
2065 }
2066
2067 /* Compute the hdr's checksum if necessary */
2068 arc_cksum_compute(buf);
2069
2070 return (0);
2071 }
2072
2073 /*
2074 * If this function is being called to decrypt an encrypted buffer or verify an
2075 * authenticated one, the key must be loaded and a mapping must be made
2076 * available in the keystore via spa_keystore_create_mapping() or one of its
2077 * callers.
2078 */
2079 int
2080 arc_untransform(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
2081 boolean_t in_place)
2082 {
2083 int ret;
2084 arc_fill_flags_t flags = 0;
2085
2086 if (in_place)
2087 flags |= ARC_FILL_IN_PLACE;
2088
2089 ret = arc_buf_fill(buf, spa, zb, flags);
2090 if (ret == ECKSUM) {
2091 /*
2092 * Convert authentication and decryption errors to EIO
2093 * (and generate an ereport) before leaving the ARC.
2094 */
2095 ret = SET_ERROR(EIO);
2096 spa_log_error(spa, zb);
2097 (void) zfs_ereport_post(FM_EREPORT_ZFS_AUTHENTICATION,
2098 spa, NULL, zb, NULL, 0, 0);
2099 }
2100
2101 return (ret);
2102 }
2103
2104 /*
2105 * Increment the amount of evictable space in the arc_state_t's refcount.
2106 * We account for the space used by the hdr and the arc buf individually
2107 * so that we can add and remove them from the refcount individually.
2108 */
2109 static void
2110 arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
2111 {
2112 arc_buf_contents_t type = arc_buf_type(hdr);
2113
2114 ASSERT(HDR_HAS_L1HDR(hdr));
2115
2116 if (GHOST_STATE(state)) {
2117 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2118 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2119 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2120 ASSERT(!HDR_HAS_RABD(hdr));
2121 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2122 HDR_GET_LSIZE(hdr), hdr);
2123 return;
2124 }
2125
2126 ASSERT(!GHOST_STATE(state));
2127 if (hdr->b_l1hdr.b_pabd != NULL) {
2128 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2129 arc_hdr_size(hdr), hdr);
2130 }
2131 if (HDR_HAS_RABD(hdr)) {
2132 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2133 HDR_GET_PSIZE(hdr), hdr);
2134 }
2135 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2136 buf = buf->b_next) {
2137 if (arc_buf_is_shared(buf))
2138 continue;
2139 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2140 arc_buf_size(buf), buf);
2141 }
2142 }
2143
2144 /*
2145 * Decrement the amount of evictable space in the arc_state_t's refcount.
2146 * We account for the space used by the hdr and the arc buf individually
2147 * so that we can add and remove them from the refcount individually.
2148 */
2149 static void
2150 arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
2151 {
2152 arc_buf_contents_t type = arc_buf_type(hdr);
2153
2154 ASSERT(HDR_HAS_L1HDR(hdr));
2155
2156 if (GHOST_STATE(state)) {
2157 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2158 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2159 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2160 ASSERT(!HDR_HAS_RABD(hdr));
2161 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2162 HDR_GET_LSIZE(hdr), hdr);
2163 return;
2164 }
2165
2166 ASSERT(!GHOST_STATE(state));
2167 if (hdr->b_l1hdr.b_pabd != NULL) {
2168 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2169 arc_hdr_size(hdr), hdr);
2170 }
2171 if (HDR_HAS_RABD(hdr)) {
2172 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2173 HDR_GET_PSIZE(hdr), hdr);
2174 }
2175 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2176 buf = buf->b_next) {
2177 if (arc_buf_is_shared(buf))
2178 continue;
2179 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2180 arc_buf_size(buf), buf);
2181 }
2182 }
2183
2184 /*
2185 * Add a reference to this hdr indicating that someone is actively
2186 * referencing that memory. When the refcount transitions from 0 to 1,
2187 * we remove it from the respective arc_state_t list to indicate that
2188 * it is not evictable.
2189 */
2190 static void
2191 add_reference(arc_buf_hdr_t *hdr, void *tag)
2192 {
2193 ASSERT(HDR_HAS_L1HDR(hdr));
2194 if (!HDR_EMPTY(hdr) && !MUTEX_HELD(HDR_LOCK(hdr))) {
2195 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
2196 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2197 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2198 }
2199
2200 arc_state_t *state = hdr->b_l1hdr.b_state;
2201
2202 if ((zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
2203 (state != arc_anon)) {
2204 /* We don't use the L2-only state list. */
2205 if (state != arc_l2c_only) {
2206 multilist_remove(state->arcs_list[arc_buf_type(hdr)],
2207 hdr);
2208 arc_evictable_space_decrement(hdr, state);
2209 }
2210 /* remove the prefetch flag if we get a reference */
2211 if (HDR_HAS_L2HDR(hdr))
2212 l2arc_hdr_arcstats_decrement_state(hdr);
2213 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
2214 if (HDR_HAS_L2HDR(hdr))
2215 l2arc_hdr_arcstats_increment_state(hdr);
2216 }
2217 }
2218
2219 /*
2220 * Remove a reference from this hdr. When the reference transitions from
2221 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
2222 * list making it eligible for eviction.
2223 */
2224 static int
2225 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
2226 {
2227 int cnt;
2228 arc_state_t *state = hdr->b_l1hdr.b_state;
2229
2230 ASSERT(HDR_HAS_L1HDR(hdr));
2231 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
2232 ASSERT(!GHOST_STATE(state));
2233
2234 /*
2235 * arc_l2c_only counts as a ghost state so we don't need to explicitly
2236 * check to prevent usage of the arc_l2c_only list.
2237 */
2238 if (((cnt = zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
2239 (state != arc_anon)) {
2240 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
2241 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
2242 arc_evictable_space_increment(hdr, state);
2243 }
2244 return (cnt);
2245 }
2246
2247 /*
2248 * Move the supplied buffer to the indicated state. The hash lock
2249 * for the buffer must be held by the caller.
2250 */
2251 static void
2252 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
2253 kmutex_t *hash_lock)
2254 {
2255 arc_state_t *old_state;
2256 int64_t refcnt;
2257 uint32_t bufcnt;
2258 boolean_t update_old, update_new;
2259 arc_buf_contents_t buftype = arc_buf_type(hdr);
2260
2261 /*
2262 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
2263 * in arc_read() when bringing a buffer out of the L2ARC. However, the
2264 * L1 hdr doesn't always exist when we change state to arc_anon before
2265 * destroying a header, in which case reallocating to add the L1 hdr is
2266 * pointless.
2267 */
2268 if (HDR_HAS_L1HDR(hdr)) {
2269 old_state = hdr->b_l1hdr.b_state;
2270 refcnt = zfs_refcount_count(&hdr->b_l1hdr.b_refcnt);
2271 bufcnt = hdr->b_l1hdr.b_bufcnt;
2272
2273 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL ||
2274 HDR_HAS_RABD(hdr));
2275 } else {
2276 old_state = arc_l2c_only;
2277 refcnt = 0;
2278 bufcnt = 0;
2279 update_old = B_FALSE;
2280 }
2281 update_new = update_old;
2282
2283 ASSERT(MUTEX_HELD(hash_lock));
2284 ASSERT3P(new_state, !=, old_state);
2285 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
2286 ASSERT(old_state != arc_anon || bufcnt <= 1);
2287
2288 /*
2289 * If this buffer is evictable, transfer it from the
2290 * old state list to the new state list.
2291 */
2292 if (refcnt == 0) {
2293 if (old_state != arc_anon && old_state != arc_l2c_only) {
2294 ASSERT(HDR_HAS_L1HDR(hdr));
2295 multilist_remove(old_state->arcs_list[buftype], hdr);
2296
2297 if (GHOST_STATE(old_state)) {
2298 ASSERT0(bufcnt);
2299 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2300 update_old = B_TRUE;
2301 }
2302 arc_evictable_space_decrement(hdr, old_state);
2303 }
2304 if (new_state != arc_anon && new_state != arc_l2c_only) {
2305
2306 /*
2307 * An L1 header always exists here, since if we're
2308 * moving to some L1-cached state (i.e. not l2c_only or
2309 * anonymous), we realloc the header to add an L1hdr
2310 * beforehand.
2311 */
2312 ASSERT(HDR_HAS_L1HDR(hdr));
2313 multilist_insert(new_state->arcs_list[buftype], hdr);
2314
2315 if (GHOST_STATE(new_state)) {
2316 ASSERT0(bufcnt);
2317 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2318 update_new = B_TRUE;
2319 }
2320 arc_evictable_space_increment(hdr, new_state);
2321 }
2322 }
2323
2324 ASSERT(!HDR_EMPTY(hdr));
2325 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
2326 buf_hash_remove(hdr);
2327
2328 /* adjust state sizes (ignore arc_l2c_only) */
2329
2330 if (update_new && new_state != arc_l2c_only) {
2331 ASSERT(HDR_HAS_L1HDR(hdr));
2332 if (GHOST_STATE(new_state)) {
2333 ASSERT0(bufcnt);
2334
2335 /*
2336 * When moving a header to a ghost state, we first
2337 * remove all arc buffers. Thus, we'll have a
2338 * bufcnt of zero, and no arc buffer to use for
2339 * the reference. As a result, we use the arc
2340 * header pointer for the reference.
2341 */
2342 (void) zfs_refcount_add_many(&new_state->arcs_size,
2343 HDR_GET_LSIZE(hdr), hdr);
2344 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2345 ASSERT(!HDR_HAS_RABD(hdr));
2346 } else {
2347 uint32_t buffers = 0;
2348
2349 /*
2350 * Each individual buffer holds a unique reference,
2351 * thus we must remove each of these references one
2352 * at a time.
2353 */
2354 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2355 buf = buf->b_next) {
2356 ASSERT3U(bufcnt, !=, 0);
2357 buffers++;
2358
2359 /*
2360 * When the arc_buf_t is sharing the data
2361 * block with the hdr, the owner of the
2362 * reference belongs to the hdr. Only
2363 * add to the refcount if the arc_buf_t is
2364 * not shared.
2365 */
2366 if (arc_buf_is_shared(buf))
2367 continue;
2368
2369 (void) zfs_refcount_add_many(
2370 &new_state->arcs_size,
2371 arc_buf_size(buf), buf);
2372 }
2373 ASSERT3U(bufcnt, ==, buffers);
2374
2375 if (hdr->b_l1hdr.b_pabd != NULL) {
2376 (void) zfs_refcount_add_many(
2377 &new_state->arcs_size,
2378 arc_hdr_size(hdr), hdr);
2379 }
2380
2381 if (HDR_HAS_RABD(hdr)) {
2382 (void) zfs_refcount_add_many(
2383 &new_state->arcs_size,
2384 HDR_GET_PSIZE(hdr), hdr);
2385 }
2386 }
2387 }
2388
2389 if (update_old && old_state != arc_l2c_only) {
2390 ASSERT(HDR_HAS_L1HDR(hdr));
2391 if (GHOST_STATE(old_state)) {
2392 ASSERT0(bufcnt);
2393 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2394 ASSERT(!HDR_HAS_RABD(hdr));
2395
2396 /*
2397 * When moving a header off of a ghost state,
2398 * the header will not contain any arc buffers.
2399 * We use the arc header pointer for the reference
2400 * which is exactly what we did when we put the
2401 * header on the ghost state.
2402 */
2403
2404 (void) zfs_refcount_remove_many(&old_state->arcs_size,
2405 HDR_GET_LSIZE(hdr), hdr);
2406 } else {
2407 uint32_t buffers = 0;
2408
2409 /*
2410 * Each individual buffer holds a unique reference,
2411 * thus we must remove each of these references one
2412 * at a time.
2413 */
2414 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2415 buf = buf->b_next) {
2416 ASSERT3U(bufcnt, !=, 0);
2417 buffers++;
2418
2419 /*
2420 * When the arc_buf_t is sharing the data
2421 * block with the hdr, the owner of the
2422 * reference belongs to the hdr. Only
2423 * add to the refcount if the arc_buf_t is
2424 * not shared.
2425 */
2426 if (arc_buf_is_shared(buf))
2427 continue;
2428
2429 (void) zfs_refcount_remove_many(
2430 &old_state->arcs_size, arc_buf_size(buf),
2431 buf);
2432 }
2433 ASSERT3U(bufcnt, ==, buffers);
2434 ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
2435 HDR_HAS_RABD(hdr));
2436
2437 if (hdr->b_l1hdr.b_pabd != NULL) {
2438 (void) zfs_refcount_remove_many(
2439 &old_state->arcs_size, arc_hdr_size(hdr),
2440 hdr);
2441 }
2442
2443 if (HDR_HAS_RABD(hdr)) {
2444 (void) zfs_refcount_remove_many(
2445 &old_state->arcs_size, HDR_GET_PSIZE(hdr),
2446 hdr);
2447 }
2448 }
2449 }
2450
2451 if (HDR_HAS_L1HDR(hdr)) {
2452 hdr->b_l1hdr.b_state = new_state;
2453
2454 if (HDR_HAS_L2HDR(hdr) && new_state != arc_l2c_only) {
2455 l2arc_hdr_arcstats_decrement_state(hdr);
2456 hdr->b_l2hdr.b_arcs_state = new_state->arcs_state;
2457 l2arc_hdr_arcstats_increment_state(hdr);
2458 }
2459 }
2460
2461 /*
2462 * L2 headers should never be on the L2 state list since they don't
2463 * have L1 headers allocated.
2464 */
2465 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
2466 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
2467 }
2468
2469 void
2470 arc_space_consume(uint64_t space, arc_space_type_t type)
2471 {
2472 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2473
2474 switch (type) {
2475 case ARC_SPACE_DATA:
2476 aggsum_add(&astat_data_size, space);
2477 break;
2478 case ARC_SPACE_META:
2479 aggsum_add(&astat_metadata_size, space);
2480 break;
2481 case ARC_SPACE_OTHER:
2482 aggsum_add(&astat_other_size, space);
2483 break;
2484 case ARC_SPACE_HDRS:
2485 aggsum_add(&astat_hdr_size, space);
2486 break;
2487 case ARC_SPACE_L2HDRS:
2488 aggsum_add(&astat_l2_hdr_size, space);
2489 break;
2490 }
2491
2492 if (type != ARC_SPACE_DATA)
2493 aggsum_add(&arc_meta_used, space);
2494
2495 aggsum_add(&arc_size, space);
2496 }
2497
2498 void
2499 arc_space_return(uint64_t space, arc_space_type_t type)
2500 {
2501 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2502
2503 switch (type) {
2504 case ARC_SPACE_DATA:
2505 aggsum_add(&astat_data_size, -space);
2506 break;
2507 case ARC_SPACE_META:
2508 aggsum_add(&astat_metadata_size, -space);
2509 break;
2510 case ARC_SPACE_OTHER:
2511 aggsum_add(&astat_other_size, -space);
2512 break;
2513 case ARC_SPACE_HDRS:
2514 aggsum_add(&astat_hdr_size, -space);
2515 break;
2516 case ARC_SPACE_L2HDRS:
2517 aggsum_add(&astat_l2_hdr_size, -space);
2518 break;
2519 }
2520
2521 if (type != ARC_SPACE_DATA) {
2522 ASSERT(aggsum_compare(&arc_meta_used, space) >= 0);
2523 /*
2524 * We use the upper bound here rather than the precise value
2525 * because the arc_meta_max value doesn't need to be
2526 * precise. It's only consumed by humans via arcstats.
2527 */
2528 if (arc_meta_max < aggsum_upper_bound(&arc_meta_used))
2529 arc_meta_max = aggsum_upper_bound(&arc_meta_used);
2530 aggsum_add(&arc_meta_used, -space);
2531 }
2532
2533 ASSERT(aggsum_compare(&arc_size, space) >= 0);
2534 aggsum_add(&arc_size, -space);
2535 }
2536
2537 /*
2538 * Given a hdr and a buf, returns whether that buf can share its b_data buffer
2539 * with the hdr's b_pabd.
2540 */
2541 static boolean_t
2542 arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2543 {
2544 /*
2545 * The criteria for sharing a hdr's data are:
2546 * 1. the buffer is not encrypted
2547 * 2. the hdr's compression matches the buf's compression
2548 * 3. the hdr doesn't need to be byteswapped
2549 * 4. the hdr isn't already being shared
2550 * 5. the buf is either compressed or it is the last buf in the hdr list
2551 *
2552 * Criterion #5 maintains the invariant that shared uncompressed
2553 * bufs must be the final buf in the hdr's b_buf list. Reading this, you
2554 * might ask, "if a compressed buf is allocated first, won't that be the
2555 * last thing in the list?", but in that case it's impossible to create
2556 * a shared uncompressed buf anyway (because the hdr must be compressed
2557 * to have the compressed buf). You might also think that #3 is
2558 * sufficient to make this guarantee, however it's possible
2559 * (specifically in the rare L2ARC write race mentioned in
2560 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that
2561 * is sharable, but wasn't at the time of its allocation. Rather than
2562 * allow a new shared uncompressed buf to be created and then shuffle
2563 * the list around to make it the last element, this simply disallows
2564 * sharing if the new buf isn't the first to be added.
2565 */
2566 ASSERT3P(buf->b_hdr, ==, hdr);
2567 boolean_t hdr_compressed = arc_hdr_get_compress(hdr) !=
2568 ZIO_COMPRESS_OFF;
2569 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
2570 return (!ARC_BUF_ENCRYPTED(buf) &&
2571 buf_compressed == hdr_compressed &&
2572 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
2573 !HDR_SHARED_DATA(hdr) &&
2574 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
2575 }
2576
2577 /*
2578 * Allocate a buf for this hdr. If you care about the data that's in the hdr,
2579 * or if you want a compressed buffer, pass those flags in. Returns 0 if the
2580 * copy was made successfully, or an error code otherwise.
2581 */
2582 static int
2583 arc_buf_alloc_impl(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb,
2584 void *tag, boolean_t encrypted, boolean_t compressed, boolean_t noauth,
2585 boolean_t fill, arc_buf_t **ret)
2586 {
2587 arc_buf_t *buf;
2588 arc_fill_flags_t flags = ARC_FILL_LOCKED;
2589
2590 ASSERT(HDR_HAS_L1HDR(hdr));
2591 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2592 VERIFY(hdr->b_type == ARC_BUFC_DATA ||
2593 hdr->b_type == ARC_BUFC_METADATA);
2594 ASSERT3P(ret, !=, NULL);
2595 ASSERT3P(*ret, ==, NULL);
2596 IMPLY(encrypted, compressed);
2597
2598 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2599 buf->b_hdr = hdr;
2600 buf->b_data = NULL;
2601 buf->b_next = hdr->b_l1hdr.b_buf;
2602 buf->b_flags = 0;
2603
2604 add_reference(hdr, tag);
2605
2606 /*
2607 * We're about to change the hdr's b_flags. We must either
2608 * hold the hash_lock or be undiscoverable.
2609 */
2610 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2611
2612 /*
2613 * Only honor requests for compressed bufs if the hdr is actually
2614 * compressed. This must be overriden if the buffer is encrypted since
2615 * encrypted buffers cannot be decompressed.
2616 */
2617 if (encrypted) {
2618 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2619 buf->b_flags |= ARC_BUF_FLAG_ENCRYPTED;
2620 flags |= ARC_FILL_COMPRESSED | ARC_FILL_ENCRYPTED;
2621 } else if (compressed &&
2622 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
2623 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2624 flags |= ARC_FILL_COMPRESSED;
2625 }
2626
2627 if (noauth) {
2628 ASSERT0(encrypted);
2629 flags |= ARC_FILL_NOAUTH;
2630 }
2631
2632 /*
2633 * If the hdr's data can be shared then we share the data buffer and
2634 * set the appropriate bit in the hdr's b_flags to indicate the hdr is
2635 * allocate a new buffer to store the buf's data.
2636 *
2637 * There are two additional restrictions here because we're sharing
2638 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
2639 * actively involved in an L2ARC write, because if this buf is used by
2640 * an arc_write() then the hdr's data buffer will be released when the
2641 * write completes, even though the L2ARC write might still be using it.
2642 * Second, the hdr's ABD must be linear so that the buf's user doesn't
2643 * need to be ABD-aware.
2644 */
2645 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) &&
2646 hdr->b_l1hdr.b_pabd != NULL && abd_is_linear(hdr->b_l1hdr.b_pabd);
2647
2648 /* Set up b_data and sharing */
2649 if (can_share) {
2650 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
2651 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2652 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2653 } else {
2654 buf->b_data =
2655 arc_get_data_buf(hdr, arc_buf_size(buf), buf);
2656 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2657 }
2658 VERIFY3P(buf->b_data, !=, NULL);
2659
2660 hdr->b_l1hdr.b_buf = buf;
2661 hdr->b_l1hdr.b_bufcnt += 1;
2662 if (encrypted)
2663 hdr->b_crypt_hdr.b_ebufcnt += 1;
2664
2665 /*
2666 * If the user wants the data from the hdr, we need to either copy or
2667 * decompress the data.
2668 */
2669 if (fill) {
2670 ASSERT3P(zb, !=, NULL);
2671 return (arc_buf_fill(buf, spa, zb, flags));
2672 }
2673
2674 return (0);
2675 }
2676
2677 static char *arc_onloan_tag = "onloan";
2678
2679 static inline void
2680 arc_loaned_bytes_update(int64_t delta)
2681 {
2682 atomic_add_64(&arc_loaned_bytes, delta);
2683
2684 /* assert that it did not wrap around */
2685 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
2686 }
2687
2688 /*
2689 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
2690 * flight data by arc_tempreserve_space() until they are "returned". Loaned
2691 * buffers must be returned to the arc before they can be used by the DMU or
2692 * freed.
2693 */
2694 arc_buf_t *
2695 arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
2696 {
2697 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
2698 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
2699
2700 arc_loaned_bytes_update(arc_buf_size(buf));
2701
2702 return (buf);
2703 }
2704
2705 arc_buf_t *
2706 arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
2707 enum zio_compress compression_type)
2708 {
2709 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
2710 psize, lsize, compression_type);
2711
2712 arc_loaned_bytes_update(arc_buf_size(buf));
2713
2714 return (buf);
2715 }
2716
2717 arc_buf_t *
2718 arc_loan_raw_buf(spa_t *spa, uint64_t dsobj, boolean_t byteorder,
2719 const uint8_t *salt, const uint8_t *iv, const uint8_t *mac,
2720 dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
2721 enum zio_compress compression_type)
2722 {
2723 arc_buf_t *buf = arc_alloc_raw_buf(spa, arc_onloan_tag, dsobj,
2724 byteorder, salt, iv, mac, ot, psize, lsize, compression_type);
2725
2726 atomic_add_64(&arc_loaned_bytes, psize);
2727 return (buf);
2728 }
2729
2730 /*
2731 * Performance tuning of L2ARC persistence:
2732 *
2733 * l2arc_rebuild_enabled : A ZFS module parameter that controls whether adding
2734 * an L2ARC device (either at pool import or later) will attempt
2735 * to rebuild L2ARC buffer contents.
2736 * l2arc_rebuild_blocks_min_l2size : A ZFS module parameter that controls
2737 * whether log blocks are written to the L2ARC device. If the L2ARC
2738 * device is less than 1GB, the amount of data l2arc_evict()
2739 * evicts is significant compared to the amount of restored L2ARC
2740 * data. In this case do not write log blocks in L2ARC in order
2741 * not to waste space.
2742 */
2743 int l2arc_rebuild_enabled = B_TRUE;
2744 unsigned long l2arc_rebuild_blocks_min_l2size = 1024 * 1024 * 1024;
2745
2746 /* L2ARC persistence rebuild control routines. */
2747 void l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen);
2748 static void l2arc_dev_rebuild_start(l2arc_dev_t *dev);
2749 static int l2arc_rebuild(l2arc_dev_t *dev);
2750
2751 /* L2ARC persistence read I/O routines. */
2752 static int l2arc_dev_hdr_read(l2arc_dev_t *dev);
2753 static int l2arc_log_blk_read(l2arc_dev_t *dev,
2754 const l2arc_log_blkptr_t *this_lp, const l2arc_log_blkptr_t *next_lp,
2755 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb,
2756 zio_t *this_io, zio_t **next_io);
2757 static zio_t *l2arc_log_blk_fetch(vdev_t *vd,
2758 const l2arc_log_blkptr_t *lp, l2arc_log_blk_phys_t *lb);
2759 static void l2arc_log_blk_fetch_abort(zio_t *zio);
2760
2761 /* L2ARC persistence block restoration routines. */
2762 static void l2arc_log_blk_restore(l2arc_dev_t *dev,
2763 const l2arc_log_blk_phys_t *lb, uint64_t lb_asize);
2764 static void l2arc_hdr_restore(const l2arc_log_ent_phys_t *le,
2765 l2arc_dev_t *dev);
2766
2767 /* L2ARC persistence write I/O routines. */
2768 static void l2arc_dev_hdr_update(l2arc_dev_t *dev);
2769 static void l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio,
2770 l2arc_write_callback_t *cb);
2771
2772 /* L2ARC persistence auxilliary routines. */
2773 boolean_t l2arc_log_blkptr_valid(l2arc_dev_t *dev,
2774 const l2arc_log_blkptr_t *lbp);
2775 static boolean_t l2arc_log_blk_insert(l2arc_dev_t *dev,
2776 const arc_buf_hdr_t *ab);
2777 boolean_t l2arc_range_check_overlap(uint64_t bottom,
2778 uint64_t top, uint64_t check);
2779 static void l2arc_blk_fetch_done(zio_t *zio);
2780 static inline uint64_t
2781 l2arc_log_blk_overhead(uint64_t write_sz, l2arc_dev_t *dev);
2782
2783 /*
2784 * Return a loaned arc buffer to the arc.
2785 */
2786 void
2787 arc_return_buf(arc_buf_t *buf, void *tag)
2788 {
2789 arc_buf_hdr_t *hdr = buf->b_hdr;
2790
2791 ASSERT3P(buf->b_data, !=, NULL);
2792 ASSERT(HDR_HAS_L1HDR(hdr));
2793 (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
2794 (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2795
2796 arc_loaned_bytes_update(-arc_buf_size(buf));
2797 }
2798
2799 /* Detach an arc_buf from a dbuf (tag) */
2800 void
2801 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
2802 {
2803 arc_buf_hdr_t *hdr = buf->b_hdr;
2804
2805 ASSERT3P(buf->b_data, !=, NULL);
2806 ASSERT(HDR_HAS_L1HDR(hdr));
2807 (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2808 (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
2809
2810 arc_loaned_bytes_update(arc_buf_size(buf));
2811 }
2812
2813 static void
2814 l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
2815 {
2816 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
2817
2818 df->l2df_abd = abd;
2819 df->l2df_size = size;
2820 df->l2df_type = type;
2821 mutex_enter(&l2arc_free_on_write_mtx);
2822 list_insert_head(l2arc_free_on_write, df);
2823 mutex_exit(&l2arc_free_on_write_mtx);
2824 }
2825
2826 static void
2827 arc_hdr_free_on_write(arc_buf_hdr_t *hdr, boolean_t free_rdata)
2828 {
2829 arc_state_t *state = hdr->b_l1hdr.b_state;
2830 arc_buf_contents_t type = arc_buf_type(hdr);
2831 uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr);
2832
2833 /* protected by hash lock, if in the hash table */
2834 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
2835 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2836 ASSERT(state != arc_anon && state != arc_l2c_only);
2837
2838 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2839 size, hdr);
2840 }
2841 (void) zfs_refcount_remove_many(&state->arcs_size, size, hdr);
2842 if (type == ARC_BUFC_METADATA) {
2843 arc_space_return(size, ARC_SPACE_META);
2844 } else {
2845 ASSERT(type == ARC_BUFC_DATA);
2846 arc_space_return(size, ARC_SPACE_DATA);
2847 }
2848
2849 if (free_rdata) {
2850 l2arc_free_abd_on_write(hdr->b_crypt_hdr.b_rabd, size, type);
2851 } else {
2852 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
2853 }
2854 }
2855
2856 /*
2857 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the
2858 * data buffer, we transfer the refcount ownership to the hdr and update
2859 * the appropriate kstats.
2860 */
2861 static void
2862 arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2863 {
2864 /* LINTED */
2865 arc_state_t *state = hdr->b_l1hdr.b_state;
2866
2867 ASSERT(arc_can_share(hdr, buf));
2868 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2869 ASSERT(!ARC_BUF_ENCRYPTED(buf));
2870 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2871
2872 /*
2873 * Start sharing the data buffer. We transfer the
2874 * refcount ownership to the hdr since it always owns
2875 * the refcount whenever an arc_buf_t is shared.
2876 */
2877 zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size,
2878 arc_hdr_size(hdr), buf, hdr);
2879 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
2880 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
2881 HDR_ISTYPE_METADATA(hdr));
2882 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2883 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2884
2885 /*
2886 * Since we've transferred ownership to the hdr we need
2887 * to increment its compressed and uncompressed kstats and
2888 * decrement the overhead size.
2889 */
2890 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
2891 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
2892 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
2893 }
2894
2895 static void
2896 arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2897 {
2898 /* LINTED */
2899 arc_state_t *state = hdr->b_l1hdr.b_state;
2900
2901 ASSERT(arc_buf_is_shared(buf));
2902 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2903 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2904
2905 /*
2906 * We are no longer sharing this buffer so we need
2907 * to transfer its ownership to the rightful owner.
2908 */
2909 zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size,
2910 arc_hdr_size(hdr), hdr, buf);
2911 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2912 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
2913 abd_put(hdr->b_l1hdr.b_pabd);
2914 hdr->b_l1hdr.b_pabd = NULL;
2915 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2916
2917 /*
2918 * Since the buffer is no longer shared between
2919 * the arc buf and the hdr, count it as overhead.
2920 */
2921 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
2922 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
2923 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2924 }
2925
2926 /*
2927 * Remove an arc_buf_t from the hdr's buf list and return the last
2928 * arc_buf_t on the list. If no buffers remain on the list then return
2929 * NULL.
2930 */
2931 static arc_buf_t *
2932 arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2933 {
2934 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
2935 arc_buf_t *lastbuf = NULL;
2936
2937 ASSERT(HDR_HAS_L1HDR(hdr));
2938 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2939
2940 /*
2941 * Remove the buf from the hdr list and locate the last
2942 * remaining buffer on the list.
2943 */
2944 while (*bufp != NULL) {
2945 if (*bufp == buf)
2946 *bufp = buf->b_next;
2947
2948 /*
2949 * If we've removed a buffer in the middle of
2950 * the list then update the lastbuf and update
2951 * bufp.
2952 */
2953 if (*bufp != NULL) {
2954 lastbuf = *bufp;
2955 bufp = &(*bufp)->b_next;
2956 }
2957 }
2958 buf->b_next = NULL;
2959 ASSERT3P(lastbuf, !=, buf);
2960 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
2961 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
2962 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
2963
2964 return (lastbuf);
2965 }
2966
2967 /*
2968 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
2969 * list and free it.
2970 */
2971 static void
2972 arc_buf_destroy_impl(arc_buf_t *buf)
2973 {
2974 arc_buf_hdr_t *hdr = buf->b_hdr;
2975
2976 /*
2977 * Free up the data associated with the buf but only if we're not
2978 * sharing this with the hdr. If we are sharing it with the hdr, the
2979 * hdr is responsible for doing the free.
2980 */
2981 if (buf->b_data != NULL) {
2982 /*
2983 * We're about to change the hdr's b_flags. We must either
2984 * hold the hash_lock or be undiscoverable.
2985 */
2986 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2987
2988 arc_cksum_verify(buf);
2989 arc_buf_unwatch(buf);
2990
2991 if (arc_buf_is_shared(buf)) {
2992 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2993 } else {
2994 uint64_t size = arc_buf_size(buf);
2995 arc_free_data_buf(hdr, buf->b_data, size, buf);
2996 ARCSTAT_INCR(arcstat_overhead_size, -size);
2997 }
2998 buf->b_data = NULL;
2999
3000 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3001 hdr->b_l1hdr.b_bufcnt -= 1;
3002
3003 if (ARC_BUF_ENCRYPTED(buf)) {
3004 hdr->b_crypt_hdr.b_ebufcnt -= 1;
3005
3006 /*
3007 * If we have no more encrypted buffers and we've
3008 * already gotten a copy of the decrypted data we can
3009 * free b_rabd to save some space.
3010 */
3011 if (hdr->b_crypt_hdr.b_ebufcnt == 0 &&
3012 HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd != NULL &&
3013 !HDR_IO_IN_PROGRESS(hdr)) {
3014 arc_hdr_free_pabd(hdr, B_TRUE);
3015 }
3016 }
3017 }
3018
3019 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
3020
3021 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
3022 /*
3023 * If the current arc_buf_t is sharing its data buffer with the
3024 * hdr, then reassign the hdr's b_pabd to share it with the new
3025 * buffer at the end of the list. The shared buffer is always
3026 * the last one on the hdr's buffer list.
3027 *
3028 * There is an equivalent case for compressed bufs, but since
3029 * they aren't guaranteed to be the last buf in the list and
3030 * that is an exceedingly rare case, we just allow that space be
3031 * wasted temporarily. We must also be careful not to share
3032 * encrypted buffers, since they cannot be shared.
3033 */
3034 if (lastbuf != NULL && !ARC_BUF_ENCRYPTED(lastbuf)) {
3035 /* Only one buf can be shared at once */
3036 VERIFY(!arc_buf_is_shared(lastbuf));
3037 /* hdr is uncompressed so can't have compressed buf */
3038 VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
3039
3040 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3041 arc_hdr_free_pabd(hdr, B_FALSE);
3042
3043 /*
3044 * We must setup a new shared block between the
3045 * last buffer and the hdr. The data would have
3046 * been allocated by the arc buf so we need to transfer
3047 * ownership to the hdr since it's now being shared.
3048 */
3049 arc_share_buf(hdr, lastbuf);
3050 }
3051 } else if (HDR_SHARED_DATA(hdr)) {
3052 /*
3053 * Uncompressed shared buffers are always at the end
3054 * of the list. Compressed buffers don't have the
3055 * same requirements. This makes it hard to
3056 * simply assert that the lastbuf is shared so
3057 * we rely on the hdr's compression flags to determine
3058 * if we have a compressed, shared buffer.
3059 */
3060 ASSERT3P(lastbuf, !=, NULL);
3061 ASSERT(arc_buf_is_shared(lastbuf) ||
3062 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
3063 }
3064
3065 /*
3066 * Free the checksum if we're removing the last uncompressed buf from
3067 * this hdr.
3068 */
3069 if (!arc_hdr_has_uncompressed_buf(hdr)) {
3070 arc_cksum_free(hdr);
3071 }
3072
3073 /* clean up the buf */
3074 buf->b_hdr = NULL;
3075 kmem_cache_free(buf_cache, buf);
3076 }
3077
3078 static void
3079 arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr, int alloc_flags)
3080 {
3081 uint64_t size;
3082 boolean_t alloc_rdata = ((alloc_flags & ARC_HDR_ALLOC_RDATA) != 0);
3083 boolean_t do_adapt = ((alloc_flags & ARC_HDR_DO_ADAPT) != 0);
3084
3085 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
3086 ASSERT(HDR_HAS_L1HDR(hdr));
3087 ASSERT(!HDR_SHARED_DATA(hdr) || alloc_rdata);
3088 IMPLY(alloc_rdata, HDR_PROTECTED(hdr));
3089
3090 if (alloc_rdata) {
3091 size = HDR_GET_PSIZE(hdr);
3092 ASSERT3P(hdr->b_crypt_hdr.b_rabd, ==, NULL);
3093 hdr->b_crypt_hdr.b_rabd = arc_get_data_abd(hdr, size, hdr,
3094 do_adapt);
3095 ASSERT3P(hdr->b_crypt_hdr.b_rabd, !=, NULL);
3096 } else {
3097 size = arc_hdr_size(hdr);
3098 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3099 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, size, hdr,
3100 do_adapt);
3101 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3102 }
3103
3104 ARCSTAT_INCR(arcstat_compressed_size, size);
3105 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3106 }
3107
3108 static void
3109 arc_hdr_free_pabd(arc_buf_hdr_t *hdr, boolean_t free_rdata)
3110 {
3111 uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr);
3112
3113 ASSERT(HDR_HAS_L1HDR(hdr));
3114 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
3115 IMPLY(free_rdata, HDR_HAS_RABD(hdr));
3116
3117
3118 /*
3119 * If the hdr is currently being written to the l2arc then
3120 * we defer freeing the data by adding it to the l2arc_free_on_write
3121 * list. The l2arc will free the data once it's finished
3122 * writing it to the l2arc device.
3123 */
3124 if (HDR_L2_WRITING(hdr)) {
3125 arc_hdr_free_on_write(hdr, free_rdata);
3126 ARCSTAT_BUMP(arcstat_l2_free_on_write);
3127 } else if (free_rdata) {
3128 arc_free_data_abd(hdr, hdr->b_crypt_hdr.b_rabd, size, hdr);
3129 } else {
3130 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
3131 size, hdr);
3132 }
3133
3134 if (free_rdata) {
3135 hdr->b_crypt_hdr.b_rabd = NULL;
3136 } else {
3137 hdr->b_l1hdr.b_pabd = NULL;
3138 }
3139
3140 if (hdr->b_l1hdr.b_pabd == NULL && !HDR_HAS_RABD(hdr))
3141 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3142
3143 ARCSTAT_INCR(arcstat_compressed_size, -size);
3144 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3145 }
3146
3147 static arc_buf_hdr_t *
3148 arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
3149 boolean_t protected, enum zio_compress compression_type,
3150 arc_buf_contents_t type, boolean_t alloc_rdata)
3151 {
3152 arc_buf_hdr_t *hdr;
3153 int flags = ARC_HDR_DO_ADAPT;
3154
3155 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
3156 if (protected) {
3157 hdr = kmem_cache_alloc(hdr_full_crypt_cache, KM_PUSHPAGE);
3158 } else {
3159 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
3160 }
3161 flags |= alloc_rdata ? ARC_HDR_ALLOC_RDATA : 0;
3162 ASSERT(HDR_EMPTY(hdr));
3163 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3164 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL);
3165 HDR_SET_PSIZE(hdr, psize);
3166 HDR_SET_LSIZE(hdr, lsize);
3167 hdr->b_spa = spa;
3168 hdr->b_type = type;
3169 hdr->b_flags = 0;
3170 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
3171 arc_hdr_set_compress(hdr, compression_type);
3172 if (protected)
3173 arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
3174
3175 hdr->b_l1hdr.b_state = arc_anon;
3176 hdr->b_l1hdr.b_arc_access = 0;
3177 hdr->b_l1hdr.b_bufcnt = 0;
3178 hdr->b_l1hdr.b_buf = NULL;
3179
3180 /*
3181 * Allocate the hdr's buffer. This will contain either
3182 * the compressed or uncompressed data depending on the block
3183 * it references and compressed arc enablement.
3184 */
3185 arc_hdr_alloc_pabd(hdr, flags);
3186 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3187
3188 return (hdr);
3189 }
3190
3191 /*
3192 * Transition between the two allocation states for the arc_buf_hdr struct.
3193 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
3194 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
3195 * version is used when a cache buffer is only in the L2ARC in order to reduce
3196 * memory usage.
3197 */
3198 static arc_buf_hdr_t *
3199 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
3200 {
3201 ASSERT(HDR_HAS_L2HDR(hdr));
3202
3203 arc_buf_hdr_t *nhdr;
3204 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3205
3206 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
3207 (old == hdr_l2only_cache && new == hdr_full_cache));
3208
3209 /*
3210 * if the caller wanted a new full header and the header is to be
3211 * encrypted we will actually allocate the header from the full crypt
3212 * cache instead. The same applies to freeing from the old cache.
3213 */
3214 if (HDR_PROTECTED(hdr) && new == hdr_full_cache)
3215 new = hdr_full_crypt_cache;
3216 if (HDR_PROTECTED(hdr) && old == hdr_full_cache)
3217 old = hdr_full_crypt_cache;
3218
3219 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
3220
3221 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
3222 buf_hash_remove(hdr);
3223
3224 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
3225
3226 if (new == hdr_full_cache || new == hdr_full_crypt_cache) {
3227 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3228 /*
3229 * arc_access and arc_change_state need to be aware that a
3230 * header has just come out of L2ARC, so we set its state to
3231 * l2c_only even though it's about to change.
3232 */
3233 nhdr->b_l1hdr.b_state = arc_l2c_only;
3234
3235 /* Verify previous threads set to NULL before freeing */
3236 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
3237 ASSERT(!HDR_HAS_RABD(hdr));
3238 } else {
3239 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3240 ASSERT0(hdr->b_l1hdr.b_bufcnt);
3241 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3242
3243 /*
3244 * If we've reached here, We must have been called from
3245 * arc_evict_hdr(), as such we should have already been
3246 * removed from any ghost list we were previously on
3247 * (which protects us from racing with arc_evict_state),
3248 * thus no locking is needed during this check.
3249 */
3250 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3251
3252 /*
3253 * A buffer must not be moved into the arc_l2c_only
3254 * state if it's not finished being written out to the
3255 * l2arc device. Otherwise, the b_l1hdr.b_pabd field
3256 * might try to be accessed, even though it was removed.
3257 */
3258 VERIFY(!HDR_L2_WRITING(hdr));
3259 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3260 ASSERT(!HDR_HAS_RABD(hdr));
3261
3262 #ifdef ZFS_DEBUG
3263 if (hdr->b_l1hdr.b_thawed != NULL) {
3264 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3265 hdr->b_l1hdr.b_thawed = NULL;
3266 }
3267 #endif
3268
3269 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3270 }
3271 /*
3272 * The header has been reallocated so we need to re-insert it into any
3273 * lists it was on.
3274 */
3275 (void) buf_hash_insert(nhdr, NULL);
3276
3277 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
3278
3279 mutex_enter(&dev->l2ad_mtx);
3280
3281 /*
3282 * We must place the realloc'ed header back into the list at
3283 * the same spot. Otherwise, if it's placed earlier in the list,
3284 * l2arc_write_buffers() could find it during the function's
3285 * write phase, and try to write it out to the l2arc.
3286 */
3287 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
3288 list_remove(&dev->l2ad_buflist, hdr);
3289
3290 mutex_exit(&dev->l2ad_mtx);
3291
3292 /*
3293 * Since we're using the pointer address as the tag when
3294 * incrementing and decrementing the l2ad_alloc refcount, we
3295 * must remove the old pointer (that we're about to destroy) and
3296 * add the new pointer to the refcount. Otherwise we'd remove
3297 * the wrong pointer address when calling arc_hdr_destroy() later.
3298 */
3299
3300 (void) zfs_refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr),
3301 hdr);
3302 (void) zfs_refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr),
3303 nhdr);
3304
3305 buf_discard_identity(hdr);
3306 kmem_cache_free(old, hdr);
3307
3308 return (nhdr);
3309 }
3310
3311 /*
3312 * This function allows an L1 header to be reallocated as a crypt
3313 * header and vice versa. If we are going to a crypt header, the
3314 * new fields will be zeroed out.
3315 */
3316 static arc_buf_hdr_t *
3317 arc_hdr_realloc_crypt(arc_buf_hdr_t *hdr, boolean_t need_crypt)
3318 {
3319 arc_buf_hdr_t *nhdr;
3320 arc_buf_t *buf;
3321 kmem_cache_t *ncache, *ocache;
3322
3323 ASSERT(HDR_HAS_L1HDR(hdr));
3324 ASSERT3U(!!HDR_PROTECTED(hdr), !=, need_crypt);
3325 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3326 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3327 ASSERT(!list_link_active(&hdr->b_l2hdr.b_l2node));
3328 ASSERT3P(hdr->b_hash_next, ==, NULL);
3329
3330 if (need_crypt) {
3331 ncache = hdr_full_crypt_cache;
3332 ocache = hdr_full_cache;
3333 } else {
3334 ncache = hdr_full_cache;
3335 ocache = hdr_full_crypt_cache;
3336 }
3337
3338 nhdr = kmem_cache_alloc(ncache, KM_PUSHPAGE);
3339
3340 /*
3341 * Copy all members that aren't locks or condvars to the new header.
3342 * No lists are pointing to us (as we asserted above), so we don't
3343 * need to worry about the list nodes.
3344 */
3345 nhdr->b_dva = hdr->b_dva;
3346 nhdr->b_birth = hdr->b_birth;
3347 nhdr->b_type = hdr->b_type;
3348 nhdr->b_flags = hdr->b_flags;
3349 nhdr->b_psize = hdr->b_psize;
3350 nhdr->b_lsize = hdr->b_lsize;
3351 nhdr->b_spa = hdr->b_spa;
3352 nhdr->b_l2hdr.b_dev = hdr->b_l2hdr.b_dev;
3353 nhdr->b_l2hdr.b_daddr = hdr->b_l2hdr.b_daddr;
3354 nhdr->b_l1hdr.b_freeze_cksum = hdr->b_l1hdr.b_freeze_cksum;
3355 nhdr->b_l1hdr.b_bufcnt = hdr->b_l1hdr.b_bufcnt;
3356 nhdr->b_l1hdr.b_byteswap = hdr->b_l1hdr.b_byteswap;
3357 nhdr->b_l1hdr.b_state = hdr->b_l1hdr.b_state;
3358 nhdr->b_l1hdr.b_arc_access = hdr->b_l1hdr.b_arc_access;
3359 nhdr->b_l1hdr.b_acb = hdr->b_l1hdr.b_acb;
3360 nhdr->b_l1hdr.b_pabd = hdr->b_l1hdr.b_pabd;
3361 #ifdef ZFS_DEBUG
3362 if (hdr->b_l1hdr.b_thawed != NULL) {
3363 nhdr->b_l1hdr.b_thawed = hdr->b_l1hdr.b_thawed;
3364 hdr->b_l1hdr.b_thawed = NULL;
3365 }
3366 #endif
3367
3368 /*
3369 * This refcount_add() exists only to ensure that the individual
3370 * arc buffers always point to a header that is referenced, avoiding
3371 * a small race condition that could trigger ASSERTs.
3372 */
3373 (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, FTAG);
3374 nhdr->b_l1hdr.b_buf = hdr->b_l1hdr.b_buf;
3375 for (buf = nhdr->b_l1hdr.b_buf; buf != NULL; buf = buf->b_next) {
3376 mutex_enter(&buf->b_evict_lock);
3377 buf->b_hdr = nhdr;
3378 mutex_exit(&buf->b_evict_lock);
3379 }
3380 zfs_refcount_transfer(&nhdr->b_l1hdr.b_refcnt, &hdr->b_l1hdr.b_refcnt);
3381 (void) zfs_refcount_remove(&nhdr->b_l1hdr.b_refcnt, FTAG);
3382 ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt));
3383
3384 if (need_crypt) {
3385 arc_hdr_set_flags(nhdr, ARC_FLAG_PROTECTED);
3386 } else {
3387 arc_hdr_clear_flags(nhdr, ARC_FLAG_PROTECTED);
3388 }
3389
3390 /* unset all members of the original hdr */
3391 bzero(&hdr->b_dva, sizeof (dva_t));
3392 hdr->b_birth = 0;
3393 hdr->b_type = ARC_BUFC_INVALID;
3394 hdr->b_flags = 0;
3395 hdr->b_psize = 0;
3396 hdr->b_lsize = 0;
3397 hdr->b_spa = 0;
3398 hdr->b_l2hdr.b_dev = NULL;
3399 hdr->b_l2hdr.b_daddr = 0;
3400 hdr->b_l1hdr.b_freeze_cksum = NULL;
3401 hdr->b_l1hdr.b_buf = NULL;
3402 hdr->b_l1hdr.b_bufcnt = 0;
3403 hdr->b_l1hdr.b_byteswap = 0;
3404 hdr->b_l1hdr.b_state = NULL;
3405 hdr->b_l1hdr.b_arc_access = 0;
3406 hdr->b_l1hdr.b_acb = NULL;
3407 hdr->b_l1hdr.b_pabd = NULL;
3408
3409 if (ocache == hdr_full_crypt_cache) {
3410 ASSERT(!HDR_HAS_RABD(hdr));
3411 hdr->b_crypt_hdr.b_ot = DMU_OT_NONE;
3412 hdr->b_crypt_hdr.b_ebufcnt = 0;
3413 hdr->b_crypt_hdr.b_dsobj = 0;
3414 bzero(hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3415 bzero(hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3416 bzero(hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3417 }
3418
3419 buf_discard_identity(hdr);
3420 kmem_cache_free(ocache, hdr);
3421
3422 return (nhdr);
3423 }
3424
3425 /*
3426 * This function is used by the send / receive code to convert a newly
3427 * allocated arc_buf_t to one that is suitable for a raw encrypted write. It
3428 * is also used to allow the root objset block to be uupdated without altering
3429 * its embedded MACs. Both block types will always be uncompressed so we do not
3430 * have to worry about compression type or psize.
3431 */
3432 void
3433 arc_convert_to_raw(arc_buf_t *buf, uint64_t dsobj, boolean_t byteorder,
3434 dmu_object_type_t ot, const uint8_t *salt, const uint8_t *iv,
3435 const uint8_t *mac)
3436 {
3437 arc_buf_hdr_t *hdr = buf->b_hdr;
3438
3439 ASSERT(ot == DMU_OT_DNODE || ot == DMU_OT_OBJSET);
3440 ASSERT(HDR_HAS_L1HDR(hdr));
3441 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3442
3443 buf->b_flags |= (ARC_BUF_FLAG_COMPRESSED | ARC_BUF_FLAG_ENCRYPTED);
3444 if (!HDR_PROTECTED(hdr))
3445 hdr = arc_hdr_realloc_crypt(hdr, B_TRUE);
3446 hdr->b_crypt_hdr.b_dsobj = dsobj;
3447 hdr->b_crypt_hdr.b_ot = ot;
3448 hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ?
3449 DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot);
3450 if (!arc_hdr_has_uncompressed_buf(hdr))
3451 arc_cksum_free(hdr);
3452
3453 if (salt != NULL)
3454 bcopy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3455 if (iv != NULL)
3456 bcopy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3457 if (mac != NULL)
3458 bcopy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3459 }
3460
3461 /*
3462 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
3463 * The buf is returned thawed since we expect the consumer to modify it.
3464 */
3465 arc_buf_t *
3466 arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
3467 {
3468 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
3469 B_FALSE, ZIO_COMPRESS_OFF, type, B_FALSE);
3470
3471 arc_buf_t *buf = NULL;
3472 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE, B_FALSE,
3473 B_FALSE, B_FALSE, &buf));
3474 arc_buf_thaw(buf);
3475
3476 return (buf);
3477 }
3478
3479 /*
3480 * Allocates an ARC buf header that's in an evicted & L2-cached state.
3481 * This is used during l2arc reconstruction to make empty ARC buffers
3482 * which circumvent the regular disk->arc->l2arc path and instead come
3483 * into being in the reverse order, i.e. l2arc->arc.
3484 */
3485 arc_buf_hdr_t *
3486 arc_buf_alloc_l2only(size_t size, arc_buf_contents_t type, l2arc_dev_t *dev,
3487 dva_t dva, uint64_t daddr, int32_t psize, uint64_t birth,
3488 enum zio_compress compress, boolean_t protected,
3489 boolean_t prefetch, arc_state_type_t arcs_state)
3490 {
3491 arc_buf_hdr_t *hdr;
3492
3493 ASSERT(size != 0);
3494 hdr = kmem_cache_alloc(hdr_l2only_cache, KM_SLEEP);
3495 hdr->b_birth = birth;
3496 hdr->b_type = type;
3497 hdr->b_flags = 0;
3498 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L2HDR);
3499 HDR_SET_LSIZE(hdr, size);
3500 HDR_SET_PSIZE(hdr, psize);
3501 arc_hdr_set_compress(hdr, compress);
3502 if (protected)
3503 arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
3504 if (prefetch)
3505 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
3506 hdr->b_spa = spa_load_guid(dev->l2ad_vdev->vdev_spa);
3507
3508 hdr->b_dva = dva;
3509
3510 hdr->b_l2hdr.b_dev = dev;
3511 hdr->b_l2hdr.b_daddr = daddr;
3512 hdr->b_l2hdr.b_arcs_state = arcs_state;
3513
3514 return (hdr);
3515 }
3516
3517 /*
3518 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
3519 * for bufs containing metadata.
3520 */
3521 arc_buf_t *
3522 arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
3523 enum zio_compress compression_type)
3524 {
3525 ASSERT3U(lsize, >, 0);
3526 ASSERT3U(lsize, >=, psize);
3527 ASSERT3U(compression_type, >, ZIO_COMPRESS_OFF);
3528 ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS);
3529
3530 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
3531 B_FALSE, compression_type, ARC_BUFC_DATA, B_FALSE);
3532
3533 arc_buf_t *buf = NULL;
3534 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE,
3535 B_TRUE, B_FALSE, B_FALSE, &buf));
3536 arc_buf_thaw(buf);
3537 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3538
3539 if (!arc_buf_is_shared(buf)) {
3540 /*
3541 * To ensure that the hdr has the correct data in it if we call
3542 * arc_untransform() on this buf before it's been written to
3543 * disk, it's easiest if we just set up sharing between the
3544 * buf and the hdr.
3545 */
3546 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd));
3547 arc_hdr_free_pabd(hdr, B_FALSE);
3548 arc_share_buf(hdr, buf);
3549 }
3550
3551 return (buf);
3552 }
3553
3554 arc_buf_t *
3555 arc_alloc_raw_buf(spa_t *spa, void *tag, uint64_t dsobj, boolean_t byteorder,
3556 const uint8_t *salt, const uint8_t *iv, const uint8_t *mac,
3557 dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
3558 enum zio_compress compression_type)
3559 {
3560 arc_buf_hdr_t *hdr;
3561 arc_buf_t *buf;
3562 arc_buf_contents_t type = DMU_OT_IS_METADATA(ot) ?
3563 ARC_BUFC_METADATA : ARC_BUFC_DATA;
3564
3565 ASSERT3U(lsize, >, 0);
3566 ASSERT3U(lsize, >=, psize);
3567 ASSERT3U(compression_type, >=, ZIO_COMPRESS_OFF);
3568 ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS);
3569
3570 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, B_TRUE,
3571 compression_type, type, B_TRUE);
3572
3573 hdr->b_crypt_hdr.b_dsobj = dsobj;
3574 hdr->b_crypt_hdr.b_ot = ot;
3575 hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ?
3576 DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot);
3577 bcopy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3578 bcopy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3579 bcopy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3580
3581 /*
3582 * This buffer will be considered encrypted even if the ot is not an
3583 * encrypted type. It will become authenticated instead in
3584 * arc_write_ready().
3585 */
3586 buf = NULL;
3587 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_TRUE, B_TRUE,
3588 B_FALSE, B_FALSE, &buf));
3589 arc_buf_thaw(buf);
3590 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3591
3592 return (buf);
3593 }
3594
3595 static void
3596 l2arc_hdr_arcstats_update(arc_buf_hdr_t *hdr, boolean_t incr,
3597 boolean_t state_only)
3598 {
3599 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3600 l2arc_dev_t *dev = l2hdr->b_dev;
3601 uint64_t lsize = HDR_GET_LSIZE(hdr);
3602 uint64_t psize = HDR_GET_PSIZE(hdr);
3603 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
3604 arc_buf_contents_t type = hdr->b_type;
3605 int64_t lsize_s;
3606 int64_t psize_s;
3607 int64_t asize_s;
3608
3609 if (incr) {
3610 lsize_s = lsize;
3611 psize_s = psize;
3612 asize_s = asize;
3613 } else {
3614 lsize_s = -lsize;
3615 psize_s = -psize;
3616 asize_s = -asize;
3617 }
3618
3619 /* If the buffer is a prefetch, count it as such. */
3620 if (HDR_PREFETCH(hdr)) {
3621 ARCSTAT_INCR(arcstat_l2_prefetch_asize, asize_s);
3622 } else {
3623 /*
3624 * We use the value stored in the L2 header upon initial
3625 * caching in L2ARC. This value will be updated in case
3626 * an MRU/MRU_ghost buffer transitions to MFU but the L2ARC
3627 * metadata (log entry) cannot currently be updated. Having
3628 * the ARC state in the L2 header solves the problem of a
3629 * possibly absent L1 header (apparent in buffers restored
3630 * from persistent L2ARC).
3631 */
3632 switch (hdr->b_l2hdr.b_arcs_state) {
3633 case ARC_STATE_MRU_GHOST:
3634 case ARC_STATE_MRU:
3635 ARCSTAT_INCR(arcstat_l2_mru_asize, asize_s);
3636 break;
3637 case ARC_STATE_MFU_GHOST:
3638 case ARC_STATE_MFU:
3639 ARCSTAT_INCR(arcstat_l2_mfu_asize, asize_s);
3640 break;
3641 default:
3642 break;
3643 }
3644 }
3645
3646 if (state_only)
3647 return;
3648
3649 ARCSTAT_INCR(arcstat_l2_psize, psize_s);
3650 ARCSTAT_INCR(arcstat_l2_lsize, lsize_s);
3651
3652 switch (type) {
3653 case ARC_BUFC_DATA:
3654 ARCSTAT_INCR(arcstat_l2_bufc_data_asize, asize_s);
3655 break;
3656 case ARC_BUFC_METADATA:
3657 ARCSTAT_INCR(arcstat_l2_bufc_metadata_asize, asize_s);
3658 break;
3659 default:
3660 break;
3661 }
3662 }
3663
3664
3665 static void
3666 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
3667 {
3668 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3669 l2arc_dev_t *dev = l2hdr->b_dev;
3670 uint64_t psize = HDR_GET_PSIZE(hdr);
3671 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
3672
3673 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
3674 ASSERT(HDR_HAS_L2HDR(hdr));
3675
3676 list_remove(&dev->l2ad_buflist, hdr);
3677
3678 l2arc_hdr_arcstats_decrement(hdr);
3679 vdev_space_update(dev->l2ad_vdev, -asize, 0, 0);
3680
3681 (void) zfs_refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr),
3682 hdr);
3683 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
3684 }
3685
3686 static void
3687 arc_hdr_destroy(arc_buf_hdr_t *hdr)
3688 {
3689 if (HDR_HAS_L1HDR(hdr)) {
3690 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
3691 hdr->b_l1hdr.b_bufcnt > 0);
3692 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3693 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3694 }
3695 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3696 ASSERT(!HDR_IN_HASH_TABLE(hdr));
3697
3698 if (HDR_HAS_L2HDR(hdr)) {
3699 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3700 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
3701
3702 if (!buflist_held)
3703 mutex_enter(&dev->l2ad_mtx);
3704
3705 /*
3706 * Even though we checked this conditional above, we
3707 * need to check this again now that we have the
3708 * l2ad_mtx. This is because we could be racing with
3709 * another thread calling l2arc_evict() which might have
3710 * destroyed this header's L2 portion as we were waiting
3711 * to acquire the l2ad_mtx. If that happens, we don't
3712 * want to re-destroy the header's L2 portion.
3713 */
3714 if (HDR_HAS_L2HDR(hdr))
3715 arc_hdr_l2hdr_destroy(hdr);
3716
3717 if (!buflist_held)
3718 mutex_exit(&dev->l2ad_mtx);
3719 }
3720
3721 /*
3722 * The header's identity can only be safely discarded once it is no
3723 * longer discoverable. This requires removing it from the hash table
3724 * and the l2arc header list. After this point the hash lock can not
3725 * be used to protect the header.
3726 */
3727 if (!HDR_EMPTY(hdr))
3728 buf_discard_identity(hdr);
3729
3730 if (HDR_HAS_L1HDR(hdr)) {
3731 arc_cksum_free(hdr);
3732
3733 while (hdr->b_l1hdr.b_buf != NULL)
3734 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
3735
3736 #ifdef ZFS_DEBUG
3737 if (hdr->b_l1hdr.b_thawed != NULL) {
3738 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3739 hdr->b_l1hdr.b_thawed = NULL;
3740 }
3741 #endif
3742
3743 if (hdr->b_l1hdr.b_pabd != NULL)
3744 arc_hdr_free_pabd(hdr, B_FALSE);
3745
3746 if (HDR_HAS_RABD(hdr))
3747 arc_hdr_free_pabd(hdr, B_TRUE);
3748 }
3749
3750 ASSERT3P(hdr->b_hash_next, ==, NULL);
3751 if (HDR_HAS_L1HDR(hdr)) {
3752 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3753 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
3754
3755 if (!HDR_PROTECTED(hdr)) {
3756 kmem_cache_free(hdr_full_cache, hdr);
3757 } else {
3758 kmem_cache_free(hdr_full_crypt_cache, hdr);
3759 }
3760 } else {
3761 kmem_cache_free(hdr_l2only_cache, hdr);
3762 }
3763 }
3764
3765 void
3766 arc_buf_destroy(arc_buf_t *buf, void* tag)
3767 {
3768 arc_buf_hdr_t *hdr = buf->b_hdr;
3769
3770 if (hdr->b_l1hdr.b_state == arc_anon) {
3771 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
3772 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3773 VERIFY0(remove_reference(hdr, NULL, tag));
3774 arc_hdr_destroy(hdr);
3775 return;
3776 }
3777
3778 kmutex_t *hash_lock = HDR_LOCK(hdr);
3779 mutex_enter(hash_lock);
3780
3781 ASSERT3P(hdr, ==, buf->b_hdr);
3782 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3783 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3784 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
3785 ASSERT3P(buf->b_data, !=, NULL);
3786
3787 (void) remove_reference(hdr, hash_lock, tag);
3788 arc_buf_destroy_impl(buf);
3789 mutex_exit(hash_lock);
3790 }
3791
3792 /*
3793 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
3794 * state of the header is dependent on its state prior to entering this
3795 * function. The following transitions are possible:
3796 *
3797 * - arc_mru -> arc_mru_ghost
3798 * - arc_mfu -> arc_mfu_ghost
3799 * - arc_mru_ghost -> arc_l2c_only
3800 * - arc_mru_ghost -> deleted
3801 * - arc_mfu_ghost -> arc_l2c_only
3802 * - arc_mfu_ghost -> deleted
3803 */
3804 static int64_t
3805 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3806 {
3807 arc_state_t *evicted_state, *state;
3808 int64_t bytes_evicted = 0;
3809 int min_lifetime = HDR_PRESCIENT_PREFETCH(hdr) ?
3810 zfs_arc_min_prescient_prefetch_ms : zfs_arc_min_prefetch_ms;
3811
3812 ASSERT(MUTEX_HELD(hash_lock));
3813 ASSERT(HDR_HAS_L1HDR(hdr));
3814
3815 state = hdr->b_l1hdr.b_state;
3816 if (GHOST_STATE(state)) {
3817 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3818 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3819
3820 /*
3821 * l2arc_write_buffers() relies on a header's L1 portion
3822 * (i.e. its b_pabd field) during its write phase.
3823 * Thus, we cannot push a header onto the arc_l2c_only
3824 * state (removing its L1 piece) until the header is
3825 * done being written to the l2arc.
3826 */
3827 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
3828 ARCSTAT_BUMP(arcstat_evict_l2_skip);
3829 return (bytes_evicted);
3830 }
3831
3832 ARCSTAT_BUMP(arcstat_deleted);
3833 bytes_evicted += HDR_GET_LSIZE(hdr);
3834
3835 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
3836
3837 if (HDR_HAS_L2HDR(hdr)) {
3838 ASSERT(hdr->b_l1hdr.b_pabd == NULL);
3839 ASSERT(!HDR_HAS_RABD(hdr));
3840 /*
3841 * This buffer is cached on the 2nd Level ARC;
3842 * don't destroy the header.
3843 */
3844 arc_change_state(arc_l2c_only, hdr, hash_lock);
3845 /*
3846 * dropping from L1+L2 cached to L2-only,
3847 * realloc to remove the L1 header.
3848 */
3849 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
3850 hdr_l2only_cache);
3851 } else {
3852 arc_change_state(arc_anon, hdr, hash_lock);
3853 arc_hdr_destroy(hdr);
3854 }
3855 return (bytes_evicted);
3856 }
3857
3858 ASSERT(state == arc_mru || state == arc_mfu);
3859 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3860
3861 /* prefetch buffers have a minimum lifespan */
3862 if (HDR_IO_IN_PROGRESS(hdr) ||
3863 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
3864 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < min_lifetime * hz)) {
3865 ARCSTAT_BUMP(arcstat_evict_skip);
3866 return (bytes_evicted);
3867 }
3868
3869 ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt));
3870 while (hdr->b_l1hdr.b_buf) {
3871 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
3872 if (!mutex_tryenter(&buf->b_evict_lock)) {
3873 ARCSTAT_BUMP(arcstat_mutex_miss);
3874 break;
3875 }
3876 if (buf->b_data != NULL)
3877 bytes_evicted += HDR_GET_LSIZE(hdr);
3878 mutex_exit(&buf->b_evict_lock);
3879 arc_buf_destroy_impl(buf);
3880 }
3881
3882 if (HDR_HAS_L2HDR(hdr)) {
3883 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
3884 } else {
3885 if (l2arc_write_eligible(hdr->b_spa, hdr)) {
3886 ARCSTAT_INCR(arcstat_evict_l2_eligible,
3887 HDR_GET_LSIZE(hdr));
3888
3889 switch (state->arcs_state) {
3890 case ARC_STATE_MRU:
3891 ARCSTAT_INCR(
3892 arcstat_evict_l2_eligible_mru,
3893 HDR_GET_LSIZE(hdr));
3894 break;
3895 case ARC_STATE_MFU:
3896 ARCSTAT_INCR(
3897 arcstat_evict_l2_eligible_mfu,
3898 HDR_GET_LSIZE(hdr));
3899 break;
3900 default:
3901 break;
3902 }
3903 } else {
3904 ARCSTAT_INCR(arcstat_evict_l2_ineligible,
3905 HDR_GET_LSIZE(hdr));
3906 }
3907 }
3908
3909 if (hdr->b_l1hdr.b_bufcnt == 0) {
3910 arc_cksum_free(hdr);
3911
3912 bytes_evicted += arc_hdr_size(hdr);
3913
3914 /*
3915 * If this hdr is being evicted and has a compressed
3916 * buffer then we discard it here before we change states.
3917 * This ensures that the accounting is updated correctly
3918 * in arc_free_data_impl().
3919 */
3920 if (hdr->b_l1hdr.b_pabd != NULL)
3921 arc_hdr_free_pabd(hdr, B_FALSE);
3922
3923 if (HDR_HAS_RABD(hdr))
3924 arc_hdr_free_pabd(hdr, B_TRUE);
3925
3926 arc_change_state(evicted_state, hdr, hash_lock);
3927 ASSERT(HDR_IN_HASH_TABLE(hdr));
3928 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
3929 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
3930 }
3931
3932 return (bytes_evicted);
3933 }
3934
3935 static uint64_t
3936 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
3937 uint64_t spa, int64_t bytes)
3938 {
3939 multilist_sublist_t *mls;
3940 uint64_t bytes_evicted = 0;
3941 arc_buf_hdr_t *hdr;
3942 kmutex_t *hash_lock;
3943 int evict_count = 0;
3944
3945 ASSERT3P(marker, !=, NULL);
3946 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3947
3948 mls = multilist_sublist_lock(ml, idx);
3949
3950 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
3951 hdr = multilist_sublist_prev(mls, marker)) {
3952 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
3953 (evict_count >= zfs_arc_evict_batch_limit))
3954 break;
3955
3956 /*
3957 * To keep our iteration location, move the marker
3958 * forward. Since we're not holding hdr's hash lock, we
3959 * must be very careful and not remove 'hdr' from the
3960 * sublist. Otherwise, other consumers might mistake the
3961 * 'hdr' as not being on a sublist when they call the
3962 * multilist_link_active() function (they all rely on
3963 * the hash lock protecting concurrent insertions and
3964 * removals). multilist_sublist_move_forward() was
3965 * specifically implemented to ensure this is the case
3966 * (only 'marker' will be removed and re-inserted).
3967 */
3968 multilist_sublist_move_forward(mls, marker);
3969
3970 /*
3971 * The only case where the b_spa field should ever be
3972 * zero, is the marker headers inserted by
3973 * arc_evict_state(). It's possible for multiple threads
3974 * to be calling arc_evict_state() concurrently (e.g.
3975 * dsl_pool_close() and zio_inject_fault()), so we must
3976 * skip any markers we see from these other threads.
3977 */
3978 if (hdr->b_spa == 0)
3979 continue;
3980
3981 /* we're only interested in evicting buffers of a certain spa */
3982 if (spa != 0 && hdr->b_spa != spa) {
3983 ARCSTAT_BUMP(arcstat_evict_skip);
3984 continue;
3985 }
3986
3987 hash_lock = HDR_LOCK(hdr);
3988
3989 /*
3990 * We aren't calling this function from any code path
3991 * that would already be holding a hash lock, so we're
3992 * asserting on this assumption to be defensive in case
3993 * this ever changes. Without this check, it would be
3994 * possible to incorrectly increment arcstat_mutex_miss
3995 * below (e.g. if the code changed such that we called
3996 * this function with a hash lock held).
3997 */
3998 ASSERT(!MUTEX_HELD(hash_lock));
3999
4000 if (mutex_tryenter(hash_lock)) {
4001 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
4002 mutex_exit(hash_lock);
4003
4004 bytes_evicted += evicted;
4005
4006 /*
4007 * If evicted is zero, arc_evict_hdr() must have
4008 * decided to skip this header, don't increment
4009 * evict_count in this case.
4010 */
4011 if (evicted != 0)
4012 evict_count++;
4013
4014 /*
4015 * If arc_size isn't overflowing, signal any
4016 * threads that might happen to be waiting.
4017 *
4018 * For each header evicted, we wake up a single
4019 * thread. If we used cv_broadcast, we could
4020 * wake up "too many" threads causing arc_size
4021 * to significantly overflow arc_c; since
4022 * arc_get_data_impl() doesn't check for overflow
4023 * when it's woken up (it doesn't because it's
4024 * possible for the ARC to be overflowing while
4025 * full of un-evictable buffers, and the
4026 * function should proceed in this case).
4027 *
4028 * If threads are left sleeping, due to not
4029 * using cv_broadcast here, they will be woken
4030 * up via cv_broadcast in arc_adjust_cb() just
4031 * before arc_adjust_zthr sleeps.
4032 */
4033 mutex_enter(&arc_adjust_lock);
4034 if (!arc_is_overflowing())
4035 cv_signal(&arc_adjust_waiters_cv);
4036 mutex_exit(&arc_adjust_lock);
4037 } else {
4038 ARCSTAT_BUMP(arcstat_mutex_miss);
4039 }
4040 }
4041
4042 multilist_sublist_unlock(mls);
4043
4044 return (bytes_evicted);
4045 }
4046
4047 /*
4048 * Evict buffers from the given arc state, until we've removed the
4049 * specified number of bytes. Move the removed buffers to the
4050 * appropriate evict state.
4051 *
4052 * This function makes a "best effort". It skips over any buffers
4053 * it can't get a hash_lock on, and so, may not catch all candidates.
4054 * It may also return without evicting as much space as requested.
4055 *
4056 * If bytes is specified using the special value ARC_EVICT_ALL, this
4057 * will evict all available (i.e. unlocked and evictable) buffers from
4058 * the given arc state; which is used by arc_flush().
4059 */
4060 static uint64_t
4061 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
4062 arc_buf_contents_t type)
4063 {
4064 uint64_t total_evicted = 0;
4065 multilist_t *ml = state->arcs_list[type];
4066 int num_sublists;
4067 arc_buf_hdr_t **markers;
4068
4069 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
4070
4071 num_sublists = multilist_get_num_sublists(ml);
4072
4073 /*
4074 * If we've tried to evict from each sublist, made some
4075 * progress, but still have not hit the target number of bytes
4076 * to evict, we want to keep trying. The markers allow us to
4077 * pick up where we left off for each individual sublist, rather
4078 * than starting from the tail each time.
4079 */
4080 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
4081 for (int i = 0; i < num_sublists; i++) {
4082 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
4083
4084 /*
4085 * A b_spa of 0 is used to indicate that this header is
4086 * a marker. This fact is used in arc_adjust_type() and
4087 * arc_evict_state_impl().
4088 */
4089 markers[i]->b_spa = 0;
4090
4091 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
4092 multilist_sublist_insert_tail(mls, markers[i]);
4093 multilist_sublist_unlock(mls);
4094 }
4095
4096 /*
4097 * While we haven't hit our target number of bytes to evict, or
4098 * we're evicting all available buffers.
4099 */
4100 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
4101 /*
4102 * Start eviction using a randomly selected sublist,
4103 * this is to try and evenly balance eviction across all
4104 * sublists. Always starting at the same sublist
4105 * (e.g. index 0) would cause evictions to favor certain
4106 * sublists over others.
4107 */
4108 int sublist_idx = multilist_get_random_index(ml);
4109 uint64_t scan_evicted = 0;
4110
4111 for (int i = 0; i < num_sublists; i++) {
4112 uint64_t bytes_remaining;
4113 uint64_t bytes_evicted;
4114
4115 if (bytes == ARC_EVICT_ALL)
4116 bytes_remaining = ARC_EVICT_ALL;
4117 else if (total_evicted < bytes)
4118 bytes_remaining = bytes - total_evicted;
4119 else
4120 break;
4121
4122 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
4123 markers[sublist_idx], spa, bytes_remaining);
4124
4125 scan_evicted += bytes_evicted;
4126 total_evicted += bytes_evicted;
4127
4128 /* we've reached the end, wrap to the beginning */
4129 if (++sublist_idx >= num_sublists)
4130 sublist_idx = 0;
4131 }
4132
4133 /*
4134 * If we didn't evict anything during this scan, we have
4135 * no reason to believe we'll evict more during another
4136 * scan, so break the loop.
4137 */
4138 if (scan_evicted == 0) {
4139 /* This isn't possible, let's make that obvious */
4140 ASSERT3S(bytes, !=, 0);
4141
4142 /*
4143 * When bytes is ARC_EVICT_ALL, the only way to
4144 * break the loop is when scan_evicted is zero.
4145 * In that case, we actually have evicted enough,
4146 * so we don't want to increment the kstat.
4147 */
4148 if (bytes != ARC_EVICT_ALL) {
4149 ASSERT3S(total_evicted, <, bytes);
4150 ARCSTAT_BUMP(arcstat_evict_not_enough);
4151 }
4152
4153 break;
4154 }
4155 }
4156
4157 for (int i = 0; i < num_sublists; i++) {
4158 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
4159 multilist_sublist_remove(mls, markers[i]);
4160 multilist_sublist_unlock(mls);
4161
4162 kmem_cache_free(hdr_full_cache, markers[i]);
4163 }
4164 kmem_free(markers, sizeof (*markers) * num_sublists);
4165
4166 return (total_evicted);
4167 }
4168
4169 /*
4170 * Flush all "evictable" data of the given type from the arc state
4171 * specified. This will not evict any "active" buffers (i.e. referenced).
4172 *
4173 * When 'retry' is set to B_FALSE, the function will make a single pass
4174 * over the state and evict any buffers that it can. Since it doesn't
4175 * continually retry the eviction, it might end up leaving some buffers
4176 * in the ARC due to lock misses.
4177 *
4178 * When 'retry' is set to B_TRUE, the function will continually retry the
4179 * eviction until *all* evictable buffers have been removed from the
4180 * state. As a result, if concurrent insertions into the state are
4181 * allowed (e.g. if the ARC isn't shutting down), this function might
4182 * wind up in an infinite loop, continually trying to evict buffers.
4183 */
4184 static uint64_t
4185 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
4186 boolean_t retry)
4187 {
4188 uint64_t evicted = 0;
4189
4190 while (zfs_refcount_count(&state->arcs_esize[type]) != 0) {
4191 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
4192
4193 if (!retry)
4194 break;
4195 }
4196
4197 return (evicted);
4198 }
4199
4200 /*
4201 * Evict the specified number of bytes from the state specified,
4202 * restricting eviction to the spa and type given. This function
4203 * prevents us from trying to evict more from a state's list than
4204 * is "evictable", and to skip evicting altogether when passed a
4205 * negative value for "bytes". In contrast, arc_evict_state() will
4206 * evict everything it can, when passed a negative value for "bytes".
4207 */
4208 static uint64_t
4209 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
4210 arc_buf_contents_t type)
4211 {
4212 int64_t delta;
4213
4214 if (bytes > 0 && zfs_refcount_count(&state->arcs_esize[type]) > 0) {
4215 delta = MIN(zfs_refcount_count(&state->arcs_esize[type]),
4216 bytes);
4217 return (arc_evict_state(state, spa, delta, type));
4218 }
4219
4220 return (0);
4221 }
4222
4223 /*
4224 * Evict metadata buffers from the cache, such that arc_meta_used is
4225 * capped by the arc_meta_limit tunable.
4226 */
4227 static uint64_t
4228 arc_adjust_meta(uint64_t meta_used)
4229 {
4230 uint64_t total_evicted = 0;
4231 int64_t target;
4232
4233 /*
4234 * If we're over the meta limit, we want to evict enough
4235 * metadata to get back under the meta limit. We don't want to
4236 * evict so much that we drop the MRU below arc_p, though. If
4237 * we're over the meta limit more than we're over arc_p, we
4238 * evict some from the MRU here, and some from the MFU below.
4239 */
4240 target = MIN((int64_t)(meta_used - arc_meta_limit),
4241 (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) +
4242 zfs_refcount_count(&arc_mru->arcs_size) - arc_p));
4243
4244 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4245
4246 /*
4247 * Similar to the above, we want to evict enough bytes to get us
4248 * below the meta limit, but not so much as to drop us below the
4249 * space allotted to the MFU (which is defined as arc_c - arc_p).
4250 */
4251 target = MIN((int64_t)(meta_used - arc_meta_limit),
4252 (int64_t)(zfs_refcount_count(&arc_mfu->arcs_size) -
4253 (arc_c - arc_p)));
4254
4255 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4256
4257 return (total_evicted);
4258 }
4259
4260 /*
4261 * Return the type of the oldest buffer in the given arc state
4262 *
4263 * This function will select a random sublist of type ARC_BUFC_DATA and
4264 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
4265 * is compared, and the type which contains the "older" buffer will be
4266 * returned.
4267 */
4268 static arc_buf_contents_t
4269 arc_adjust_type(arc_state_t *state)
4270 {
4271 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
4272 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
4273 int data_idx = multilist_get_random_index(data_ml);
4274 int meta_idx = multilist_get_random_index(meta_ml);
4275 multilist_sublist_t *data_mls;
4276 multilist_sublist_t *meta_mls;
4277 arc_buf_contents_t type;
4278 arc_buf_hdr_t *data_hdr;
4279 arc_buf_hdr_t *meta_hdr;
4280
4281 /*
4282 * We keep the sublist lock until we're finished, to prevent
4283 * the headers from being destroyed via arc_evict_state().
4284 */
4285 data_mls = multilist_sublist_lock(data_ml, data_idx);
4286 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
4287
4288 /*
4289 * These two loops are to ensure we skip any markers that
4290 * might be at the tail of the lists due to arc_evict_state().
4291 */
4292
4293 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
4294 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
4295 if (data_hdr->b_spa != 0)
4296 break;
4297 }
4298
4299 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
4300 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
4301 if (meta_hdr->b_spa != 0)
4302 break;
4303 }
4304
4305 if (data_hdr == NULL && meta_hdr == NULL) {
4306 type = ARC_BUFC_DATA;
4307 } else if (data_hdr == NULL) {
4308 ASSERT3P(meta_hdr, !=, NULL);
4309 type = ARC_BUFC_METADATA;
4310 } else if (meta_hdr == NULL) {
4311 ASSERT3P(data_hdr, !=, NULL);
4312 type = ARC_BUFC_DATA;
4313 } else {
4314 ASSERT3P(data_hdr, !=, NULL);
4315 ASSERT3P(meta_hdr, !=, NULL);
4316
4317 /* The headers can't be on the sublist without an L1 header */
4318 ASSERT(HDR_HAS_L1HDR(data_hdr));
4319 ASSERT(HDR_HAS_L1HDR(meta_hdr));
4320
4321 if (data_hdr->b_l1hdr.b_arc_access <
4322 meta_hdr->b_l1hdr.b_arc_access) {
4323 type = ARC_BUFC_DATA;
4324 } else {
4325 type = ARC_BUFC_METADATA;
4326 }
4327 }
4328
4329 multilist_sublist_unlock(meta_mls);
4330 multilist_sublist_unlock(data_mls);
4331
4332 return (type);
4333 }
4334
4335 /*
4336 * Evict buffers from the cache, such that arc_size is capped by arc_c.
4337 */
4338 static uint64_t
4339 arc_adjust(void)
4340 {
4341 uint64_t total_evicted = 0;
4342 uint64_t bytes;
4343 int64_t target;
4344 uint64_t asize = aggsum_value(&arc_size);
4345 uint64_t ameta = aggsum_value(&arc_meta_used);
4346
4347 /*
4348 * If we're over arc_meta_limit, we want to correct that before
4349 * potentially evicting data buffers below.
4350 */
4351 total_evicted += arc_adjust_meta(ameta);
4352
4353 /*
4354 * Adjust MRU size
4355 *
4356 * If we're over the target cache size, we want to evict enough
4357 * from the list to get back to our target size. We don't want
4358 * to evict too much from the MRU, such that it drops below
4359 * arc_p. So, if we're over our target cache size more than
4360 * the MRU is over arc_p, we'll evict enough to get back to
4361 * arc_p here, and then evict more from the MFU below.
4362 */
4363 target = MIN((int64_t)(asize - arc_c),
4364 (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) +
4365 zfs_refcount_count(&arc_mru->arcs_size) + ameta - arc_p));
4366
4367 /*
4368 * If we're below arc_meta_min, always prefer to evict data.
4369 * Otherwise, try to satisfy the requested number of bytes to
4370 * evict from the type which contains older buffers; in an
4371 * effort to keep newer buffers in the cache regardless of their
4372 * type. If we cannot satisfy the number of bytes from this
4373 * type, spill over into the next type.
4374 */
4375 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
4376 ameta > arc_meta_min) {
4377 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4378 total_evicted += bytes;
4379
4380 /*
4381 * If we couldn't evict our target number of bytes from
4382 * metadata, we try to get the rest from data.
4383 */
4384 target -= bytes;
4385
4386 total_evicted +=
4387 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4388 } else {
4389 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4390 total_evicted += bytes;
4391
4392 /*
4393 * If we couldn't evict our target number of bytes from
4394 * data, we try to get the rest from metadata.
4395 */
4396 target -= bytes;
4397
4398 total_evicted +=
4399 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4400 }
4401
4402 /*
4403 * Adjust MFU size
4404 *
4405 * Now that we've tried to evict enough from the MRU to get its
4406 * size back to arc_p, if we're still above the target cache
4407 * size, we evict the rest from the MFU.
4408 */
4409 target = asize - arc_c;
4410
4411 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
4412 ameta > arc_meta_min) {
4413 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4414 total_evicted += bytes;
4415
4416 /*
4417 * If we couldn't evict our target number of bytes from
4418 * metadata, we try to get the rest from data.
4419 */
4420 target -= bytes;
4421
4422 total_evicted +=
4423 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4424 } else {
4425 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4426 total_evicted += bytes;
4427
4428 /*
4429 * If we couldn't evict our target number of bytes from
4430 * data, we try to get the rest from data.
4431 */
4432 target -= bytes;
4433
4434 total_evicted +=
4435 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4436 }
4437
4438 /*
4439 * Adjust ghost lists
4440 *
4441 * In addition to the above, the ARC also defines target values
4442 * for the ghost lists. The sum of the mru list and mru ghost
4443 * list should never exceed the target size of the cache, and
4444 * the sum of the mru list, mfu list, mru ghost list, and mfu
4445 * ghost list should never exceed twice the target size of the
4446 * cache. The following logic enforces these limits on the ghost
4447 * caches, and evicts from them as needed.
4448 */
4449 target = zfs_refcount_count(&arc_mru->arcs_size) +
4450 zfs_refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
4451
4452 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
4453 total_evicted += bytes;
4454
4455 target -= bytes;
4456
4457 total_evicted +=
4458 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
4459
4460 /*
4461 * We assume the sum of the mru list and mfu list is less than
4462 * or equal to arc_c (we enforced this above), which means we
4463 * can use the simpler of the two equations below:
4464 *
4465 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
4466 * mru ghost + mfu ghost <= arc_c
4467 */
4468 target = zfs_refcount_count(&arc_mru_ghost->arcs_size) +
4469 zfs_refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
4470
4471 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
4472 total_evicted += bytes;
4473
4474 target -= bytes;
4475
4476 total_evicted +=
4477 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
4478
4479 return (total_evicted);
4480 }
4481
4482 void
4483 arc_flush(spa_t *spa, boolean_t retry)
4484 {
4485 uint64_t guid = 0;
4486
4487 /*
4488 * If retry is B_TRUE, a spa must not be specified since we have
4489 * no good way to determine if all of a spa's buffers have been
4490 * evicted from an arc state.
4491 */
4492 ASSERT(!retry || spa == 0);
4493
4494 if (spa != NULL)
4495 guid = spa_load_guid(spa);
4496
4497 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
4498 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
4499
4500 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
4501 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
4502
4503 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
4504 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
4505
4506 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
4507 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
4508 }
4509
4510 static void
4511 arc_reduce_target_size(int64_t to_free)
4512 {
4513 uint64_t asize = aggsum_value(&arc_size);
4514 if (arc_c > arc_c_min) {
4515
4516 if (arc_c > arc_c_min + to_free)
4517 atomic_add_64(&arc_c, -to_free);
4518 else
4519 arc_c = arc_c_min;
4520
4521 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
4522 if (asize < arc_c)
4523 arc_c = MAX(asize, arc_c_min);
4524 if (arc_p > arc_c)
4525 arc_p = (arc_c >> 1);
4526 ASSERT(arc_c >= arc_c_min);
4527 ASSERT((int64_t)arc_p >= 0);
4528 }
4529
4530 if (asize > arc_c) {
4531 /* See comment in arc_adjust_cb_check() on why lock+flag */
4532 mutex_enter(&arc_adjust_lock);
4533 arc_adjust_needed = B_TRUE;
4534 mutex_exit(&arc_adjust_lock);
4535 zthr_wakeup(arc_adjust_zthr);
4536 }
4537 }
4538
4539 typedef enum free_memory_reason_t {
4540 FMR_UNKNOWN,
4541 FMR_NEEDFREE,
4542 FMR_LOTSFREE,
4543 FMR_SWAPFS_MINFREE,
4544 FMR_PAGES_PP_MAXIMUM,
4545 FMR_HEAP_ARENA,
4546 FMR_ZIO_ARENA,
4547 } free_memory_reason_t;
4548
4549 int64_t last_free_memory;
4550 free_memory_reason_t last_free_reason;
4551
4552 /*
4553 * Additional reserve of pages for pp_reserve.
4554 */
4555 int64_t arc_pages_pp_reserve = 64;
4556
4557 /*
4558 * Additional reserve of pages for swapfs.
4559 */
4560 int64_t arc_swapfs_reserve = 64;
4561
4562 /*
4563 * Return the amount of memory that can be consumed before reclaim will be
4564 * needed. Positive if there is sufficient free memory, negative indicates
4565 * the amount of memory that needs to be freed up.
4566 */
4567 static int64_t
4568 arc_available_memory(void)
4569 {
4570 int64_t lowest = INT64_MAX;
4571 int64_t n;
4572 free_memory_reason_t r = FMR_UNKNOWN;
4573
4574 #ifdef _KERNEL
4575 if (needfree > 0) {
4576 n = PAGESIZE * (-needfree);
4577 if (n < lowest) {
4578 lowest = n;
4579 r = FMR_NEEDFREE;
4580 }
4581 }
4582
4583 /*
4584 * check that we're out of range of the pageout scanner. It starts to
4585 * schedule paging if freemem is less than lotsfree and needfree.
4586 * lotsfree is the high-water mark for pageout, and needfree is the
4587 * number of needed free pages. We add extra pages here to make sure
4588 * the scanner doesn't start up while we're freeing memory.
4589 */
4590 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
4591 if (n < lowest) {
4592 lowest = n;
4593 r = FMR_LOTSFREE;
4594 }
4595
4596 /*
4597 * check to make sure that swapfs has enough space so that anon
4598 * reservations can still succeed. anon_resvmem() checks that the
4599 * availrmem is greater than swapfs_minfree, and the number of reserved
4600 * swap pages. We also add a bit of extra here just to prevent
4601 * circumstances from getting really dire.
4602 */
4603 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
4604 desfree - arc_swapfs_reserve);
4605 if (n < lowest) {
4606 lowest = n;
4607 r = FMR_SWAPFS_MINFREE;
4608 }
4609
4610
4611 /*
4612 * Check that we have enough availrmem that memory locking (e.g., via
4613 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
4614 * stores the number of pages that cannot be locked; when availrmem
4615 * drops below pages_pp_maximum, page locking mechanisms such as
4616 * page_pp_lock() will fail.)
4617 */
4618 n = PAGESIZE * (availrmem - pages_pp_maximum -
4619 arc_pages_pp_reserve);
4620 if (n < lowest) {
4621 lowest = n;
4622 r = FMR_PAGES_PP_MAXIMUM;
4623 }
4624
4625 #if defined(__i386)
4626 /*
4627 * If we're on an i386 platform, it's possible that we'll exhaust the
4628 * kernel heap space before we ever run out of available physical
4629 * memory. Most checks of the size of the heap_area compare against
4630 * tune.t_minarmem, which is the minimum available real memory that we
4631 * can have in the system. However, this is generally fixed at 25 pages
4632 * which is so low that it's useless. In this comparison, we seek to
4633 * calculate the total heap-size, and reclaim if more than 3/4ths of the
4634 * heap is allocated. (Or, in the calculation, if less than 1/4th is
4635 * free)
4636 */
4637 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) -
4638 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
4639 if (n < lowest) {
4640 lowest = n;
4641 r = FMR_HEAP_ARENA;
4642 }
4643 #endif
4644
4645 /*
4646 * If zio data pages are being allocated out of a separate heap segment,
4647 * then enforce that the size of available vmem for this arena remains
4648 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free.
4649 *
4650 * Note that reducing the arc_zio_arena_free_shift keeps more virtual
4651 * memory (in the zio_arena) free, which can avoid memory
4652 * fragmentation issues.
4653 */
4654 if (zio_arena != NULL) {
4655 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
4656 (vmem_size(zio_arena, VMEM_ALLOC) >>
4657 arc_zio_arena_free_shift);
4658 if (n < lowest) {
4659 lowest = n;
4660 r = FMR_ZIO_ARENA;
4661 }
4662 }
4663 #else
4664 /* Every 100 calls, free a small amount */
4665 if (spa_get_random(100) == 0)
4666 lowest = -1024;
4667 #endif
4668
4669 last_free_memory = lowest;
4670 last_free_reason = r;
4671
4672 return (lowest);
4673 }
4674
4675
4676 /*
4677 * Determine if the system is under memory pressure and is asking
4678 * to reclaim memory. A return value of B_TRUE indicates that the system
4679 * is under memory pressure and that the arc should adjust accordingly.
4680 */
4681 static boolean_t
4682 arc_reclaim_needed(void)
4683 {
4684 return (arc_available_memory() < 0);
4685 }
4686
4687 static void
4688 arc_kmem_reap_soon(void)
4689 {
4690 size_t i;
4691 kmem_cache_t *prev_cache = NULL;
4692 kmem_cache_t *prev_data_cache = NULL;
4693 extern kmem_cache_t *zio_buf_cache[];
4694 extern kmem_cache_t *zio_data_buf_cache[];
4695 extern kmem_cache_t *zfs_btree_leaf_cache;
4696 extern kmem_cache_t *abd_chunk_cache;
4697
4698 #ifdef _KERNEL
4699 if (aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) {
4700 /*
4701 * We are exceeding our meta-data cache limit.
4702 * Purge some DNLC entries to release holds on meta-data.
4703 */
4704 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
4705 }
4706 #if defined(__i386)
4707 /*
4708 * Reclaim unused memory from all kmem caches.
4709 */
4710 kmem_reap();
4711 #endif
4712 #endif
4713
4714 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
4715 if (zio_buf_cache[i] != prev_cache) {
4716 prev_cache = zio_buf_cache[i];
4717 kmem_cache_reap_soon(zio_buf_cache[i]);
4718 }
4719 if (zio_data_buf_cache[i] != prev_data_cache) {
4720 prev_data_cache = zio_data_buf_cache[i];
4721 kmem_cache_reap_soon(zio_data_buf_cache[i]);
4722 }
4723 }
4724 kmem_cache_reap_soon(abd_chunk_cache);
4725 kmem_cache_reap_soon(buf_cache);
4726 kmem_cache_reap_soon(hdr_full_cache);
4727 kmem_cache_reap_soon(hdr_l2only_cache);
4728 kmem_cache_reap_soon(zfs_btree_leaf_cache);
4729
4730 if (zio_arena != NULL) {
4731 /*
4732 * Ask the vmem arena to reclaim unused memory from its
4733 * quantum caches.
4734 */
4735 vmem_qcache_reap(zio_arena);
4736 }
4737 }
4738
4739 /* ARGSUSED */
4740 static boolean_t
4741 arc_adjust_cb_check(void *arg, zthr_t *zthr)
4742 {
4743 /*
4744 * This is necessary in order for the mdb ::arc dcmd to
4745 * show up to date information. Since the ::arc command
4746 * does not call the kstat's update function, without
4747 * this call, the command may show stale stats for the
4748 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
4749 * with this change, the data might be up to 1 second
4750 * out of date(the arc_adjust_zthr has a maximum sleep
4751 * time of 1 second); but that should suffice. The
4752 * arc_state_t structures can be queried directly if more
4753 * accurate information is needed.
4754 */
4755 if (arc_ksp != NULL)
4756 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
4757
4758 /*
4759 * We have to rely on arc_get_data_impl() to tell us when to adjust,
4760 * rather than checking if we are overflowing here, so that we are
4761 * sure to not leave arc_get_data_impl() waiting on
4762 * arc_adjust_waiters_cv. If we have become "not overflowing" since
4763 * arc_get_data_impl() checked, we need to wake it up. We could
4764 * broadcast the CV here, but arc_get_data_impl() may have not yet
4765 * gone to sleep. We would need to use a mutex to ensure that this
4766 * function doesn't broadcast until arc_get_data_impl() has gone to
4767 * sleep (e.g. the arc_adjust_lock). However, the lock ordering of
4768 * such a lock would necessarily be incorrect with respect to the
4769 * zthr_lock, which is held before this function is called, and is
4770 * held by arc_get_data_impl() when it calls zthr_wakeup().
4771 */
4772 return (arc_adjust_needed);
4773 }
4774
4775 /*
4776 * Keep arc_size under arc_c by running arc_adjust which evicts data
4777 * from the ARC.
4778 */
4779 /* ARGSUSED */
4780 static void
4781 arc_adjust_cb(void *arg, zthr_t *zthr)
4782 {
4783 uint64_t evicted = 0;
4784
4785 /* Evict from cache */
4786 evicted = arc_adjust();
4787
4788 /*
4789 * If evicted is zero, we couldn't evict anything
4790 * via arc_adjust(). This could be due to hash lock
4791 * collisions, but more likely due to the majority of
4792 * arc buffers being unevictable. Therefore, even if
4793 * arc_size is above arc_c, another pass is unlikely to
4794 * be helpful and could potentially cause us to enter an
4795 * infinite loop. Additionally, zthr_iscancelled() is
4796 * checked here so that if the arc is shutting down, the
4797 * broadcast will wake any remaining arc adjust waiters.
4798 */
4799 mutex_enter(&arc_adjust_lock);
4800 arc_adjust_needed = !zthr_iscancelled(arc_adjust_zthr) &&
4801 evicted > 0 && aggsum_compare(&arc_size, arc_c) > 0;
4802 if (!arc_adjust_needed) {
4803 /*
4804 * We're either no longer overflowing, or we
4805 * can't evict anything more, so we should wake
4806 * up any waiters.
4807 */
4808 cv_broadcast(&arc_adjust_waiters_cv);
4809 }
4810 mutex_exit(&arc_adjust_lock);
4811 }
4812
4813 /* ARGSUSED */
4814 static boolean_t
4815 arc_reap_cb_check(void *arg, zthr_t *zthr)
4816 {
4817 int64_t free_memory = arc_available_memory();
4818
4819 /*
4820 * If a kmem reap is already active, don't schedule more. We must
4821 * check for this because kmem_cache_reap_soon() won't actually
4822 * block on the cache being reaped (this is to prevent callers from
4823 * becoming implicitly blocked by a system-wide kmem reap -- which,
4824 * on a system with many, many full magazines, can take minutes).
4825 */
4826 if (!kmem_cache_reap_active() &&
4827 free_memory < 0) {
4828 arc_no_grow = B_TRUE;
4829 arc_warm = B_TRUE;
4830 /*
4831 * Wait at least zfs_grow_retry (default 60) seconds
4832 * before considering growing.
4833 */
4834 arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
4835 return (B_TRUE);
4836 } else if (free_memory < arc_c >> arc_no_grow_shift) {
4837 arc_no_grow = B_TRUE;
4838 } else if (gethrtime() >= arc_growtime) {
4839 arc_no_grow = B_FALSE;
4840 }
4841
4842 return (B_FALSE);
4843 }
4844
4845 /*
4846 * Keep enough free memory in the system by reaping the ARC's kmem
4847 * caches. To cause more slabs to be reapable, we may reduce the
4848 * target size of the cache (arc_c), causing the arc_adjust_cb()
4849 * to free more buffers.
4850 */
4851 /* ARGSUSED */
4852 static void
4853 arc_reap_cb(void *arg, zthr_t *zthr)
4854 {
4855 int64_t free_memory;
4856
4857 /*
4858 * Kick off asynchronous kmem_reap()'s of all our caches.
4859 */
4860 arc_kmem_reap_soon();
4861
4862 /*
4863 * Wait at least arc_kmem_cache_reap_retry_ms between
4864 * arc_kmem_reap_soon() calls. Without this check it is possible to
4865 * end up in a situation where we spend lots of time reaping
4866 * caches, while we're near arc_c_min. Waiting here also gives the
4867 * subsequent free memory check a chance of finding that the
4868 * asynchronous reap has already freed enough memory, and we don't
4869 * need to call arc_reduce_target_size().
4870 */
4871 delay((hz * arc_kmem_cache_reap_retry_ms + 999) / 1000);
4872
4873 /*
4874 * Reduce the target size as needed to maintain the amount of free
4875 * memory in the system at a fraction of the arc_size (1/128th by
4876 * default). If oversubscribed (free_memory < 0) then reduce the
4877 * target arc_size by the deficit amount plus the fractional
4878 * amount. If free memory is positive but less then the fractional
4879 * amount, reduce by what is needed to hit the fractional amount.
4880 */
4881 free_memory = arc_available_memory();
4882
4883 int64_t to_free =
4884 (arc_c >> arc_shrink_shift) - free_memory;
4885 if (to_free > 0) {
4886 #ifdef _KERNEL
4887 to_free = MAX(to_free, ptob(needfree));
4888 #endif
4889 arc_reduce_target_size(to_free);
4890 }
4891 }
4892
4893 /*
4894 * Adapt arc info given the number of bytes we are trying to add and
4895 * the state that we are coming from. This function is only called
4896 * when we are adding new content to the cache.
4897 */
4898 static void
4899 arc_adapt(int bytes, arc_state_t *state)
4900 {
4901 int mult;
4902 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
4903 int64_t mrug_size = zfs_refcount_count(&arc_mru_ghost->arcs_size);
4904 int64_t mfug_size = zfs_refcount_count(&arc_mfu_ghost->arcs_size);
4905
4906 ASSERT(bytes > 0);
4907 /*
4908 * Adapt the target size of the MRU list:
4909 * - if we just hit in the MRU ghost list, then increase
4910 * the target size of the MRU list.
4911 * - if we just hit in the MFU ghost list, then increase
4912 * the target size of the MFU list by decreasing the
4913 * target size of the MRU list.
4914 */
4915 if (state == arc_mru_ghost) {
4916 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
4917 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
4918
4919 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
4920 } else if (state == arc_mfu_ghost) {
4921 uint64_t delta;
4922
4923 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
4924 mult = MIN(mult, 10);
4925
4926 delta = MIN(bytes * mult, arc_p);
4927 arc_p = MAX(arc_p_min, arc_p - delta);
4928 }
4929 ASSERT((int64_t)arc_p >= 0);
4930
4931 /*
4932 * Wake reap thread if we do not have any available memory
4933 */
4934 if (arc_reclaim_needed()) {
4935 zthr_wakeup(arc_reap_zthr);
4936 return;
4937 }
4938
4939
4940 if (arc_no_grow)
4941 return;
4942
4943 if (arc_c >= arc_c_max)
4944 return;
4945
4946 /*
4947 * If we're within (2 * maxblocksize) bytes of the target
4948 * cache size, increment the target cache size
4949 */
4950 if (aggsum_compare(&arc_size, arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) >
4951 0) {
4952 atomic_add_64(&arc_c, (int64_t)bytes);
4953 if (arc_c > arc_c_max)
4954 arc_c = arc_c_max;
4955 else if (state == arc_anon)
4956 atomic_add_64(&arc_p, (int64_t)bytes);
4957 if (arc_p > arc_c)
4958 arc_p = arc_c;
4959 }
4960 ASSERT((int64_t)arc_p >= 0);
4961 }
4962
4963 /*
4964 * Check if arc_size has grown past our upper threshold, determined by
4965 * zfs_arc_overflow_shift.
4966 */
4967 static boolean_t
4968 arc_is_overflowing(void)
4969 {
4970 /* Always allow at least one block of overflow */
4971 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
4972 arc_c >> zfs_arc_overflow_shift);
4973
4974 /*
4975 * We just compare the lower bound here for performance reasons. Our
4976 * primary goals are to make sure that the arc never grows without
4977 * bound, and that it can reach its maximum size. This check
4978 * accomplishes both goals. The maximum amount we could run over by is
4979 * 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block
4980 * in the ARC. In practice, that's in the tens of MB, which is low
4981 * enough to be safe.
4982 */
4983 return (aggsum_lower_bound(&arc_size) >= arc_c + overflow);
4984 }
4985
4986 static abd_t *
4987 arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag,
4988 boolean_t do_adapt)
4989 {
4990 arc_buf_contents_t type = arc_buf_type(hdr);
4991
4992 arc_get_data_impl(hdr, size, tag, do_adapt);
4993 if (type == ARC_BUFC_METADATA) {
4994 return (abd_alloc(size, B_TRUE));
4995 } else {
4996 ASSERT(type == ARC_BUFC_DATA);
4997 return (abd_alloc(size, B_FALSE));
4998 }
4999 }
5000
5001 static void *
5002 arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5003 {
5004 arc_buf_contents_t type = arc_buf_type(hdr);
5005
5006 arc_get_data_impl(hdr, size, tag, B_TRUE);
5007 if (type == ARC_BUFC_METADATA) {
5008 return (zio_buf_alloc(size));
5009 } else {
5010 ASSERT(type == ARC_BUFC_DATA);
5011 return (zio_data_buf_alloc(size));
5012 }
5013 }
5014
5015 /*
5016 * Allocate a block and return it to the caller. If we are hitting the
5017 * hard limit for the cache size, we must sleep, waiting for the eviction
5018 * thread to catch up. If we're past the target size but below the hard
5019 * limit, we'll only signal the reclaim thread and continue on.
5020 */
5021 static void
5022 arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag,
5023 boolean_t do_adapt)
5024 {
5025 arc_state_t *state = hdr->b_l1hdr.b_state;
5026 arc_buf_contents_t type = arc_buf_type(hdr);
5027
5028 if (do_adapt)
5029 arc_adapt(size, state);
5030
5031 /*
5032 * If arc_size is currently overflowing, and has grown past our
5033 * upper limit, we must be adding data faster than the evict
5034 * thread can evict. Thus, to ensure we don't compound the
5035 * problem by adding more data and forcing arc_size to grow even
5036 * further past its target size, we halt and wait for the
5037 * eviction thread to catch up.
5038 *
5039 * It's also possible that the reclaim thread is unable to evict
5040 * enough buffers to get arc_size below the overflow limit (e.g.
5041 * due to buffers being un-evictable, or hash lock collisions).
5042 * In this case, we want to proceed regardless if we're
5043 * overflowing; thus we don't use a while loop here.
5044 */
5045 if (arc_is_overflowing()) {
5046 mutex_enter(&arc_adjust_lock);
5047
5048 /*
5049 * Now that we've acquired the lock, we may no longer be
5050 * over the overflow limit, lets check.
5051 *
5052 * We're ignoring the case of spurious wake ups. If that
5053 * were to happen, it'd let this thread consume an ARC
5054 * buffer before it should have (i.e. before we're under
5055 * the overflow limit and were signalled by the reclaim
5056 * thread). As long as that is a rare occurrence, it
5057 * shouldn't cause any harm.
5058 */
5059 if (arc_is_overflowing()) {
5060 arc_adjust_needed = B_TRUE;
5061 zthr_wakeup(arc_adjust_zthr);
5062 (void) cv_wait(&arc_adjust_waiters_cv,
5063 &arc_adjust_lock);
5064 }
5065 mutex_exit(&arc_adjust_lock);
5066 }
5067
5068 VERIFY3U(hdr->b_type, ==, type);
5069 if (type == ARC_BUFC_METADATA) {
5070 arc_space_consume(size, ARC_SPACE_META);
5071 } else {
5072 arc_space_consume(size, ARC_SPACE_DATA);
5073 }
5074
5075 /*
5076 * Update the state size. Note that ghost states have a
5077 * "ghost size" and so don't need to be updated.
5078 */
5079 if (!GHOST_STATE(state)) {
5080
5081 (void) zfs_refcount_add_many(&state->arcs_size, size, tag);
5082
5083 /*
5084 * If this is reached via arc_read, the link is
5085 * protected by the hash lock. If reached via
5086 * arc_buf_alloc, the header should not be accessed by
5087 * any other thread. And, if reached via arc_read_done,
5088 * the hash lock will protect it if it's found in the
5089 * hash table; otherwise no other thread should be
5090 * trying to [add|remove]_reference it.
5091 */
5092 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
5093 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5094 (void) zfs_refcount_add_many(&state->arcs_esize[type],
5095 size, tag);
5096 }
5097
5098 /*
5099 * If we are growing the cache, and we are adding anonymous
5100 * data, and we have outgrown arc_p, update arc_p
5101 */
5102 if (aggsum_compare(&arc_size, arc_c) < 0 &&
5103 hdr->b_l1hdr.b_state == arc_anon &&
5104 (zfs_refcount_count(&arc_anon->arcs_size) +
5105 zfs_refcount_count(&arc_mru->arcs_size) > arc_p))
5106 arc_p = MIN(arc_c, arc_p + size);
5107 }
5108 }
5109
5110 static void
5111 arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag)
5112 {
5113 arc_free_data_impl(hdr, size, tag);
5114 abd_free(abd);
5115 }
5116
5117 static void
5118 arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag)
5119 {
5120 arc_buf_contents_t type = arc_buf_type(hdr);
5121
5122 arc_free_data_impl(hdr, size, tag);
5123 if (type == ARC_BUFC_METADATA) {
5124 zio_buf_free(buf, size);
5125 } else {
5126 ASSERT(type == ARC_BUFC_DATA);
5127 zio_data_buf_free(buf, size);
5128 }
5129 }
5130
5131 /*
5132 * Free the arc data buffer.
5133 */
5134 static void
5135 arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5136 {
5137 arc_state_t *state = hdr->b_l1hdr.b_state;
5138 arc_buf_contents_t type = arc_buf_type(hdr);
5139
5140 /* protected by hash lock, if in the hash table */
5141 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
5142 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5143 ASSERT(state != arc_anon && state != arc_l2c_only);
5144
5145 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
5146 size, tag);
5147 }
5148 (void) zfs_refcount_remove_many(&state->arcs_size, size, tag);
5149
5150 VERIFY3U(hdr->b_type, ==, type);
5151 if (type == ARC_BUFC_METADATA) {
5152 arc_space_return(size, ARC_SPACE_META);
5153 } else {
5154 ASSERT(type == ARC_BUFC_DATA);
5155 arc_space_return(size, ARC_SPACE_DATA);
5156 }
5157 }
5158
5159 /*
5160 * This routine is called whenever a buffer is accessed.
5161 * NOTE: the hash lock is dropped in this function.
5162 */
5163 static void
5164 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
5165 {
5166 clock_t now;
5167
5168 ASSERT(MUTEX_HELD(hash_lock));
5169 ASSERT(HDR_HAS_L1HDR(hdr));
5170
5171 if (hdr->b_l1hdr.b_state == arc_anon) {
5172 /*
5173 * This buffer is not in the cache, and does not
5174 * appear in our "ghost" list. Add the new buffer
5175 * to the MRU state.
5176 */
5177
5178 ASSERT0(hdr->b_l1hdr.b_arc_access);
5179 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5180 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5181 arc_change_state(arc_mru, hdr, hash_lock);
5182
5183 } else if (hdr->b_l1hdr.b_state == arc_mru) {
5184 now = ddi_get_lbolt();
5185
5186 /*
5187 * If this buffer is here because of a prefetch, then either:
5188 * - clear the flag if this is a "referencing" read
5189 * (any subsequent access will bump this into the MFU state).
5190 * or
5191 * - move the buffer to the head of the list if this is
5192 * another prefetch (to make it less likely to be evicted).
5193 */
5194 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5195 if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
5196 /* link protected by hash lock */
5197 ASSERT(multilist_link_active(
5198 &hdr->b_l1hdr.b_arc_node));
5199 } else {
5200 if (HDR_HAS_L2HDR(hdr))
5201 l2arc_hdr_arcstats_decrement_state(hdr);
5202 arc_hdr_clear_flags(hdr,
5203 ARC_FLAG_PREFETCH |
5204 ARC_FLAG_PRESCIENT_PREFETCH);
5205 ARCSTAT_BUMP(arcstat_mru_hits);
5206 if (HDR_HAS_L2HDR(hdr))
5207 l2arc_hdr_arcstats_increment_state(hdr);
5208 }
5209 hdr->b_l1hdr.b_arc_access = now;
5210 return;
5211 }
5212
5213 /*
5214 * This buffer has been "accessed" only once so far,
5215 * but it is still in the cache. Move it to the MFU
5216 * state.
5217 */
5218 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
5219 /*
5220 * More than 125ms have passed since we
5221 * instantiated this buffer. Move it to the
5222 * most frequently used state.
5223 */
5224 hdr->b_l1hdr.b_arc_access = now;
5225 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5226 arc_change_state(arc_mfu, hdr, hash_lock);
5227 }
5228 ARCSTAT_BUMP(arcstat_mru_hits);
5229 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
5230 arc_state_t *new_state;
5231 /*
5232 * This buffer has been "accessed" recently, but
5233 * was evicted from the cache. Move it to the
5234 * MFU state.
5235 */
5236 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5237 new_state = arc_mru;
5238 if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) {
5239 if (HDR_HAS_L2HDR(hdr))
5240 l2arc_hdr_arcstats_decrement_state(hdr);
5241 arc_hdr_clear_flags(hdr,
5242 ARC_FLAG_PREFETCH |
5243 ARC_FLAG_PRESCIENT_PREFETCH);
5244 if (HDR_HAS_L2HDR(hdr))
5245 l2arc_hdr_arcstats_increment_state(hdr);
5246 }
5247 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5248 } else {
5249 new_state = arc_mfu;
5250 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5251 }
5252
5253 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5254 arc_change_state(new_state, hdr, hash_lock);
5255
5256 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
5257 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
5258 /*
5259 * This buffer has been accessed more than once and is
5260 * still in the cache. Keep it in the MFU state.
5261 *
5262 * NOTE: an add_reference() that occurred when we did
5263 * the arc_read() will have kicked this off the list.
5264 * If it was a prefetch, we will explicitly move it to
5265 * the head of the list now.
5266 */
5267 ARCSTAT_BUMP(arcstat_mfu_hits);
5268 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5269 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
5270 arc_state_t *new_state = arc_mfu;
5271 /*
5272 * This buffer has been accessed more than once but has
5273 * been evicted from the cache. Move it back to the
5274 * MFU state.
5275 */
5276
5277 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5278 /*
5279 * This is a prefetch access...
5280 * move this block back to the MRU state.
5281 */
5282 new_state = arc_mru;
5283 }
5284
5285 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5286 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5287 arc_change_state(new_state, hdr, hash_lock);
5288
5289 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
5290 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
5291 /*
5292 * This buffer is on the 2nd Level ARC.
5293 */
5294
5295 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5296 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5297 arc_change_state(arc_mfu, hdr, hash_lock);
5298 } else {
5299 ASSERT(!"invalid arc state");
5300 }
5301 }
5302
5303 /*
5304 * This routine is called by dbuf_hold() to update the arc_access() state
5305 * which otherwise would be skipped for entries in the dbuf cache.
5306 */
5307 void
5308 arc_buf_access(arc_buf_t *buf)
5309 {
5310 mutex_enter(&buf->b_evict_lock);
5311 arc_buf_hdr_t *hdr = buf->b_hdr;
5312
5313 /*
5314 * Avoid taking the hash_lock when possible as an optimization.
5315 * The header must be checked again under the hash_lock in order
5316 * to handle the case where it is concurrently being released.
5317 */
5318 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5319 mutex_exit(&buf->b_evict_lock);
5320 return;
5321 }
5322
5323 kmutex_t *hash_lock = HDR_LOCK(hdr);
5324 mutex_enter(hash_lock);
5325
5326 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5327 mutex_exit(hash_lock);
5328 mutex_exit(&buf->b_evict_lock);
5329 ARCSTAT_BUMP(arcstat_access_skip);
5330 return;
5331 }
5332
5333 mutex_exit(&buf->b_evict_lock);
5334
5335 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5336 hdr->b_l1hdr.b_state == arc_mfu);
5337
5338 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5339 arc_access(hdr, hash_lock);
5340 mutex_exit(hash_lock);
5341
5342 ARCSTAT_BUMP(arcstat_hits);
5343 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5344 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits);
5345 }
5346
5347 /* a generic arc_read_done_func_t which you can use */
5348 /* ARGSUSED */
5349 void
5350 arc_bcopy_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
5351 arc_buf_t *buf, void *arg)
5352 {
5353 if (buf == NULL)
5354 return;
5355
5356 bcopy(buf->b_data, arg, arc_buf_size(buf));
5357 arc_buf_destroy(buf, arg);
5358 }
5359
5360 /* a generic arc_read_done_func_t */
5361 void
5362 arc_getbuf_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
5363 arc_buf_t *buf, void *arg)
5364 {
5365 arc_buf_t **bufp = arg;
5366
5367 if (buf == NULL) {
5368 ASSERT(zio == NULL || zio->io_error != 0);
5369 *bufp = NULL;
5370 } else {
5371 ASSERT(zio == NULL || zio->io_error == 0);
5372 *bufp = buf;
5373 ASSERT(buf->b_data != NULL);
5374 }
5375 }
5376
5377 static void
5378 arc_hdr_verify(arc_buf_hdr_t *hdr, const blkptr_t *bp)
5379 {
5380 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
5381 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
5382 ASSERT3U(arc_hdr_get_compress(hdr), ==, ZIO_COMPRESS_OFF);
5383 } else {
5384 if (HDR_COMPRESSION_ENABLED(hdr)) {
5385 ASSERT3U(arc_hdr_get_compress(hdr), ==,
5386 BP_GET_COMPRESS(bp));
5387 }
5388 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
5389 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
5390 ASSERT3U(!!HDR_PROTECTED(hdr), ==, BP_IS_PROTECTED(bp));
5391 }
5392 }
5393
5394 /*
5395 * XXX this should be changed to return an error, and callers
5396 * re-read from disk on failure (on nondebug bits).
5397 */
5398 static void
5399 arc_hdr_verify_checksum(spa_t *spa, arc_buf_hdr_t *hdr, const blkptr_t *bp)
5400 {
5401 arc_hdr_verify(hdr, bp);
5402 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp))
5403 return;
5404 int err = 0;
5405 abd_t *abd = NULL;
5406 if (BP_IS_ENCRYPTED(bp)) {
5407 if (HDR_HAS_RABD(hdr)) {
5408 abd = hdr->b_crypt_hdr.b_rabd;
5409 }
5410 } else if (HDR_COMPRESSION_ENABLED(hdr)) {
5411 abd = hdr->b_l1hdr.b_pabd;
5412 }
5413 if (abd != NULL) {
5414 /*
5415 * The offset is only used for labels, which are not
5416 * cached in the ARC, so it doesn't matter what we
5417 * pass for the offset parameter.
5418 */
5419 int psize = HDR_GET_PSIZE(hdr);
5420 err = zio_checksum_error_impl(spa, bp,
5421 BP_GET_CHECKSUM(bp), abd, psize, 0, NULL);
5422 if (err != 0) {
5423 /*
5424 * Use abd_copy_to_buf() rather than
5425 * abd_borrow_buf_copy() so that we are sure to
5426 * include the buf in crash dumps.
5427 */
5428 void *buf = kmem_alloc(psize, KM_SLEEP);
5429 abd_copy_to_buf(buf, abd, psize);
5430 panic("checksum of cached data doesn't match BP "
5431 "err=%u hdr=%p bp=%p abd=%p buf=%p",
5432 err, (void *)hdr, (void *)bp, (void *)abd, buf);
5433 }
5434 }
5435 }
5436
5437 static void
5438 arc_read_done(zio_t *zio)
5439 {
5440 blkptr_t *bp = zio->io_bp;
5441 arc_buf_hdr_t *hdr = zio->io_private;
5442 kmutex_t *hash_lock = NULL;
5443 arc_callback_t *callback_list;
5444 arc_callback_t *acb;
5445 boolean_t freeable = B_FALSE;
5446
5447 /*
5448 * The hdr was inserted into hash-table and removed from lists
5449 * prior to starting I/O. We should find this header, since
5450 * it's in the hash table, and it should be legit since it's
5451 * not possible to evict it during the I/O. The only possible
5452 * reason for it not to be found is if we were freed during the
5453 * read.
5454 */
5455 if (HDR_IN_HASH_TABLE(hdr)) {
5456 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
5457 ASSERT3U(hdr->b_dva.dva_word[0], ==,
5458 BP_IDENTITY(zio->io_bp)->dva_word[0]);
5459 ASSERT3U(hdr->b_dva.dva_word[1], ==,
5460 BP_IDENTITY(zio->io_bp)->dva_word[1]);
5461
5462 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
5463 &hash_lock);
5464
5465 ASSERT((found == hdr &&
5466 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
5467 (found == hdr && HDR_L2_READING(hdr)));
5468 ASSERT3P(hash_lock, !=, NULL);
5469 }
5470
5471 if (BP_IS_PROTECTED(bp)) {
5472 hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp);
5473 hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset;
5474 zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt,
5475 hdr->b_crypt_hdr.b_iv);
5476
5477 if (BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG) {
5478 void *tmpbuf;
5479
5480 tmpbuf = abd_borrow_buf_copy(zio->io_abd,
5481 sizeof (zil_chain_t));
5482 zio_crypt_decode_mac_zil(tmpbuf,
5483 hdr->b_crypt_hdr.b_mac);
5484 abd_return_buf(zio->io_abd, tmpbuf,
5485 sizeof (zil_chain_t));
5486 } else {
5487 zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac);
5488 }
5489 }
5490
5491 if (zio->io_error == 0) {
5492 /* byteswap if necessary */
5493 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
5494 if (BP_GET_LEVEL(zio->io_bp) > 0) {
5495 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
5496 } else {
5497 hdr->b_l1hdr.b_byteswap =
5498 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
5499 }
5500 } else {
5501 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
5502 }
5503 }
5504
5505 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
5506
5507 callback_list = hdr->b_l1hdr.b_acb;
5508 ASSERT3P(callback_list, !=, NULL);
5509
5510 if (hash_lock && zio->io_error == 0 &&
5511 hdr->b_l1hdr.b_state == arc_anon) {
5512 /*
5513 * Only call arc_access on anonymous buffers. This is because
5514 * if we've issued an I/O for an evicted buffer, we've already
5515 * called arc_access (to prevent any simultaneous readers from
5516 * getting confused).
5517 */
5518 arc_access(hdr, hash_lock);
5519 }
5520
5521 /*
5522 * If a read request has a callback (i.e. acb_done is not NULL), then we
5523 * make a buf containing the data according to the parameters which were
5524 * passed in. The implementation of arc_buf_alloc_impl() ensures that we
5525 * aren't needlessly decompressing the data multiple times.
5526 */
5527 int callback_cnt = 0;
5528 for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
5529 if (!acb->acb_done)
5530 continue;
5531
5532 callback_cnt++;
5533
5534 if (zio->io_error != 0)
5535 continue;
5536
5537 int error = arc_buf_alloc_impl(hdr, zio->io_spa,
5538 &acb->acb_zb, acb->acb_private, acb->acb_encrypted,
5539 acb->acb_compressed, acb->acb_noauth, B_TRUE,
5540 &acb->acb_buf);
5541
5542 /*
5543 * Assert non-speculative zios didn't fail because an
5544 * encryption key wasn't loaded
5545 */
5546 ASSERT((zio->io_flags & ZIO_FLAG_SPECULATIVE) ||
5547 error != EACCES);
5548
5549 /*
5550 * If we failed to decrypt, report an error now (as the zio
5551 * layer would have done if it had done the transforms).
5552 */
5553 if (error == ECKSUM) {
5554 ASSERT(BP_IS_PROTECTED(bp));
5555 error = SET_ERROR(EIO);
5556 if ((zio->io_flags & ZIO_FLAG_SPECULATIVE) == 0) {
5557 spa_log_error(zio->io_spa, &acb->acb_zb);
5558 (void) zfs_ereport_post(
5559 FM_EREPORT_ZFS_AUTHENTICATION,
5560 zio->io_spa, NULL, &acb->acb_zb, zio, 0, 0);
5561 }
5562 }
5563
5564 if (error != 0) {
5565 /*
5566 * Decompression failed. Set io_error
5567 * so that when we call acb_done (below),
5568 * we will indicate that the read failed.
5569 * Note that in the unusual case where one
5570 * callback is compressed and another
5571 * uncompressed, we will mark all of them
5572 * as failed, even though the uncompressed
5573 * one can't actually fail. In this case,
5574 * the hdr will not be anonymous, because
5575 * if there are multiple callbacks, it's
5576 * because multiple threads found the same
5577 * arc buf in the hash table.
5578 */
5579 zio->io_error = error;
5580 }
5581 }
5582
5583 /*
5584 * If there are multiple callbacks, we must have the hash lock,
5585 * because the only way for multiple threads to find this hdr is
5586 * in the hash table. This ensures that if there are multiple
5587 * callbacks, the hdr is not anonymous. If it were anonymous,
5588 * we couldn't use arc_buf_destroy() in the error case below.
5589 */
5590 ASSERT(callback_cnt < 2 || hash_lock != NULL);
5591
5592 hdr->b_l1hdr.b_acb = NULL;
5593 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5594 if (callback_cnt == 0)
5595 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
5596
5597 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
5598 callback_list != NULL);
5599
5600 if (zio->io_error == 0) {
5601 arc_hdr_verify(hdr, zio->io_bp);
5602 } else {
5603 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
5604 if (hdr->b_l1hdr.b_state != arc_anon)
5605 arc_change_state(arc_anon, hdr, hash_lock);
5606 if (HDR_IN_HASH_TABLE(hdr))
5607 buf_hash_remove(hdr);
5608 freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5609 }
5610
5611 /*
5612 * Broadcast before we drop the hash_lock to avoid the possibility
5613 * that the hdr (and hence the cv) might be freed before we get to
5614 * the cv_broadcast().
5615 */
5616 cv_broadcast(&hdr->b_l1hdr.b_cv);
5617
5618 if (hash_lock != NULL) {
5619 mutex_exit(hash_lock);
5620 } else {
5621 /*
5622 * This block was freed while we waited for the read to
5623 * complete. It has been removed from the hash table and
5624 * moved to the anonymous state (so that it won't show up
5625 * in the cache).
5626 */
5627 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
5628 freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5629 }
5630
5631 /* execute each callback and free its structure */
5632 while ((acb = callback_list) != NULL) {
5633
5634 if (acb->acb_done != NULL) {
5635 if (zio->io_error != 0 && acb->acb_buf != NULL) {
5636 /*
5637 * If arc_buf_alloc_impl() fails during
5638 * decompression, the buf will still be
5639 * allocated, and needs to be freed here.
5640 */
5641 arc_buf_destroy(acb->acb_buf, acb->acb_private);
5642 acb->acb_buf = NULL;
5643 }
5644 acb->acb_done(zio, &zio->io_bookmark, zio->io_bp,
5645 acb->acb_buf, acb->acb_private);
5646 }
5647
5648 if (acb->acb_zio_dummy != NULL) {
5649 acb->acb_zio_dummy->io_error = zio->io_error;
5650 zio_nowait(acb->acb_zio_dummy);
5651 }
5652
5653 callback_list = acb->acb_next;
5654 kmem_free(acb, sizeof (arc_callback_t));
5655 }
5656
5657 if (freeable)
5658 arc_hdr_destroy(hdr);
5659 }
5660
5661 /*
5662 * "Read" the block at the specified DVA (in bp) via the
5663 * cache. If the block is found in the cache, invoke the provided
5664 * callback immediately and return. Note that the `zio' parameter
5665 * in the callback will be NULL in this case, since no IO was
5666 * required. If the block is not in the cache pass the read request
5667 * on to the spa with a substitute callback function, so that the
5668 * requested block will be added to the cache.
5669 *
5670 * If a read request arrives for a block that has a read in-progress,
5671 * either wait for the in-progress read to complete (and return the
5672 * results); or, if this is a read with a "done" func, add a record
5673 * to the read to invoke the "done" func when the read completes,
5674 * and return; or just return.
5675 *
5676 * arc_read_done() will invoke all the requested "done" functions
5677 * for readers of this block.
5678 */
5679 int
5680 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_read_done_func_t *done,
5681 void *private, zio_priority_t priority, int zio_flags,
5682 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
5683 {
5684 arc_buf_hdr_t *hdr = NULL;
5685 kmutex_t *hash_lock = NULL;
5686 zio_t *rzio;
5687 uint64_t guid = spa_load_guid(spa);
5688 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW_COMPRESS) != 0;
5689 boolean_t encrypted_read = BP_IS_ENCRYPTED(bp) &&
5690 (zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0;
5691 boolean_t noauth_read = BP_IS_AUTHENTICATED(bp) &&
5692 (zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0;
5693 int rc = 0;
5694
5695 ASSERT(!BP_IS_EMBEDDED(bp) ||
5696 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
5697
5698 top:
5699 if (!BP_IS_EMBEDDED(bp)) {
5700 /*
5701 * Embedded BP's have no DVA and require no I/O to "read".
5702 * Create an anonymous arc buf to back it.
5703 */
5704 hdr = buf_hash_find(guid, bp, &hash_lock);
5705 }
5706
5707 /*
5708 * Determine if we have an L1 cache hit or a cache miss. For simplicity
5709 * we maintain encrypted data seperately from compressed / uncompressed
5710 * data. If the user is requesting raw encrypted data and we don't have
5711 * that in the header we will read from disk to guarantee that we can
5712 * get it even if the encryption keys aren't loaded.
5713 */
5714 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && (HDR_HAS_RABD(hdr) ||
5715 (hdr->b_l1hdr.b_pabd != NULL && !encrypted_read))) {
5716 arc_buf_t *buf = NULL;
5717 *arc_flags |= ARC_FLAG_CACHED;
5718
5719 if (HDR_IO_IN_PROGRESS(hdr)) {
5720 zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head;
5721
5722 ASSERT3P(head_zio, !=, NULL);
5723 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
5724 priority == ZIO_PRIORITY_SYNC_READ) {
5725 /*
5726 * This is a sync read that needs to wait for
5727 * an in-flight async read. Request that the
5728 * zio have its priority upgraded.
5729 */
5730 zio_change_priority(head_zio, priority);
5731 DTRACE_PROBE1(arc__async__upgrade__sync,
5732 arc_buf_hdr_t *, hdr);
5733 ARCSTAT_BUMP(arcstat_async_upgrade_sync);
5734 }
5735 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5736 arc_hdr_clear_flags(hdr,
5737 ARC_FLAG_PREDICTIVE_PREFETCH);
5738 }
5739
5740 if (*arc_flags & ARC_FLAG_WAIT) {
5741 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5742 mutex_exit(hash_lock);
5743 goto top;
5744 }
5745 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5746
5747 if (done) {
5748 arc_callback_t *acb = NULL;
5749
5750 acb = kmem_zalloc(sizeof (arc_callback_t),
5751 KM_SLEEP);
5752 acb->acb_done = done;
5753 acb->acb_private = private;
5754 acb->acb_compressed = compressed_read;
5755 acb->acb_encrypted = encrypted_read;
5756 acb->acb_noauth = noauth_read;
5757 acb->acb_zb = *zb;
5758 if (pio != NULL)
5759 acb->acb_zio_dummy = zio_null(pio,
5760 spa, NULL, NULL, NULL, zio_flags);
5761
5762 ASSERT3P(acb->acb_done, !=, NULL);
5763 acb->acb_zio_head = head_zio;
5764 acb->acb_next = hdr->b_l1hdr.b_acb;
5765 hdr->b_l1hdr.b_acb = acb;
5766 mutex_exit(hash_lock);
5767 return (0);
5768 }
5769 mutex_exit(hash_lock);
5770 return (0);
5771 }
5772
5773 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5774 hdr->b_l1hdr.b_state == arc_mfu);
5775
5776 if (done) {
5777 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5778 /*
5779 * This is a demand read which does not have to
5780 * wait for i/o because we did a predictive
5781 * prefetch i/o for it, which has completed.
5782 */
5783 DTRACE_PROBE1(
5784 arc__demand__hit__predictive__prefetch,
5785 arc_buf_hdr_t *, hdr);
5786 ARCSTAT_BUMP(
5787 arcstat_demand_hit_predictive_prefetch);
5788 arc_hdr_clear_flags(hdr,
5789 ARC_FLAG_PREDICTIVE_PREFETCH);
5790 }
5791
5792 if (hdr->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) {
5793 ARCSTAT_BUMP(
5794 arcstat_demand_hit_prescient_prefetch);
5795 arc_hdr_clear_flags(hdr,
5796 ARC_FLAG_PRESCIENT_PREFETCH);
5797 }
5798
5799 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
5800
5801 arc_hdr_verify_checksum(spa, hdr, bp);
5802
5803 /* Get a buf with the desired data in it. */
5804 rc = arc_buf_alloc_impl(hdr, spa, zb, private,
5805 encrypted_read, compressed_read, noauth_read,
5806 B_TRUE, &buf);
5807 if (rc == ECKSUM) {
5808 /*
5809 * Convert authentication and decryption errors
5810 * to EIO (and generate an ereport if needed)
5811 * before leaving the ARC.
5812 */
5813 rc = SET_ERROR(EIO);
5814 if ((zio_flags & ZIO_FLAG_SPECULATIVE) == 0) {
5815 spa_log_error(spa, zb);
5816 (void) zfs_ereport_post(
5817 FM_EREPORT_ZFS_AUTHENTICATION,
5818 spa, NULL, zb, NULL, 0, 0);
5819 }
5820 }
5821 if (rc != 0) {
5822 (void) remove_reference(hdr, hash_lock,
5823 private);
5824 arc_buf_destroy_impl(buf);
5825 buf = NULL;
5826 }
5827 /* assert any errors weren't due to unloaded keys */
5828 ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) ||
5829 rc != EACCES);
5830 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
5831 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
5832 if (HDR_HAS_L2HDR(hdr))
5833 l2arc_hdr_arcstats_decrement_state(hdr);
5834 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5835 if (HDR_HAS_L2HDR(hdr))
5836 l2arc_hdr_arcstats_increment_state(hdr);
5837 }
5838 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5839 arc_access(hdr, hash_lock);
5840 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH)
5841 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
5842 if (*arc_flags & ARC_FLAG_L2CACHE)
5843 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5844 mutex_exit(hash_lock);
5845 ARCSTAT_BUMP(arcstat_hits);
5846 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5847 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5848 data, metadata, hits);
5849
5850 if (done)
5851 done(NULL, zb, bp, buf, private);
5852 } else {
5853 uint64_t lsize = BP_GET_LSIZE(bp);
5854 uint64_t psize = BP_GET_PSIZE(bp);
5855 arc_callback_t *acb;
5856 vdev_t *vd = NULL;
5857 uint64_t addr = 0;
5858 boolean_t devw = B_FALSE;
5859 uint64_t size;
5860 abd_t *hdr_abd;
5861 int alloc_flags = encrypted_read ? ARC_HDR_ALLOC_RDATA : 0;
5862
5863 if (hdr == NULL) {
5864 /* this block is not in the cache */
5865 arc_buf_hdr_t *exists = NULL;
5866 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
5867 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
5868 BP_IS_PROTECTED(bp), BP_GET_COMPRESS(bp), type,
5869 encrypted_read);
5870
5871 if (!BP_IS_EMBEDDED(bp)) {
5872 hdr->b_dva = *BP_IDENTITY(bp);
5873 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
5874 exists = buf_hash_insert(hdr, &hash_lock);
5875 }
5876 if (exists != NULL) {
5877 /* somebody beat us to the hash insert */
5878 mutex_exit(hash_lock);
5879 buf_discard_identity(hdr);
5880 arc_hdr_destroy(hdr);
5881 goto top; /* restart the IO request */
5882 }
5883 } else {
5884 /*
5885 * This block is in the ghost cache or encrypted data
5886 * was requested and we didn't have it. If it was
5887 * L2-only (and thus didn't have an L1 hdr),
5888 * we realloc the header to add an L1 hdr.
5889 */
5890 if (!HDR_HAS_L1HDR(hdr)) {
5891 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
5892 hdr_full_cache);
5893 }
5894
5895 if (GHOST_STATE(hdr->b_l1hdr.b_state)) {
5896 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5897 ASSERT(!HDR_HAS_RABD(hdr));
5898 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5899 ASSERT0(zfs_refcount_count(
5900 &hdr->b_l1hdr.b_refcnt));
5901 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
5902 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
5903 } else if (HDR_IO_IN_PROGRESS(hdr)) {
5904 /*
5905 * If this header already had an IO in progress
5906 * and we are performing another IO to fetch
5907 * encrypted data we must wait until the first
5908 * IO completes so as not to confuse
5909 * arc_read_done(). This should be very rare
5910 * and so the performance impact shouldn't
5911 * matter.
5912 */
5913 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5914 mutex_exit(hash_lock);
5915 goto top;
5916 }
5917
5918 /*
5919 * This is a delicate dance that we play here.
5920 * This hdr might be in the ghost list so we access
5921 * it to move it out of the ghost list before we
5922 * initiate the read. If it's a prefetch then
5923 * it won't have a callback so we'll remove the
5924 * reference that arc_buf_alloc_impl() created. We
5925 * do this after we've called arc_access() to
5926 * avoid hitting an assert in remove_reference().
5927 */
5928 arc_adapt(arc_hdr_size(hdr), hdr->b_l1hdr.b_state);
5929 arc_access(hdr, hash_lock);
5930 arc_hdr_alloc_pabd(hdr, alloc_flags);
5931 }
5932
5933 if (encrypted_read) {
5934 ASSERT(HDR_HAS_RABD(hdr));
5935 size = HDR_GET_PSIZE(hdr);
5936 hdr_abd = hdr->b_crypt_hdr.b_rabd;
5937 zio_flags |= ZIO_FLAG_RAW;
5938 } else {
5939 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5940 size = arc_hdr_size(hdr);
5941 hdr_abd = hdr->b_l1hdr.b_pabd;
5942
5943 if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
5944 zio_flags |= ZIO_FLAG_RAW_COMPRESS;
5945 }
5946
5947 /*
5948 * For authenticated bp's, we do not ask the ZIO layer
5949 * to authenticate them since this will cause the entire
5950 * IO to fail if the key isn't loaded. Instead, we
5951 * defer authentication until arc_buf_fill(), which will
5952 * verify the data when the key is available.
5953 */
5954 if (BP_IS_AUTHENTICATED(bp))
5955 zio_flags |= ZIO_FLAG_RAW_ENCRYPT;
5956 }
5957
5958 if (*arc_flags & ARC_FLAG_PREFETCH &&
5959 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
5960 if (HDR_HAS_L2HDR(hdr))
5961 l2arc_hdr_arcstats_decrement_state(hdr);
5962 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5963 if (HDR_HAS_L2HDR(hdr))
5964 l2arc_hdr_arcstats_increment_state(hdr);
5965 }
5966 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH)
5967 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
5968
5969 if (*arc_flags & ARC_FLAG_L2CACHE)
5970 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5971 if (BP_IS_AUTHENTICATED(bp))
5972 arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH);
5973 if (BP_GET_LEVEL(bp) > 0)
5974 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
5975 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
5976 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
5977 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
5978
5979 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
5980 acb->acb_done = done;
5981 acb->acb_private = private;
5982 acb->acb_compressed = compressed_read;
5983 acb->acb_encrypted = encrypted_read;
5984 acb->acb_noauth = noauth_read;
5985 acb->acb_zb = *zb;
5986
5987 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5988 hdr->b_l1hdr.b_acb = acb;
5989 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5990
5991 if (HDR_HAS_L2HDR(hdr) &&
5992 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
5993 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
5994 addr = hdr->b_l2hdr.b_daddr;
5995 /*
5996 * Lock out L2ARC device removal.
5997 */
5998 if (vdev_is_dead(vd) ||
5999 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
6000 vd = NULL;
6001 }
6002
6003 /*
6004 * We count both async reads and scrub IOs as asynchronous so
6005 * that both can be upgraded in the event of a cache hit while
6006 * the read IO is still in-flight.
6007 */
6008 if (priority == ZIO_PRIORITY_ASYNC_READ ||
6009 priority == ZIO_PRIORITY_SCRUB)
6010 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
6011 else
6012 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
6013
6014 /*
6015 * At this point, we have a level 1 cache miss. Try again in
6016 * L2ARC if possible.
6017 */
6018 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
6019
6020 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
6021 uint64_t, lsize, zbookmark_phys_t *, zb);
6022 ARCSTAT_BUMP(arcstat_misses);
6023 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
6024 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
6025 data, metadata, misses);
6026
6027 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
6028 /*
6029 * Read from the L2ARC if the following are true:
6030 * 1. The L2ARC vdev was previously cached.
6031 * 2. This buffer still has L2ARC metadata.
6032 * 3. This buffer isn't currently writing to the L2ARC.
6033 * 4. The L2ARC entry wasn't evicted, which may
6034 * also have invalidated the vdev.
6035 * 5. This isn't prefetch or l2arc_noprefetch is 0.
6036 */
6037 if (HDR_HAS_L2HDR(hdr) &&
6038 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
6039 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
6040 l2arc_read_callback_t *cb;
6041 abd_t *abd;
6042 uint64_t asize;
6043
6044 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
6045 ARCSTAT_BUMP(arcstat_l2_hits);
6046
6047 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
6048 KM_SLEEP);
6049 cb->l2rcb_hdr = hdr;
6050 cb->l2rcb_bp = *bp;
6051 cb->l2rcb_zb = *zb;
6052 cb->l2rcb_flags = zio_flags;
6053
6054 /*
6055 * When Compressed ARC is disabled, but the
6056 * L2ARC block is compressed, arc_hdr_size()
6057 * will have returned LSIZE rather than PSIZE.
6058 */
6059 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
6060 !HDR_COMPRESSION_ENABLED(hdr) &&
6061 HDR_GET_PSIZE(hdr) != 0) {
6062 size = HDR_GET_PSIZE(hdr);
6063 }
6064
6065 asize = vdev_psize_to_asize(vd, size);
6066 if (asize != size) {
6067 abd = abd_alloc_for_io(asize,
6068 HDR_ISTYPE_METADATA(hdr));
6069 cb->l2rcb_abd = abd;
6070 } else {
6071 abd = hdr_abd;
6072 }
6073
6074 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
6075 addr + asize <= vd->vdev_psize -
6076 VDEV_LABEL_END_SIZE);
6077
6078 /*
6079 * l2arc read. The SCL_L2ARC lock will be
6080 * released by l2arc_read_done().
6081 * Issue a null zio if the underlying buffer
6082 * was squashed to zero size by compression.
6083 */
6084 ASSERT3U(arc_hdr_get_compress(hdr), !=,
6085 ZIO_COMPRESS_EMPTY);
6086 rzio = zio_read_phys(pio, vd, addr,
6087 asize, abd,
6088 ZIO_CHECKSUM_OFF,
6089 l2arc_read_done, cb, priority,
6090 zio_flags | ZIO_FLAG_DONT_CACHE |
6091 ZIO_FLAG_CANFAIL |
6092 ZIO_FLAG_DONT_PROPAGATE |
6093 ZIO_FLAG_DONT_RETRY, B_FALSE);
6094 acb->acb_zio_head = rzio;
6095
6096 if (hash_lock != NULL)
6097 mutex_exit(hash_lock);
6098
6099 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
6100 zio_t *, rzio);
6101 ARCSTAT_INCR(arcstat_l2_read_bytes,
6102 HDR_GET_PSIZE(hdr));
6103
6104 if (*arc_flags & ARC_FLAG_NOWAIT) {
6105 zio_nowait(rzio);
6106 return (0);
6107 }
6108
6109 ASSERT(*arc_flags & ARC_FLAG_WAIT);
6110 if (zio_wait(rzio) == 0)
6111 return (0);
6112
6113 /* l2arc read error; goto zio_read() */
6114 if (hash_lock != NULL)
6115 mutex_enter(hash_lock);
6116 } else {
6117 DTRACE_PROBE1(l2arc__miss,
6118 arc_buf_hdr_t *, hdr);
6119 ARCSTAT_BUMP(arcstat_l2_misses);
6120 if (HDR_L2_WRITING(hdr))
6121 ARCSTAT_BUMP(arcstat_l2_rw_clash);
6122 spa_config_exit(spa, SCL_L2ARC, vd);
6123 }
6124 } else {
6125 if (vd != NULL)
6126 spa_config_exit(spa, SCL_L2ARC, vd);
6127 if (l2arc_ndev != 0) {
6128 DTRACE_PROBE1(l2arc__miss,
6129 arc_buf_hdr_t *, hdr);
6130 ARCSTAT_BUMP(arcstat_l2_misses);
6131 }
6132 }
6133
6134 rzio = zio_read(pio, spa, bp, hdr_abd, size,
6135 arc_read_done, hdr, priority, zio_flags, zb);
6136 acb->acb_zio_head = rzio;
6137
6138 if (hash_lock != NULL)
6139 mutex_exit(hash_lock);
6140
6141 /*
6142 * At this point, this read I/O has already missed in the ARC
6143 * and will be going through to the disk. The I/O throttle
6144 * should delay this I/O if this zone is using more than its I/O
6145 * priority allows.
6146 */
6147 zfs_zone_io_throttle(ZFS_ZONE_IOP_READ);
6148
6149 if (*arc_flags & ARC_FLAG_WAIT)
6150 return (zio_wait(rzio));
6151
6152 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
6153 zio_nowait(rzio);
6154 }
6155 return (rc);
6156 }
6157
6158 /*
6159 * Notify the arc that a block was freed, and thus will never be used again.
6160 */
6161 void
6162 arc_freed(spa_t *spa, const blkptr_t *bp)
6163 {
6164 arc_buf_hdr_t *hdr;
6165 kmutex_t *hash_lock;
6166 uint64_t guid = spa_load_guid(spa);
6167
6168 ASSERT(!BP_IS_EMBEDDED(bp));
6169
6170 hdr = buf_hash_find(guid, bp, &hash_lock);
6171 if (hdr == NULL)
6172 return;
6173
6174 /*
6175 * We might be trying to free a block that is still doing I/O
6176 * (i.e. prefetch) or has a reference (i.e. a dedup-ed,
6177 * dmu_sync-ed block). If this block is being prefetched, then it
6178 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
6179 * until the I/O completes. A block may also have a reference if it is
6180 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would
6181 * have written the new block to its final resting place on disk but
6182 * without the dedup flag set. This would have left the hdr in the MRU
6183 * state and discoverable. When the txg finally syncs it detects that
6184 * the block was overridden in open context and issues an override I/O.
6185 * Since this is a dedup block, the override I/O will determine if the
6186 * block is already in the DDT. If so, then it will replace the io_bp
6187 * with the bp from the DDT and allow the I/O to finish. When the I/O
6188 * reaches the done callback, dbuf_write_override_done, it will
6189 * check to see if the io_bp and io_bp_override are identical.
6190 * If they are not, then it indicates that the bp was replaced with
6191 * the bp in the DDT and the override bp is freed. This allows
6192 * us to arrive here with a reference on a block that is being
6193 * freed. So if we have an I/O in progress, or a reference to
6194 * this hdr, then we don't destroy the hdr.
6195 */
6196 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
6197 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
6198 arc_change_state(arc_anon, hdr, hash_lock);
6199 arc_hdr_destroy(hdr);
6200 mutex_exit(hash_lock);
6201 } else {
6202 mutex_exit(hash_lock);
6203 }
6204
6205 }
6206
6207 /*
6208 * Release this buffer from the cache, making it an anonymous buffer. This
6209 * must be done after a read and prior to modifying the buffer contents.
6210 * If the buffer has more than one reference, we must make
6211 * a new hdr for the buffer.
6212 */
6213 void
6214 arc_release(arc_buf_t *buf, void *tag)
6215 {
6216 arc_buf_hdr_t *hdr = buf->b_hdr;
6217
6218 /*
6219 * It would be nice to assert that if its DMU metadata (level >
6220 * 0 || it's the dnode file), then it must be syncing context.
6221 * But we don't know that information at this level.
6222 */
6223
6224 mutex_enter(&buf->b_evict_lock);
6225
6226 ASSERT(HDR_HAS_L1HDR(hdr));
6227
6228 /*
6229 * We don't grab the hash lock prior to this check, because if
6230 * the buffer's header is in the arc_anon state, it won't be
6231 * linked into the hash table.
6232 */
6233 if (hdr->b_l1hdr.b_state == arc_anon) {
6234 mutex_exit(&buf->b_evict_lock);
6235 /*
6236 * If we are called from dmu_convert_mdn_block_to_raw(),
6237 * a write might be in progress. This is OK because
6238 * the caller won't change the content of this buffer,
6239 * only the flags (via arc_convert_to_raw()).
6240 */
6241 /* ASSERT(!HDR_IO_IN_PROGRESS(hdr)); */
6242 ASSERT(!HDR_IN_HASH_TABLE(hdr));
6243 ASSERT(!HDR_HAS_L2HDR(hdr));
6244 ASSERT(HDR_EMPTY(hdr));
6245
6246 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
6247 ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
6248 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
6249
6250 hdr->b_l1hdr.b_arc_access = 0;
6251
6252 /*
6253 * If the buf is being overridden then it may already
6254 * have a hdr that is not empty.
6255 */
6256 buf_discard_identity(hdr);
6257 arc_buf_thaw(buf);
6258
6259 return;
6260 }
6261
6262 kmutex_t *hash_lock = HDR_LOCK(hdr);
6263 mutex_enter(hash_lock);
6264
6265 /*
6266 * This assignment is only valid as long as the hash_lock is
6267 * held, we must be careful not to reference state or the
6268 * b_state field after dropping the lock.
6269 */
6270 arc_state_t *state = hdr->b_l1hdr.b_state;
6271 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
6272 ASSERT3P(state, !=, arc_anon);
6273
6274 /* this buffer is not on any list */
6275 ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
6276
6277 if (HDR_HAS_L2HDR(hdr)) {
6278 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
6279
6280 /*
6281 * We have to recheck this conditional again now that
6282 * we're holding the l2ad_mtx to prevent a race with
6283 * another thread which might be concurrently calling
6284 * l2arc_evict(). In that case, l2arc_evict() might have
6285 * destroyed the header's L2 portion as we were waiting
6286 * to acquire the l2ad_mtx.
6287 */
6288 if (HDR_HAS_L2HDR(hdr))
6289 arc_hdr_l2hdr_destroy(hdr);
6290
6291 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
6292 }
6293
6294 /*
6295 * Do we have more than one buf?
6296 */
6297 if (hdr->b_l1hdr.b_bufcnt > 1) {
6298 arc_buf_hdr_t *nhdr;
6299 uint64_t spa = hdr->b_spa;
6300 uint64_t psize = HDR_GET_PSIZE(hdr);
6301 uint64_t lsize = HDR_GET_LSIZE(hdr);
6302 boolean_t protected = HDR_PROTECTED(hdr);
6303 enum zio_compress compress = arc_hdr_get_compress(hdr);
6304 arc_buf_contents_t type = arc_buf_type(hdr);
6305 VERIFY3U(hdr->b_type, ==, type);
6306
6307 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
6308 (void) remove_reference(hdr, hash_lock, tag);
6309
6310 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
6311 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
6312 ASSERT(ARC_BUF_LAST(buf));
6313 }
6314
6315 /*
6316 * Pull the data off of this hdr and attach it to
6317 * a new anonymous hdr. Also find the last buffer
6318 * in the hdr's buffer list.
6319 */
6320 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
6321 ASSERT3P(lastbuf, !=, NULL);
6322
6323 /*
6324 * If the current arc_buf_t and the hdr are sharing their data
6325 * buffer, then we must stop sharing that block.
6326 */
6327 if (arc_buf_is_shared(buf)) {
6328 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
6329 VERIFY(!arc_buf_is_shared(lastbuf));
6330
6331 /*
6332 * First, sever the block sharing relationship between
6333 * buf and the arc_buf_hdr_t.
6334 */
6335 arc_unshare_buf(hdr, buf);
6336
6337 /*
6338 * Now we need to recreate the hdr's b_pabd. Since we
6339 * have lastbuf handy, we try to share with it, but if
6340 * we can't then we allocate a new b_pabd and copy the
6341 * data from buf into it.
6342 */
6343 if (arc_can_share(hdr, lastbuf)) {
6344 arc_share_buf(hdr, lastbuf);
6345 } else {
6346 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT);
6347 abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
6348 buf->b_data, psize);
6349 }
6350 VERIFY3P(lastbuf->b_data, !=, NULL);
6351 } else if (HDR_SHARED_DATA(hdr)) {
6352 /*
6353 * Uncompressed shared buffers are always at the end
6354 * of the list. Compressed buffers don't have the
6355 * same requirements. This makes it hard to
6356 * simply assert that the lastbuf is shared so
6357 * we rely on the hdr's compression flags to determine
6358 * if we have a compressed, shared buffer.
6359 */
6360 ASSERT(arc_buf_is_shared(lastbuf) ||
6361 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
6362 ASSERT(!ARC_BUF_SHARED(buf));
6363 }
6364 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
6365 ASSERT3P(state, !=, arc_l2c_only);
6366
6367 (void) zfs_refcount_remove_many(&state->arcs_size,
6368 arc_buf_size(buf), buf);
6369
6370 if (zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
6371 ASSERT3P(state, !=, arc_l2c_only);
6372 (void) zfs_refcount_remove_many(
6373 &state->arcs_esize[type],
6374 arc_buf_size(buf), buf);
6375 }
6376
6377 hdr->b_l1hdr.b_bufcnt -= 1;
6378 if (ARC_BUF_ENCRYPTED(buf))
6379 hdr->b_crypt_hdr.b_ebufcnt -= 1;
6380
6381 arc_cksum_verify(buf);
6382 arc_buf_unwatch(buf);
6383
6384 /* if this is the last uncompressed buf free the checksum */
6385 if (!arc_hdr_has_uncompressed_buf(hdr))
6386 arc_cksum_free(hdr);
6387
6388 mutex_exit(hash_lock);
6389
6390 /*
6391 * Allocate a new hdr. The new hdr will contain a b_pabd
6392 * buffer which will be freed in arc_write().
6393 */
6394 nhdr = arc_hdr_alloc(spa, psize, lsize, protected,
6395 compress, type, HDR_HAS_RABD(hdr));
6396 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
6397 ASSERT0(nhdr->b_l1hdr.b_bufcnt);
6398 ASSERT0(zfs_refcount_count(&nhdr->b_l1hdr.b_refcnt));
6399 VERIFY3U(nhdr->b_type, ==, type);
6400 ASSERT(!HDR_SHARED_DATA(nhdr));
6401
6402 nhdr->b_l1hdr.b_buf = buf;
6403 nhdr->b_l1hdr.b_bufcnt = 1;
6404 if (ARC_BUF_ENCRYPTED(buf))
6405 nhdr->b_crypt_hdr.b_ebufcnt = 1;
6406 (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
6407 buf->b_hdr = nhdr;
6408
6409 mutex_exit(&buf->b_evict_lock);
6410 (void) zfs_refcount_add_many(&arc_anon->arcs_size,
6411 arc_buf_size(buf), buf);
6412 } else {
6413 mutex_exit(&buf->b_evict_lock);
6414 ASSERT(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
6415 /* protected by hash lock, or hdr is on arc_anon */
6416 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
6417 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6418 arc_change_state(arc_anon, hdr, hash_lock);
6419 hdr->b_l1hdr.b_arc_access = 0;
6420
6421 mutex_exit(hash_lock);
6422 buf_discard_identity(hdr);
6423 arc_buf_thaw(buf);
6424 }
6425 }
6426
6427 int
6428 arc_released(arc_buf_t *buf)
6429 {
6430 int released;
6431
6432 mutex_enter(&buf->b_evict_lock);
6433 released = (buf->b_data != NULL &&
6434 buf->b_hdr->b_l1hdr.b_state == arc_anon);
6435 mutex_exit(&buf->b_evict_lock);
6436 return (released);
6437 }
6438
6439 #ifdef ZFS_DEBUG
6440 int
6441 arc_referenced(arc_buf_t *buf)
6442 {
6443 int referenced;
6444
6445 mutex_enter(&buf->b_evict_lock);
6446 referenced = (zfs_refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
6447 mutex_exit(&buf->b_evict_lock);
6448 return (referenced);
6449 }
6450 #endif
6451
6452 static void
6453 arc_write_ready(zio_t *zio)
6454 {
6455 arc_write_callback_t *callback = zio->io_private;
6456 arc_buf_t *buf = callback->awcb_buf;
6457 arc_buf_hdr_t *hdr = buf->b_hdr;
6458 blkptr_t *bp = zio->io_bp;
6459 uint64_t psize = BP_IS_HOLE(bp) ? 0 : BP_GET_PSIZE(bp);
6460
6461 ASSERT(HDR_HAS_L1HDR(hdr));
6462 ASSERT(!zfs_refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
6463 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
6464
6465 /*
6466 * If we're reexecuting this zio because the pool suspended, then
6467 * cleanup any state that was previously set the first time the
6468 * callback was invoked.
6469 */
6470 if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
6471 arc_cksum_free(hdr);
6472 arc_buf_unwatch(buf);
6473 if (hdr->b_l1hdr.b_pabd != NULL) {
6474 if (arc_buf_is_shared(buf)) {
6475 arc_unshare_buf(hdr, buf);
6476 } else {
6477 arc_hdr_free_pabd(hdr, B_FALSE);
6478 }
6479 }
6480
6481 if (HDR_HAS_RABD(hdr))
6482 arc_hdr_free_pabd(hdr, B_TRUE);
6483 }
6484 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6485 ASSERT(!HDR_HAS_RABD(hdr));
6486 ASSERT(!HDR_SHARED_DATA(hdr));
6487 ASSERT(!arc_buf_is_shared(buf));
6488
6489 callback->awcb_ready(zio, buf, callback->awcb_private);
6490
6491 if (HDR_IO_IN_PROGRESS(hdr))
6492 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
6493
6494 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6495
6496 if (BP_IS_PROTECTED(bp) != !!HDR_PROTECTED(hdr))
6497 hdr = arc_hdr_realloc_crypt(hdr, BP_IS_PROTECTED(bp));
6498
6499 if (BP_IS_PROTECTED(bp)) {
6500 /* ZIL blocks are written through zio_rewrite */
6501 ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG);
6502 ASSERT(HDR_PROTECTED(hdr));
6503
6504 if (BP_SHOULD_BYTESWAP(bp)) {
6505 if (BP_GET_LEVEL(bp) > 0) {
6506 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
6507 } else {
6508 hdr->b_l1hdr.b_byteswap =
6509 DMU_OT_BYTESWAP(BP_GET_TYPE(bp));
6510 }
6511 } else {
6512 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
6513 }
6514
6515 hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp);
6516 hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset;
6517 zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt,
6518 hdr->b_crypt_hdr.b_iv);
6519 zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac);
6520 }
6521
6522 /*
6523 * If this block was written for raw encryption but the zio layer
6524 * ended up only authenticating it, adjust the buffer flags now.
6525 */
6526 if (BP_IS_AUTHENTICATED(bp) && ARC_BUF_ENCRYPTED(buf)) {
6527 arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH);
6528 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
6529 if (BP_GET_COMPRESS(bp) == ZIO_COMPRESS_OFF)
6530 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
6531 } else if (BP_IS_HOLE(bp) && ARC_BUF_ENCRYPTED(buf)) {
6532 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
6533 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
6534 }
6535
6536 /* this must be done after the buffer flags are adjusted */
6537 arc_cksum_compute(buf);
6538
6539 enum zio_compress compress;
6540 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
6541 compress = ZIO_COMPRESS_OFF;
6542 } else {
6543 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
6544 compress = BP_GET_COMPRESS(bp);
6545 }
6546 HDR_SET_PSIZE(hdr, psize);
6547 arc_hdr_set_compress(hdr, compress);
6548
6549 if (zio->io_error != 0 || psize == 0)
6550 goto out;
6551
6552 /*
6553 * Fill the hdr with data. If the buffer is encrypted we have no choice
6554 * but to copy the data into b_rabd. If the hdr is compressed, the data
6555 * we want is available from the zio, otherwise we can take it from
6556 * the buf.
6557 *
6558 * We might be able to share the buf's data with the hdr here. However,
6559 * doing so would cause the ARC to be full of linear ABDs if we write a
6560 * lot of shareable data. As a compromise, we check whether scattered
6561 * ABDs are allowed, and assume that if they are then the user wants
6562 * the ARC to be primarily filled with them regardless of the data being
6563 * written. Therefore, if they're allowed then we allocate one and copy
6564 * the data into it; otherwise, we share the data directly if we can.
6565 */
6566 if (ARC_BUF_ENCRYPTED(buf)) {
6567 ASSERT3U(psize, >, 0);
6568 ASSERT(ARC_BUF_COMPRESSED(buf));
6569 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT|ARC_HDR_ALLOC_RDATA);
6570 abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize);
6571 } else if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) {
6572 /*
6573 * Ideally, we would always copy the io_abd into b_pabd, but the
6574 * user may have disabled compressed ARC, thus we must check the
6575 * hdr's compression setting rather than the io_bp's.
6576 */
6577 if (BP_IS_ENCRYPTED(bp)) {
6578 ASSERT3U(psize, >, 0);
6579 arc_hdr_alloc_pabd(hdr,
6580 ARC_HDR_DO_ADAPT|ARC_HDR_ALLOC_RDATA);
6581 abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize);
6582 } else if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF &&
6583 !ARC_BUF_COMPRESSED(buf)) {
6584 ASSERT3U(psize, >, 0);
6585 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT);
6586 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
6587 } else {
6588 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
6589 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT);
6590 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
6591 arc_buf_size(buf));
6592 }
6593 } else {
6594 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
6595 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
6596 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
6597 arc_share_buf(hdr, buf);
6598 }
6599
6600 out:
6601 arc_hdr_verify(hdr, bp);
6602 }
6603
6604 static void
6605 arc_write_children_ready(zio_t *zio)
6606 {
6607 arc_write_callback_t *callback = zio->io_private;
6608 arc_buf_t *buf = callback->awcb_buf;
6609
6610 callback->awcb_children_ready(zio, buf, callback->awcb_private);
6611 }
6612
6613 /*
6614 * The SPA calls this callback for each physical write that happens on behalf
6615 * of a logical write. See the comment in dbuf_write_physdone() for details.
6616 */
6617 static void
6618 arc_write_physdone(zio_t *zio)
6619 {
6620 arc_write_callback_t *cb = zio->io_private;
6621 if (cb->awcb_physdone != NULL)
6622 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
6623 }
6624
6625 static void
6626 arc_write_done(zio_t *zio)
6627 {
6628 arc_write_callback_t *callback = zio->io_private;
6629 arc_buf_t *buf = callback->awcb_buf;
6630 arc_buf_hdr_t *hdr = buf->b_hdr;
6631
6632 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6633
6634 if (zio->io_error == 0) {
6635 arc_hdr_verify(hdr, zio->io_bp);
6636
6637 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
6638 buf_discard_identity(hdr);
6639 } else {
6640 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
6641 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
6642 }
6643 } else {
6644 ASSERT(HDR_EMPTY(hdr));
6645 }
6646
6647 /*
6648 * If the block to be written was all-zero or compressed enough to be
6649 * embedded in the BP, no write was performed so there will be no
6650 * dva/birth/checksum. The buffer must therefore remain anonymous
6651 * (and uncached).
6652 */
6653 if (!HDR_EMPTY(hdr)) {
6654 arc_buf_hdr_t *exists;
6655 kmutex_t *hash_lock;
6656
6657 ASSERT3U(zio->io_error, ==, 0);
6658
6659 arc_cksum_verify(buf);
6660
6661 exists = buf_hash_insert(hdr, &hash_lock);
6662 if (exists != NULL) {
6663 /*
6664 * This can only happen if we overwrite for
6665 * sync-to-convergence, because we remove
6666 * buffers from the hash table when we arc_free().
6667 */
6668 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
6669 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6670 panic("bad overwrite, hdr=%p exists=%p",
6671 (void *)hdr, (void *)exists);
6672 ASSERT(zfs_refcount_is_zero(
6673 &exists->b_l1hdr.b_refcnt));
6674 arc_change_state(arc_anon, exists, hash_lock);
6675 arc_hdr_destroy(exists);
6676 mutex_exit(hash_lock);
6677 exists = buf_hash_insert(hdr, &hash_lock);
6678 ASSERT3P(exists, ==, NULL);
6679 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
6680 /* nopwrite */
6681 ASSERT(zio->io_prop.zp_nopwrite);
6682 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6683 panic("bad nopwrite, hdr=%p exists=%p",
6684 (void *)hdr, (void *)exists);
6685 } else {
6686 /* Dedup */
6687 ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
6688 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
6689 ASSERT(BP_GET_DEDUP(zio->io_bp));
6690 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
6691 }
6692 }
6693 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6694 /* if it's not anon, we are doing a scrub */
6695 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
6696 arc_access(hdr, hash_lock);
6697 mutex_exit(hash_lock);
6698 } else {
6699 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6700 }
6701
6702 ASSERT(!zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
6703 callback->awcb_done(zio, buf, callback->awcb_private);
6704
6705 abd_put(zio->io_abd);
6706 kmem_free(callback, sizeof (arc_write_callback_t));
6707 }
6708
6709 zio_t *
6710 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
6711 boolean_t l2arc, const zio_prop_t *zp, arc_write_done_func_t *ready,
6712 arc_write_done_func_t *children_ready, arc_write_done_func_t *physdone,
6713 arc_write_done_func_t *done, void *private, zio_priority_t priority,
6714 int zio_flags, const zbookmark_phys_t *zb)
6715 {
6716 arc_buf_hdr_t *hdr = buf->b_hdr;
6717 arc_write_callback_t *callback;
6718 zio_t *zio;
6719 zio_prop_t localprop = *zp;
6720
6721 ASSERT3P(ready, !=, NULL);
6722 ASSERT3P(done, !=, NULL);
6723 ASSERT(!HDR_IO_ERROR(hdr));
6724 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6725 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6726 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
6727 if (l2arc)
6728 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
6729
6730 if (ARC_BUF_ENCRYPTED(buf)) {
6731 ASSERT(ARC_BUF_COMPRESSED(buf));
6732 localprop.zp_encrypt = B_TRUE;
6733 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
6734 /* CONSTCOND */
6735 localprop.zp_byteorder =
6736 (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ?
6737 ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER;
6738 bcopy(hdr->b_crypt_hdr.b_salt, localprop.zp_salt,
6739 ZIO_DATA_SALT_LEN);
6740 bcopy(hdr->b_crypt_hdr.b_iv, localprop.zp_iv,
6741 ZIO_DATA_IV_LEN);
6742 bcopy(hdr->b_crypt_hdr.b_mac, localprop.zp_mac,
6743 ZIO_DATA_MAC_LEN);
6744 if (DMU_OT_IS_ENCRYPTED(localprop.zp_type)) {
6745 localprop.zp_nopwrite = B_FALSE;
6746 localprop.zp_copies =
6747 MIN(localprop.zp_copies, SPA_DVAS_PER_BP - 1);
6748 }
6749 zio_flags |= ZIO_FLAG_RAW;
6750 } else if (ARC_BUF_COMPRESSED(buf)) {
6751 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
6752 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
6753 zio_flags |= ZIO_FLAG_RAW_COMPRESS;
6754 }
6755
6756 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
6757 callback->awcb_ready = ready;
6758 callback->awcb_children_ready = children_ready;
6759 callback->awcb_physdone = physdone;
6760 callback->awcb_done = done;
6761 callback->awcb_private = private;
6762 callback->awcb_buf = buf;
6763
6764 /*
6765 * The hdr's b_pabd is now stale, free it now. A new data block
6766 * will be allocated when the zio pipeline calls arc_write_ready().
6767 */
6768 if (hdr->b_l1hdr.b_pabd != NULL) {
6769 /*
6770 * If the buf is currently sharing the data block with
6771 * the hdr then we need to break that relationship here.
6772 * The hdr will remain with a NULL data pointer and the
6773 * buf will take sole ownership of the block.
6774 */
6775 if (arc_buf_is_shared(buf)) {
6776 arc_unshare_buf(hdr, buf);
6777 } else {
6778 arc_hdr_free_pabd(hdr, B_FALSE);
6779 }
6780 VERIFY3P(buf->b_data, !=, NULL);
6781 }
6782
6783 if (HDR_HAS_RABD(hdr))
6784 arc_hdr_free_pabd(hdr, B_TRUE);
6785
6786 if (!(zio_flags & ZIO_FLAG_RAW))
6787 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
6788
6789 ASSERT(!arc_buf_is_shared(buf));
6790 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6791
6792 zio = zio_write(pio, spa, txg, bp,
6793 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
6794 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
6795 (children_ready != NULL) ? arc_write_children_ready : NULL,
6796 arc_write_physdone, arc_write_done, callback,
6797 priority, zio_flags, zb);
6798
6799 return (zio);
6800 }
6801
6802 static int
6803 arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg)
6804 {
6805 #ifdef _KERNEL
6806 uint64_t available_memory = ptob(freemem);
6807
6808 #if defined(__i386)
6809 available_memory =
6810 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
6811 #endif
6812
6813 if (freemem > physmem * arc_lotsfree_percent / 100)
6814 return (0);
6815
6816 if (txg > spa->spa_lowmem_last_txg) {
6817 spa->spa_lowmem_last_txg = txg;
6818 spa->spa_lowmem_page_load = 0;
6819 }
6820 /*
6821 * If we are in pageout, we know that memory is already tight,
6822 * the arc is already going to be evicting, so we just want to
6823 * continue to let page writes occur as quickly as possible.
6824 */
6825 if (curproc == proc_pageout) {
6826 if (spa->spa_lowmem_page_load >
6827 MAX(ptob(minfree), available_memory) / 4)
6828 return (SET_ERROR(ERESTART));
6829 /* Note: reserve is inflated, so we deflate */
6830 atomic_add_64(&spa->spa_lowmem_page_load, reserve / 8);
6831 return (0);
6832 } else if (spa->spa_lowmem_page_load > 0 && arc_reclaim_needed()) {
6833 /* memory is low, delay before restarting */
6834 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
6835 return (SET_ERROR(EAGAIN));
6836 }
6837 spa->spa_lowmem_page_load = 0;
6838 #endif /* _KERNEL */
6839 return (0);
6840 }
6841
6842 void
6843 arc_tempreserve_clear(uint64_t reserve)
6844 {
6845 atomic_add_64(&arc_tempreserve, -reserve);
6846 ASSERT((int64_t)arc_tempreserve >= 0);
6847 }
6848
6849 int
6850 arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg)
6851 {
6852 int error;
6853 uint64_t anon_size;
6854
6855 if (reserve > arc_c/4 && !arc_no_grow)
6856 arc_c = MIN(arc_c_max, reserve * 4);
6857 if (reserve > arc_c)
6858 return (SET_ERROR(ENOMEM));
6859
6860 /*
6861 * Don't count loaned bufs as in flight dirty data to prevent long
6862 * network delays from blocking transactions that are ready to be
6863 * assigned to a txg.
6864 */
6865
6866 /* assert that it has not wrapped around */
6867 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
6868
6869 anon_size = MAX((int64_t)(zfs_refcount_count(&arc_anon->arcs_size) -
6870 arc_loaned_bytes), 0);
6871
6872 /*
6873 * Writes will, almost always, require additional memory allocations
6874 * in order to compress/encrypt/etc the data. We therefore need to
6875 * make sure that there is sufficient available memory for this.
6876 */
6877 error = arc_memory_throttle(spa, reserve, txg);
6878 if (error != 0)
6879 return (error);
6880
6881 /*
6882 * Throttle writes when the amount of dirty data in the cache
6883 * gets too large. We try to keep the cache less than half full
6884 * of dirty blocks so that our sync times don't grow too large.
6885 *
6886 * In the case of one pool being built on another pool, we want
6887 * to make sure we don't end up throttling the lower (backing)
6888 * pool when the upper pool is the majority contributor to dirty
6889 * data. To insure we make forward progress during throttling, we
6890 * also check the current pool's net dirty data and only throttle
6891 * if it exceeds zfs_arc_pool_dirty_percent of the anonymous dirty
6892 * data in the cache.
6893 *
6894 * Note: if two requests come in concurrently, we might let them
6895 * both succeed, when one of them should fail. Not a huge deal.
6896 */
6897 uint64_t total_dirty = reserve + arc_tempreserve + anon_size;
6898 uint64_t spa_dirty_anon = spa_dirty_data(spa);
6899
6900 if (total_dirty > arc_c * zfs_arc_dirty_limit_percent / 100 &&
6901 anon_size > arc_c * zfs_arc_anon_limit_percent / 100 &&
6902 spa_dirty_anon > anon_size * zfs_arc_pool_dirty_percent / 100) {
6903 uint64_t meta_esize =
6904 zfs_refcount_count(
6905 &arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6906 uint64_t data_esize =
6907 zfs_refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6908 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
6909 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
6910 arc_tempreserve >> 10, meta_esize >> 10,
6911 data_esize >> 10, reserve >> 10, arc_c >> 10);
6912 return (SET_ERROR(ERESTART));
6913 }
6914 atomic_add_64(&arc_tempreserve, reserve);
6915 return (0);
6916 }
6917
6918 static void
6919 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
6920 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
6921 {
6922 size->value.ui64 = zfs_refcount_count(&state->arcs_size);
6923 evict_data->value.ui64 =
6924 zfs_refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
6925 evict_metadata->value.ui64 =
6926 zfs_refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
6927 }
6928
6929 static int
6930 arc_kstat_update(kstat_t *ksp, int rw)
6931 {
6932 arc_stats_t *as = ksp->ks_data;
6933
6934 if (rw == KSTAT_WRITE) {
6935 return (EACCES);
6936 } else {
6937 arc_kstat_update_state(arc_anon,
6938 &as->arcstat_anon_size,
6939 &as->arcstat_anon_evictable_data,
6940 &as->arcstat_anon_evictable_metadata);
6941 arc_kstat_update_state(arc_mru,
6942 &as->arcstat_mru_size,
6943 &as->arcstat_mru_evictable_data,
6944 &as->arcstat_mru_evictable_metadata);
6945 arc_kstat_update_state(arc_mru_ghost,
6946 &as->arcstat_mru_ghost_size,
6947 &as->arcstat_mru_ghost_evictable_data,
6948 &as->arcstat_mru_ghost_evictable_metadata);
6949 arc_kstat_update_state(arc_mfu,
6950 &as->arcstat_mfu_size,
6951 &as->arcstat_mfu_evictable_data,
6952 &as->arcstat_mfu_evictable_metadata);
6953 arc_kstat_update_state(arc_mfu_ghost,
6954 &as->arcstat_mfu_ghost_size,
6955 &as->arcstat_mfu_ghost_evictable_data,
6956 &as->arcstat_mfu_ghost_evictable_metadata);
6957
6958 ARCSTAT(arcstat_size) = aggsum_value(&arc_size);
6959 ARCSTAT(arcstat_meta_used) = aggsum_value(&arc_meta_used);
6960 ARCSTAT(arcstat_data_size) = aggsum_value(&astat_data_size);
6961 ARCSTAT(arcstat_metadata_size) =
6962 aggsum_value(&astat_metadata_size);
6963 ARCSTAT(arcstat_hdr_size) = aggsum_value(&astat_hdr_size);
6964 ARCSTAT(arcstat_other_size) = aggsum_value(&astat_other_size);
6965 ARCSTAT(arcstat_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size);
6966 }
6967
6968 return (0);
6969 }
6970
6971 /*
6972 * This function *must* return indices evenly distributed between all
6973 * sublists of the multilist. This is needed due to how the ARC eviction
6974 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
6975 * distributed between all sublists and uses this assumption when
6976 * deciding which sublist to evict from and how much to evict from it.
6977 */
6978 unsigned int
6979 arc_state_multilist_index_func(multilist_t *ml, void *obj)
6980 {
6981 arc_buf_hdr_t *hdr = obj;
6982
6983 /*
6984 * We rely on b_dva to generate evenly distributed index
6985 * numbers using buf_hash below. So, as an added precaution,
6986 * let's make sure we never add empty buffers to the arc lists.
6987 */
6988 ASSERT(!HDR_EMPTY(hdr));
6989
6990 /*
6991 * The assumption here, is the hash value for a given
6992 * arc_buf_hdr_t will remain constant throughout its lifetime
6993 * (i.e. its b_spa, b_dva, and b_birth fields don't change).
6994 * Thus, we don't need to store the header's sublist index
6995 * on insertion, as this index can be recalculated on removal.
6996 *
6997 * Also, the low order bits of the hash value are thought to be
6998 * distributed evenly. Otherwise, in the case that the multilist
6999 * has a power of two number of sublists, each sublists' usage
7000 * would not be evenly distributed.
7001 */
7002 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
7003 multilist_get_num_sublists(ml));
7004 }
7005
7006 static void
7007 arc_state_init(void)
7008 {
7009 arc_anon = &ARC_anon;
7010 arc_mru = &ARC_mru;
7011 arc_mru_ghost = &ARC_mru_ghost;
7012 arc_mfu = &ARC_mfu;
7013 arc_mfu_ghost = &ARC_mfu_ghost;
7014 arc_l2c_only = &ARC_l2c_only;
7015
7016 arc_mru->arcs_list[ARC_BUFC_METADATA] =
7017 multilist_create(sizeof (arc_buf_hdr_t),
7018 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7019 arc_state_multilist_index_func);
7020 arc_mru->arcs_list[ARC_BUFC_DATA] =
7021 multilist_create(sizeof (arc_buf_hdr_t),
7022 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7023 arc_state_multilist_index_func);
7024 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] =
7025 multilist_create(sizeof (arc_buf_hdr_t),
7026 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7027 arc_state_multilist_index_func);
7028 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] =
7029 multilist_create(sizeof (arc_buf_hdr_t),
7030 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7031 arc_state_multilist_index_func);
7032 arc_mfu->arcs_list[ARC_BUFC_METADATA] =
7033 multilist_create(sizeof (arc_buf_hdr_t),
7034 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7035 arc_state_multilist_index_func);
7036 arc_mfu->arcs_list[ARC_BUFC_DATA] =
7037 multilist_create(sizeof (arc_buf_hdr_t),
7038 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7039 arc_state_multilist_index_func);
7040 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] =
7041 multilist_create(sizeof (arc_buf_hdr_t),
7042 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7043 arc_state_multilist_index_func);
7044 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] =
7045 multilist_create(sizeof (arc_buf_hdr_t),
7046 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7047 arc_state_multilist_index_func);
7048 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] =
7049 multilist_create(sizeof (arc_buf_hdr_t),
7050 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7051 arc_state_multilist_index_func);
7052 arc_l2c_only->arcs_list[ARC_BUFC_DATA] =
7053 multilist_create(sizeof (arc_buf_hdr_t),
7054 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7055 arc_state_multilist_index_func);
7056
7057 zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
7058 zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
7059 zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
7060 zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
7061 zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
7062 zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
7063 zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
7064 zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
7065 zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
7066 zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
7067 zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
7068 zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
7069
7070 zfs_refcount_create(&arc_anon->arcs_size);
7071 zfs_refcount_create(&arc_mru->arcs_size);
7072 zfs_refcount_create(&arc_mru_ghost->arcs_size);
7073 zfs_refcount_create(&arc_mfu->arcs_size);
7074 zfs_refcount_create(&arc_mfu_ghost->arcs_size);
7075 zfs_refcount_create(&arc_l2c_only->arcs_size);
7076
7077 aggsum_init(&arc_meta_used, 0);
7078 aggsum_init(&arc_size, 0);
7079 aggsum_init(&astat_data_size, 0);
7080 aggsum_init(&astat_metadata_size, 0);
7081 aggsum_init(&astat_hdr_size, 0);
7082 aggsum_init(&astat_other_size, 0);
7083 aggsum_init(&astat_l2_hdr_size, 0);
7084
7085 arc_anon->arcs_state = ARC_STATE_ANON;
7086 arc_mru->arcs_state = ARC_STATE_MRU;
7087 arc_mru_ghost->arcs_state = ARC_STATE_MRU_GHOST;
7088 arc_mfu->arcs_state = ARC_STATE_MFU;
7089 arc_mfu_ghost->arcs_state = ARC_STATE_MFU_GHOST;
7090 arc_l2c_only->arcs_state = ARC_STATE_L2C_ONLY;
7091 }
7092
7093 static void
7094 arc_state_fini(void)
7095 {
7096 zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
7097 zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
7098 zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
7099 zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
7100 zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
7101 zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
7102 zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
7103 zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
7104 zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
7105 zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
7106 zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
7107 zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
7108
7109 zfs_refcount_destroy(&arc_anon->arcs_size);
7110 zfs_refcount_destroy(&arc_mru->arcs_size);
7111 zfs_refcount_destroy(&arc_mru_ghost->arcs_size);
7112 zfs_refcount_destroy(&arc_mfu->arcs_size);
7113 zfs_refcount_destroy(&arc_mfu_ghost->arcs_size);
7114 zfs_refcount_destroy(&arc_l2c_only->arcs_size);
7115
7116 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]);
7117 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
7118 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]);
7119 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
7120 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]);
7121 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
7122 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]);
7123 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
7124 multilist_destroy(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]);
7125 multilist_destroy(arc_l2c_only->arcs_list[ARC_BUFC_DATA]);
7126
7127 aggsum_fini(&arc_meta_used);
7128 aggsum_fini(&arc_size);
7129 aggsum_fini(&astat_data_size);
7130 aggsum_fini(&astat_metadata_size);
7131 aggsum_fini(&astat_hdr_size);
7132 aggsum_fini(&astat_other_size);
7133 aggsum_fini(&astat_l2_hdr_size);
7134
7135 }
7136
7137 uint64_t
7138 arc_max_bytes(void)
7139 {
7140 return (arc_c_max);
7141 }
7142
7143 void
7144 arc_init(void)
7145 {
7146 /*
7147 * allmem is "all memory that we could possibly use".
7148 */
7149 #ifdef _KERNEL
7150 uint64_t allmem = ptob(physmem - swapfs_minfree);
7151 #else
7152 uint64_t allmem = (physmem * PAGESIZE) / 2;
7153 #endif
7154 mutex_init(&arc_adjust_lock, NULL, MUTEX_DEFAULT, NULL);
7155 cv_init(&arc_adjust_waiters_cv, NULL, CV_DEFAULT, NULL);
7156
7157 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
7158 arc_c_min = MAX(allmem / 32, 64 << 20);
7159 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
7160 if (allmem >= 1 << 30)
7161 arc_c_max = allmem - (1 << 30);
7162 else
7163 arc_c_max = arc_c_min;
7164 arc_c_max = MAX(allmem * 3 / 4, arc_c_max);
7165
7166 /*
7167 * In userland, there's only the memory pressure that we artificially
7168 * create (see arc_available_memory()). Don't let arc_c get too
7169 * small, because it can cause transactions to be larger than
7170 * arc_c, causing arc_tempreserve_space() to fail.
7171 */
7172 #ifndef _KERNEL
7173 arc_c_min = arc_c_max / 2;
7174 #endif
7175
7176 /*
7177 * Allow the tunables to override our calculations if they are
7178 * reasonable (ie. over 64MB)
7179 */
7180 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) {
7181 arc_c_max = zfs_arc_max;
7182 arc_c_min = MIN(arc_c_min, arc_c_max);
7183 }
7184 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max)
7185 arc_c_min = zfs_arc_min;
7186
7187 arc_c = arc_c_max;
7188 arc_p = (arc_c >> 1);
7189
7190 /* limit meta-data to 1/4 of the arc capacity */
7191 arc_meta_limit = arc_c_max / 4;
7192
7193 #ifdef _KERNEL
7194 /*
7195 * Metadata is stored in the kernel's heap. Don't let us
7196 * use more than half the heap for the ARC.
7197 */
7198 arc_meta_limit = MIN(arc_meta_limit,
7199 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2);
7200 #endif
7201
7202 /* Allow the tunable to override if it is reasonable */
7203 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
7204 arc_meta_limit = zfs_arc_meta_limit;
7205
7206 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
7207 arc_c_min = arc_meta_limit / 2;
7208
7209 /* On larger-memory machines, we clamp the minimum at 1GB */
7210 if (zfs_arc_min == 0)
7211 arc_c_min = MIN(arc_c_min, (1 << 30));
7212
7213 if (zfs_arc_meta_min > 0) {
7214 arc_meta_min = zfs_arc_meta_min;
7215 } else {
7216 arc_meta_min = arc_c_min / 2;
7217 }
7218
7219 if (zfs_arc_grow_retry > 0)
7220 arc_grow_retry = zfs_arc_grow_retry;
7221
7222 if (zfs_arc_shrink_shift > 0)
7223 arc_shrink_shift = zfs_arc_shrink_shift;
7224
7225 /*
7226 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
7227 */
7228 if (arc_no_grow_shift >= arc_shrink_shift)
7229 arc_no_grow_shift = arc_shrink_shift - 1;
7230
7231 if (zfs_arc_p_min_shift > 0)
7232 arc_p_min_shift = zfs_arc_p_min_shift;
7233
7234 /* if kmem_flags are set, lets try to use less memory */
7235 if (kmem_debugging())
7236 arc_c = arc_c / 2;
7237 if (arc_c < arc_c_min)
7238 arc_c = arc_c_min;
7239
7240 arc_state_init();
7241
7242 /*
7243 * The arc must be "uninitialized", so that hdr_recl() (which is
7244 * registered by buf_init()) will not access arc_reap_zthr before
7245 * it is created.
7246 */
7247 ASSERT(!arc_initialized);
7248 buf_init();
7249
7250 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
7251 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
7252
7253 if (arc_ksp != NULL) {
7254 arc_ksp->ks_data = &arc_stats;
7255 arc_ksp->ks_update = arc_kstat_update;
7256 kstat_install(arc_ksp);
7257 }
7258
7259 arc_adjust_zthr = zthr_create(arc_adjust_cb_check,
7260 arc_adjust_cb, NULL);
7261 arc_reap_zthr = zthr_create_timer(arc_reap_cb_check,
7262 arc_reap_cb, NULL, SEC2NSEC(1));
7263
7264 arc_initialized = B_TRUE;
7265 arc_warm = B_FALSE;
7266
7267 /*
7268 * Calculate maximum amount of dirty data per pool.
7269 *
7270 * If it has been set by /etc/system, take that.
7271 * Otherwise, use a percentage of physical memory defined by
7272 * zfs_dirty_data_max_percent (default 10%) with a cap at
7273 * zfs_dirty_data_max_max (default 4GB).
7274 */
7275 if (zfs_dirty_data_max == 0) {
7276 zfs_dirty_data_max = physmem * PAGESIZE *
7277 zfs_dirty_data_max_percent / 100;
7278 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
7279 zfs_dirty_data_max_max);
7280 }
7281 }
7282
7283 void
7284 arc_fini(void)
7285 {
7286 /* Use B_TRUE to ensure *all* buffers are evicted */
7287 arc_flush(NULL, B_TRUE);
7288
7289 arc_initialized = B_FALSE;
7290
7291 if (arc_ksp != NULL) {
7292 kstat_delete(arc_ksp);
7293 arc_ksp = NULL;
7294 }
7295
7296 (void) zthr_cancel(arc_adjust_zthr);
7297 zthr_destroy(arc_adjust_zthr);
7298
7299 (void) zthr_cancel(arc_reap_zthr);
7300 zthr_destroy(arc_reap_zthr);
7301
7302 mutex_destroy(&arc_adjust_lock);
7303 cv_destroy(&arc_adjust_waiters_cv);
7304
7305 /*
7306 * buf_fini() must proceed arc_state_fini() because buf_fin() may
7307 * trigger the release of kmem magazines, which can callback to
7308 * arc_space_return() which accesses aggsums freed in act_state_fini().
7309 */
7310 buf_fini();
7311 arc_state_fini();
7312
7313 ASSERT0(arc_loaned_bytes);
7314 }
7315
7316 /*
7317 * Level 2 ARC
7318 *
7319 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
7320 * It uses dedicated storage devices to hold cached data, which are populated
7321 * using large infrequent writes. The main role of this cache is to boost
7322 * the performance of random read workloads. The intended L2ARC devices
7323 * include short-stroked disks, solid state disks, and other media with
7324 * substantially faster read latency than disk.
7325 *
7326 * +-----------------------+
7327 * | ARC |
7328 * +-----------------------+
7329 * | ^ ^
7330 * | | |
7331 * l2arc_feed_thread() arc_read()
7332 * | | |
7333 * | l2arc read |
7334 * V | |
7335 * +---------------+ |
7336 * | L2ARC | |
7337 * +---------------+ |
7338 * | ^ |
7339 * l2arc_write() | |
7340 * | | |
7341 * V | |
7342 * +-------+ +-------+
7343 * | vdev | | vdev |
7344 * | cache | | cache |
7345 * +-------+ +-------+
7346 * +=========+ .-----.
7347 * : L2ARC : |-_____-|
7348 * : devices : | Disks |
7349 * +=========+ `-_____-'
7350 *
7351 * Read requests are satisfied from the following sources, in order:
7352 *
7353 * 1) ARC
7354 * 2) vdev cache of L2ARC devices
7355 * 3) L2ARC devices
7356 * 4) vdev cache of disks
7357 * 5) disks
7358 *
7359 * Some L2ARC device types exhibit extremely slow write performance.
7360 * To accommodate for this there are some significant differences between
7361 * the L2ARC and traditional cache design:
7362 *
7363 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
7364 * the ARC behave as usual, freeing buffers and placing headers on ghost
7365 * lists. The ARC does not send buffers to the L2ARC during eviction as
7366 * this would add inflated write latencies for all ARC memory pressure.
7367 *
7368 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
7369 * It does this by periodically scanning buffers from the eviction-end of
7370 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
7371 * not already there. It scans until a headroom of buffers is satisfied,
7372 * which itself is a buffer for ARC eviction. If a compressible buffer is
7373 * found during scanning and selected for writing to an L2ARC device, we
7374 * temporarily boost scanning headroom during the next scan cycle to make
7375 * sure we adapt to compression effects (which might significantly reduce
7376 * the data volume we write to L2ARC). The thread that does this is
7377 * l2arc_feed_thread(), illustrated below; example sizes are included to
7378 * provide a better sense of ratio than this diagram:
7379 *
7380 * head --> tail
7381 * +---------------------+----------+
7382 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
7383 * +---------------------+----------+ | o L2ARC eligible
7384 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
7385 * +---------------------+----------+ |
7386 * 15.9 Gbytes ^ 32 Mbytes |
7387 * headroom |
7388 * l2arc_feed_thread()
7389 * |
7390 * l2arc write hand <--[oooo]--'
7391 * | 8 Mbyte
7392 * | write max
7393 * V
7394 * +==============================+
7395 * L2ARC dev |####|#|###|###| |####| ... |
7396 * +==============================+
7397 * 32 Gbytes
7398 *
7399 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
7400 * evicted, then the L2ARC has cached a buffer much sooner than it probably
7401 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
7402 * safe to say that this is an uncommon case, since buffers at the end of
7403 * the ARC lists have moved there due to inactivity.
7404 *
7405 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
7406 * then the L2ARC simply misses copying some buffers. This serves as a
7407 * pressure valve to prevent heavy read workloads from both stalling the ARC
7408 * with waits and clogging the L2ARC with writes. This also helps prevent
7409 * the potential for the L2ARC to churn if it attempts to cache content too
7410 * quickly, such as during backups of the entire pool.
7411 *
7412 * 5. After system boot and before the ARC has filled main memory, there are
7413 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
7414 * lists can remain mostly static. Instead of searching from tail of these
7415 * lists as pictured, the l2arc_feed_thread() will search from the list heads
7416 * for eligible buffers, greatly increasing its chance of finding them.
7417 *
7418 * The L2ARC device write speed is also boosted during this time so that
7419 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
7420 * there are no L2ARC reads, and no fear of degrading read performance
7421 * through increased writes.
7422 *
7423 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
7424 * the vdev queue can aggregate them into larger and fewer writes. Each
7425 * device is written to in a rotor fashion, sweeping writes through
7426 * available space then repeating.
7427 *
7428 * 7. The L2ARC does not store dirty content. It never needs to flush
7429 * write buffers back to disk based storage.
7430 *
7431 * 8. If an ARC buffer is written (and dirtied) which also exists in the
7432 * L2ARC, the now stale L2ARC buffer is immediately dropped.
7433 *
7434 * The performance of the L2ARC can be tweaked by a number of tunables, which
7435 * may be necessary for different workloads:
7436 *
7437 * l2arc_write_max max write bytes per interval
7438 * l2arc_write_boost extra write bytes during device warmup
7439 * l2arc_noprefetch skip caching prefetched buffers
7440 * l2arc_headroom number of max device writes to precache
7441 * l2arc_headroom_boost when we find compressed buffers during ARC
7442 * scanning, we multiply headroom by this
7443 * percentage factor for the next scan cycle,
7444 * since more compressed buffers are likely to
7445 * be present
7446 * l2arc_feed_secs seconds between L2ARC writing
7447 *
7448 * Tunables may be removed or added as future performance improvements are
7449 * integrated, and also may become zpool properties.
7450 *
7451 * There are three key functions that control how the L2ARC warms up:
7452 *
7453 * l2arc_write_eligible() check if a buffer is eligible to cache
7454 * l2arc_write_size() calculate how much to write
7455 * l2arc_write_interval() calculate sleep delay between writes
7456 *
7457 * These three functions determine what to write, how much, and how quickly
7458 * to send writes.
7459 *
7460 * L2ARC persistence:
7461 *
7462 * When writing buffers to L2ARC, we periodically add some metadata to
7463 * make sure we can pick them up after reboot, thus dramatically reducing
7464 * the impact that any downtime has on the performance of storage systems
7465 * with large caches.
7466 *
7467 * The implementation works fairly simply by integrating the following two
7468 * modifications:
7469 *
7470 * *) When writing to the L2ARC, we occasionally write a "l2arc log block",
7471 * which is an additional piece of metadata which describes what's been
7472 * written. This allows us to rebuild the arc_buf_hdr_t structures of the
7473 * main ARC buffers. There are 2 linked-lists of log blocks headed by
7474 * dh_start_lbps[2]. We alternate which chain we append to, so they are
7475 * time-wise and offset-wise interleaved, but that is an optimization rather
7476 * than for correctness. The log block also includes a pointer to the
7477 * previous block in its chain.
7478 *
7479 * *) We reserve SPA_MINBLOCKSIZE of space at the start of each L2ARC device
7480 * for our header bookkeeping purposes. This contains a device header,
7481 * which contains our top-level reference structures. We update it each
7482 * time we write a new log block, so that we're able to locate it in the
7483 * L2ARC device. If this write results in an inconsistent device header
7484 * (e.g. due to power failure), we detect this by verifying the header's
7485 * checksum and simply fail to reconstruct the L2ARC after reboot.
7486 *
7487 * Implementation diagram:
7488 *
7489 * +=== L2ARC device (not to scale) ======================================+
7490 * | ___two newest log block pointers__.__________ |
7491 * | / \dh_start_lbps[1] |
7492 * | / \ \dh_start_lbps[0]|
7493 * |.___/__. V V |
7494 * ||L2 dev|....|lb |bufs |lb |bufs |lb |bufs |lb |bufs |lb |---(empty)---|
7495 * || hdr| ^ /^ /^ / / |
7496 * |+------+ ...--\-------/ \-----/--\------/ / |
7497 * | \--------------/ \--------------/ |
7498 * +======================================================================+
7499 *
7500 * As can be seen on the diagram, rather than using a simple linked list,
7501 * we use a pair of linked lists with alternating elements. This is a
7502 * performance enhancement due to the fact that we only find out the
7503 * address of the next log block access once the current block has been
7504 * completely read in. Obviously, this hurts performance, because we'd be
7505 * keeping the device's I/O queue at only a 1 operation deep, thus
7506 * incurring a large amount of I/O round-trip latency. Having two lists
7507 * allows us to fetch two log blocks ahead of where we are currently
7508 * rebuilding L2ARC buffers.
7509 *
7510 * On-device data structures:
7511 *
7512 * L2ARC device header: l2arc_dev_hdr_phys_t
7513 * L2ARC log block: l2arc_log_blk_phys_t
7514 *
7515 * L2ARC reconstruction:
7516 *
7517 * When writing data, we simply write in the standard rotary fashion,
7518 * evicting buffers as we go and simply writing new data over them (writing
7519 * a new log block every now and then). This obviously means that once we
7520 * loop around the end of the device, we will start cutting into an already
7521 * committed log block (and its referenced data buffers), like so:
7522 *
7523 * current write head__ __old tail
7524 * \ /
7525 * V V
7526 * <--|bufs |lb |bufs |lb | |bufs |lb |bufs |lb |-->
7527 * ^ ^^^^^^^^^___________________________________
7528 * | \
7529 * <<nextwrite>> may overwrite this blk and/or its bufs --'
7530 *
7531 * When importing the pool, we detect this situation and use it to stop
7532 * our scanning process (see l2arc_rebuild).
7533 *
7534 * There is one significant caveat to consider when rebuilding ARC contents
7535 * from an L2ARC device: what about invalidated buffers? Given the above
7536 * construction, we cannot update blocks which we've already written to amend
7537 * them to remove buffers which were invalidated. Thus, during reconstruction,
7538 * we might be populating the cache with buffers for data that's not on the
7539 * main pool anymore, or may have been overwritten!
7540 *
7541 * As it turns out, this isn't a problem. Every arc_read request includes
7542 * both the DVA and, crucially, the birth TXG of the BP the caller is
7543 * looking for. So even if the cache were populated by completely rotten
7544 * blocks for data that had been long deleted and/or overwritten, we'll
7545 * never actually return bad data from the cache, since the DVA with the
7546 * birth TXG uniquely identify a block in space and time - once created,
7547 * a block is immutable on disk. The worst thing we have done is wasted
7548 * some time and memory at l2arc rebuild to reconstruct outdated ARC
7549 * entries that will get dropped from the l2arc as it is being updated
7550 * with new blocks.
7551 *
7552 * L2ARC buffers that have been evicted by l2arc_evict() ahead of the write
7553 * hand are not restored. This is done by saving the offset (in bytes)
7554 * l2arc_evict() has evicted to in the L2ARC device header and taking it
7555 * into account when restoring buffers.
7556 */
7557
7558 static boolean_t
7559 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
7560 {
7561 /*
7562 * A buffer is *not* eligible for the L2ARC if it:
7563 * 1. belongs to a different spa.
7564 * 2. is already cached on the L2ARC.
7565 * 3. has an I/O in progress (it may be an incomplete read).
7566 * 4. is flagged not eligible (zfs property).
7567 * 5. is a prefetch and l2arc_noprefetch is set.
7568 */
7569 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
7570 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr) ||
7571 (l2arc_noprefetch && HDR_PREFETCH(hdr)))
7572 return (B_FALSE);
7573
7574 return (B_TRUE);
7575 }
7576
7577 static uint64_t
7578 l2arc_write_size(l2arc_dev_t *dev)
7579 {
7580 uint64_t size, dev_size;
7581
7582 /*
7583 * Make sure our globals have meaningful values in case the user
7584 * altered them.
7585 */
7586 size = l2arc_write_max;
7587 if (size == 0) {
7588 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
7589 "be greater than zero, resetting it to the default (%d)",
7590 L2ARC_WRITE_SIZE);
7591 size = l2arc_write_max = L2ARC_WRITE_SIZE;
7592 }
7593
7594 if (arc_warm == B_FALSE)
7595 size += l2arc_write_boost;
7596
7597 /*
7598 * Make sure the write size does not exceed the size of the cache
7599 * device. This is important in l2arc_evict(), otherwise infinite
7600 * iteration can occur.
7601 */
7602 dev_size = dev->l2ad_end - dev->l2ad_start;
7603 if ((size + l2arc_log_blk_overhead(size, dev)) >= dev_size) {
7604 cmn_err(CE_NOTE, "l2arc_write_max or l2arc_write_boost "
7605 "plus the overhead of log blocks (persistent L2ARC, "
7606 "%" PRIu64 " bytes) exceeds the size of the cache device "
7607 "(guid %" PRIu64 "), resetting them to the default (%d)",
7608 l2arc_log_blk_overhead(size, dev),
7609 dev->l2ad_vdev->vdev_guid, L2ARC_WRITE_SIZE);
7610 size = l2arc_write_max = l2arc_write_boost = L2ARC_WRITE_SIZE;
7611
7612 if (arc_warm == B_FALSE)
7613 size += l2arc_write_boost;
7614 }
7615
7616 return (size);
7617
7618 }
7619
7620 static clock_t
7621 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
7622 {
7623 clock_t interval, next, now;
7624
7625 /*
7626 * If the ARC lists are busy, increase our write rate; if the
7627 * lists are stale, idle back. This is achieved by checking
7628 * how much we previously wrote - if it was more than half of
7629 * what we wanted, schedule the next write much sooner.
7630 */
7631 if (l2arc_feed_again && wrote > (wanted / 2))
7632 interval = (hz * l2arc_feed_min_ms) / 1000;
7633 else
7634 interval = hz * l2arc_feed_secs;
7635
7636 now = ddi_get_lbolt();
7637 next = MAX(now, MIN(now + interval, began + interval));
7638
7639 return (next);
7640 }
7641
7642 /*
7643 * Cycle through L2ARC devices. This is how L2ARC load balances.
7644 * If a device is returned, this also returns holding the spa config lock.
7645 */
7646 static l2arc_dev_t *
7647 l2arc_dev_get_next(void)
7648 {
7649 l2arc_dev_t *first, *next = NULL;
7650
7651 /*
7652 * Lock out the removal of spas (spa_namespace_lock), then removal
7653 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
7654 * both locks will be dropped and a spa config lock held instead.
7655 */
7656 mutex_enter(&spa_namespace_lock);
7657 mutex_enter(&l2arc_dev_mtx);
7658
7659 /* if there are no vdevs, there is nothing to do */
7660 if (l2arc_ndev == 0)
7661 goto out;
7662
7663 first = NULL;
7664 next = l2arc_dev_last;
7665 do {
7666 /* loop around the list looking for a non-faulted vdev */
7667 if (next == NULL) {
7668 next = list_head(l2arc_dev_list);
7669 } else {
7670 next = list_next(l2arc_dev_list, next);
7671 if (next == NULL)
7672 next = list_head(l2arc_dev_list);
7673 }
7674
7675 /* if we have come back to the start, bail out */
7676 if (first == NULL)
7677 first = next;
7678 else if (next == first)
7679 break;
7680
7681 } while (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild);
7682
7683 /* if we were unable to find any usable vdevs, return NULL */
7684 if (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild)
7685 next = NULL;
7686
7687 l2arc_dev_last = next;
7688
7689 out:
7690 mutex_exit(&l2arc_dev_mtx);
7691
7692 /*
7693 * Grab the config lock to prevent the 'next' device from being
7694 * removed while we are writing to it.
7695 */
7696 if (next != NULL)
7697 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
7698 mutex_exit(&spa_namespace_lock);
7699
7700 return (next);
7701 }
7702
7703 /*
7704 * Free buffers that were tagged for destruction.
7705 */
7706 static void
7707 l2arc_do_free_on_write()
7708 {
7709 list_t *buflist;
7710 l2arc_data_free_t *df, *df_prev;
7711
7712 mutex_enter(&l2arc_free_on_write_mtx);
7713 buflist = l2arc_free_on_write;
7714
7715 for (df = list_tail(buflist); df; df = df_prev) {
7716 df_prev = list_prev(buflist, df);
7717 ASSERT3P(df->l2df_abd, !=, NULL);
7718 abd_free(df->l2df_abd);
7719 list_remove(buflist, df);
7720 kmem_free(df, sizeof (l2arc_data_free_t));
7721 }
7722
7723 mutex_exit(&l2arc_free_on_write_mtx);
7724 }
7725
7726 /*
7727 * A write to a cache device has completed. Update all headers to allow
7728 * reads from these buffers to begin.
7729 */
7730 static void
7731 l2arc_write_done(zio_t *zio)
7732 {
7733 l2arc_write_callback_t *cb;
7734 l2arc_lb_abd_buf_t *abd_buf;
7735 l2arc_lb_ptr_buf_t *lb_ptr_buf;
7736 l2arc_dev_t *dev;
7737 l2arc_dev_hdr_phys_t *l2dhdr;
7738 list_t *buflist;
7739 arc_buf_hdr_t *head, *hdr, *hdr_prev;
7740 kmutex_t *hash_lock;
7741 int64_t bytes_dropped = 0;
7742
7743 cb = zio->io_private;
7744 ASSERT3P(cb, !=, NULL);
7745 dev = cb->l2wcb_dev;
7746 l2dhdr = dev->l2ad_dev_hdr;
7747 ASSERT3P(dev, !=, NULL);
7748 head = cb->l2wcb_head;
7749 ASSERT3P(head, !=, NULL);
7750 buflist = &dev->l2ad_buflist;
7751 ASSERT3P(buflist, !=, NULL);
7752 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
7753 l2arc_write_callback_t *, cb);
7754
7755 /*
7756 * All writes completed, or an error was hit.
7757 */
7758 top:
7759 mutex_enter(&dev->l2ad_mtx);
7760 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
7761 hdr_prev = list_prev(buflist, hdr);
7762
7763 hash_lock = HDR_LOCK(hdr);
7764
7765 /*
7766 * We cannot use mutex_enter or else we can deadlock
7767 * with l2arc_write_buffers (due to swapping the order
7768 * the hash lock and l2ad_mtx are taken).
7769 */
7770 if (!mutex_tryenter(hash_lock)) {
7771 /*
7772 * Missed the hash lock. We must retry so we
7773 * don't leave the ARC_FLAG_L2_WRITING bit set.
7774 */
7775 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
7776
7777 /*
7778 * We don't want to rescan the headers we've
7779 * already marked as having been written out, so
7780 * we reinsert the head node so we can pick up
7781 * where we left off.
7782 */
7783 list_remove(buflist, head);
7784 list_insert_after(buflist, hdr, head);
7785
7786 mutex_exit(&dev->l2ad_mtx);
7787
7788 /*
7789 * We wait for the hash lock to become available
7790 * to try and prevent busy waiting, and increase
7791 * the chance we'll be able to acquire the lock
7792 * the next time around.
7793 */
7794 mutex_enter(hash_lock);
7795 mutex_exit(hash_lock);
7796 goto top;
7797 }
7798
7799 /*
7800 * We could not have been moved into the arc_l2c_only
7801 * state while in-flight due to our ARC_FLAG_L2_WRITING
7802 * bit being set. Let's just ensure that's being enforced.
7803 */
7804 ASSERT(HDR_HAS_L1HDR(hdr));
7805
7806 if (zio->io_error != 0) {
7807 /*
7808 * Error - drop L2ARC entry.
7809 */
7810 list_remove(buflist, hdr);
7811 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
7812
7813 uint64_t psize = HDR_GET_PSIZE(hdr);
7814 l2arc_hdr_arcstats_decrement(hdr);
7815
7816 bytes_dropped +=
7817 vdev_psize_to_asize(dev->l2ad_vdev, psize);
7818 (void) zfs_refcount_remove_many(&dev->l2ad_alloc,
7819 arc_hdr_size(hdr), hdr);
7820 }
7821
7822 /*
7823 * Allow ARC to begin reads and ghost list evictions to
7824 * this L2ARC entry.
7825 */
7826 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
7827
7828 mutex_exit(hash_lock);
7829 }
7830
7831 /*
7832 * Free the allocated abd buffers for writing the log blocks.
7833 * If the zio failed reclaim the allocated space and remove the
7834 * pointers to these log blocks from the log block pointer list
7835 * of the L2ARC device.
7836 */
7837 while ((abd_buf = list_remove_tail(&cb->l2wcb_abd_list)) != NULL) {
7838 abd_free(abd_buf->abd);
7839 zio_buf_free(abd_buf, sizeof (*abd_buf));
7840 if (zio->io_error != 0) {
7841 lb_ptr_buf = list_remove_head(&dev->l2ad_lbptr_list);
7842 /*
7843 * L2BLK_GET_PSIZE returns aligned size for log
7844 * blocks.
7845 */
7846 uint64_t asize =
7847 L2BLK_GET_PSIZE((lb_ptr_buf->lb_ptr)->lbp_prop);
7848 bytes_dropped += asize;
7849 ARCSTAT_INCR(arcstat_l2_log_blk_asize, -asize);
7850 ARCSTAT_BUMPDOWN(arcstat_l2_log_blk_count);
7851 zfs_refcount_remove_many(&dev->l2ad_lb_asize, asize,
7852 lb_ptr_buf);
7853 zfs_refcount_remove(&dev->l2ad_lb_count, lb_ptr_buf);
7854 kmem_free(lb_ptr_buf->lb_ptr,
7855 sizeof (l2arc_log_blkptr_t));
7856 kmem_free(lb_ptr_buf, sizeof (l2arc_lb_ptr_buf_t));
7857 }
7858 }
7859 list_destroy(&cb->l2wcb_abd_list);
7860
7861 if (zio->io_error != 0) {
7862 ARCSTAT_BUMP(arcstat_l2_writes_error);
7863
7864 /*
7865 * Restore the lbps array in the header to its previous state.
7866 * If the list of log block pointers is empty, zero out the
7867 * log block pointers in the device header.
7868 */
7869 lb_ptr_buf = list_head(&dev->l2ad_lbptr_list);
7870 for (int i = 0; i < 2; i++) {
7871 if (lb_ptr_buf == NULL) {
7872 /*
7873 * If the list is empty zero out the device
7874 * header. Otherwise zero out the second log
7875 * block pointer in the header.
7876 */
7877 if (i == 0) {
7878 bzero(l2dhdr, dev->l2ad_dev_hdr_asize);
7879 } else {
7880 bzero(&l2dhdr->dh_start_lbps[i],
7881 sizeof (l2arc_log_blkptr_t));
7882 }
7883 break;
7884 }
7885 bcopy(lb_ptr_buf->lb_ptr, &l2dhdr->dh_start_lbps[i],
7886 sizeof (l2arc_log_blkptr_t));
7887 lb_ptr_buf = list_next(&dev->l2ad_lbptr_list,
7888 lb_ptr_buf);
7889 }
7890 }
7891
7892 atomic_inc_64(&l2arc_writes_done);
7893 list_remove(buflist, head);
7894 ASSERT(!HDR_HAS_L1HDR(head));
7895 kmem_cache_free(hdr_l2only_cache, head);
7896 mutex_exit(&dev->l2ad_mtx);
7897
7898 ASSERT(dev->l2ad_vdev != NULL);
7899 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
7900
7901 l2arc_do_free_on_write();
7902
7903 kmem_free(cb, sizeof (l2arc_write_callback_t));
7904 }
7905
7906 static int
7907 l2arc_untransform(zio_t *zio, l2arc_read_callback_t *cb)
7908 {
7909 int ret;
7910 spa_t *spa = zio->io_spa;
7911 arc_buf_hdr_t *hdr = cb->l2rcb_hdr;
7912 blkptr_t *bp = zio->io_bp;
7913 uint8_t salt[ZIO_DATA_SALT_LEN];
7914 uint8_t iv[ZIO_DATA_IV_LEN];
7915 uint8_t mac[ZIO_DATA_MAC_LEN];
7916 boolean_t no_crypt = B_FALSE;
7917
7918 /*
7919 * ZIL data is never be written to the L2ARC, so we don't need
7920 * special handling for its unique MAC storage.
7921 */
7922 ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG);
7923 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
7924 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
7925
7926 /*
7927 * If the data was encrypted, decrypt it now. Note that
7928 * we must check the bp here and not the hdr, since the
7929 * hdr does not have its encryption parameters updated
7930 * until arc_read_done().
7931 */
7932 if (BP_IS_ENCRYPTED(bp)) {
7933 abd_t *eabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr,
7934 B_TRUE);
7935
7936 zio_crypt_decode_params_bp(bp, salt, iv);
7937 zio_crypt_decode_mac_bp(bp, mac);
7938
7939 ret = spa_do_crypt_abd(B_FALSE, spa, &cb->l2rcb_zb,
7940 BP_GET_TYPE(bp), BP_GET_DEDUP(bp), BP_SHOULD_BYTESWAP(bp),
7941 salt, iv, mac, HDR_GET_PSIZE(hdr), eabd,
7942 hdr->b_l1hdr.b_pabd, &no_crypt);
7943 if (ret != 0) {
7944 arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr);
7945 goto error;
7946 }
7947
7948 /*
7949 * If we actually performed decryption, replace b_pabd
7950 * with the decrypted data. Otherwise we can just throw
7951 * our decryption buffer away.
7952 */
7953 if (!no_crypt) {
7954 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
7955 arc_hdr_size(hdr), hdr);
7956 hdr->b_l1hdr.b_pabd = eabd;
7957 zio->io_abd = eabd;
7958 } else {
7959 arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr);
7960 }
7961 }
7962
7963 /*
7964 * If the L2ARC block was compressed, but ARC compression
7965 * is disabled we decompress the data into a new buffer and
7966 * replace the existing data.
7967 */
7968 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
7969 !HDR_COMPRESSION_ENABLED(hdr)) {
7970 abd_t *cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr,
7971 B_TRUE);
7972 void *tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr));
7973
7974 ret = zio_decompress_data(HDR_GET_COMPRESS(hdr),
7975 hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr),
7976 HDR_GET_LSIZE(hdr));
7977 if (ret != 0) {
7978 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
7979 arc_free_data_abd(hdr, cabd, arc_hdr_size(hdr), hdr);
7980 goto error;
7981 }
7982
7983 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
7984 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
7985 arc_hdr_size(hdr), hdr);
7986 hdr->b_l1hdr.b_pabd = cabd;
7987 zio->io_abd = cabd;
7988 zio->io_size = HDR_GET_LSIZE(hdr);
7989 }
7990
7991 return (0);
7992
7993 error:
7994 return (ret);
7995 }
7996
7997
7998 /*
7999 * A read to a cache device completed. Validate buffer contents before
8000 * handing over to the regular ARC routines.
8001 */
8002 static void
8003 l2arc_read_done(zio_t *zio)
8004 {
8005 int tfm_error = 0;
8006 l2arc_read_callback_t *cb = zio->io_private;
8007 arc_buf_hdr_t *hdr;
8008 kmutex_t *hash_lock;
8009 boolean_t valid_cksum;
8010 boolean_t using_rdata = (BP_IS_ENCRYPTED(&cb->l2rcb_bp) &&
8011 (cb->l2rcb_flags & ZIO_FLAG_RAW_ENCRYPT));
8012
8013 ASSERT3P(zio->io_vd, !=, NULL);
8014 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
8015
8016 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
8017
8018 ASSERT3P(cb, !=, NULL);
8019 hdr = cb->l2rcb_hdr;
8020 ASSERT3P(hdr, !=, NULL);
8021
8022 hash_lock = HDR_LOCK(hdr);
8023 mutex_enter(hash_lock);
8024 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
8025
8026 /*
8027 * If the data was read into a temporary buffer,
8028 * move it and free the buffer.
8029 */
8030 if (cb->l2rcb_abd != NULL) {
8031 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
8032 if (zio->io_error == 0) {
8033 if (using_rdata) {
8034 abd_copy(hdr->b_crypt_hdr.b_rabd,
8035 cb->l2rcb_abd, arc_hdr_size(hdr));
8036 } else {
8037 abd_copy(hdr->b_l1hdr.b_pabd,
8038 cb->l2rcb_abd, arc_hdr_size(hdr));
8039 }
8040 }
8041
8042 /*
8043 * The following must be done regardless of whether
8044 * there was an error:
8045 * - free the temporary buffer
8046 * - point zio to the real ARC buffer
8047 * - set zio size accordingly
8048 * These are required because zio is either re-used for
8049 * an I/O of the block in the case of the error
8050 * or the zio is passed to arc_read_done() and it
8051 * needs real data.
8052 */
8053 abd_free(cb->l2rcb_abd);
8054 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
8055
8056 if (using_rdata) {
8057 ASSERT(HDR_HAS_RABD(hdr));
8058 zio->io_abd = zio->io_orig_abd =
8059 hdr->b_crypt_hdr.b_rabd;
8060 } else {
8061 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
8062 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
8063 }
8064 }
8065
8066 ASSERT3P(zio->io_abd, !=, NULL);
8067
8068 /*
8069 * Check this survived the L2ARC journey.
8070 */
8071 ASSERT(zio->io_abd == hdr->b_l1hdr.b_pabd ||
8072 (HDR_HAS_RABD(hdr) && zio->io_abd == hdr->b_crypt_hdr.b_rabd));
8073 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
8074 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
8075
8076 valid_cksum = arc_cksum_is_equal(hdr, zio);
8077
8078 /*
8079 * b_rabd will always match the data as it exists on disk if it is
8080 * being used. Therefore if we are reading into b_rabd we do not
8081 * attempt to untransform the data.
8082 */
8083 if (valid_cksum && !using_rdata)
8084 tfm_error = l2arc_untransform(zio, cb);
8085
8086 if (valid_cksum && tfm_error == 0 && zio->io_error == 0 &&
8087 !HDR_L2_EVICTED(hdr)) {
8088 mutex_exit(hash_lock);
8089 zio->io_private = hdr;
8090 arc_read_done(zio);
8091 } else {
8092 /*
8093 * Buffer didn't survive caching. Increment stats and
8094 * reissue to the original storage device.
8095 */
8096 if (zio->io_error != 0) {
8097 ARCSTAT_BUMP(arcstat_l2_io_error);
8098 } else {
8099 zio->io_error = SET_ERROR(EIO);
8100 }
8101 if (!valid_cksum || tfm_error != 0)
8102 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
8103
8104 /*
8105 * If there's no waiter, issue an async i/o to the primary
8106 * storage now. If there *is* a waiter, the caller must
8107 * issue the i/o in a context where it's OK to block.
8108 */
8109 if (zio->io_waiter == NULL) {
8110 zio_t *pio = zio_unique_parent(zio);
8111 void *abd = (using_rdata) ?
8112 hdr->b_crypt_hdr.b_rabd : hdr->b_l1hdr.b_pabd;
8113
8114 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
8115
8116 zio = zio_read(pio, zio->io_spa, zio->io_bp,
8117 abd, zio->io_size, arc_read_done,
8118 hdr, zio->io_priority, cb->l2rcb_flags,
8119 &cb->l2rcb_zb);
8120
8121 /*
8122 * Original ZIO will be freed, so we need to update
8123 * ARC header with the new ZIO pointer to be used
8124 * by zio_change_priority() in arc_read().
8125 */
8126 for (struct arc_callback *acb = hdr->b_l1hdr.b_acb;
8127 acb != NULL; acb = acb->acb_next)
8128 acb->acb_zio_head = zio;
8129
8130 mutex_exit(hash_lock);
8131 zio_nowait(zio);
8132 } else {
8133 mutex_exit(hash_lock);
8134 }
8135 }
8136
8137 kmem_free(cb, sizeof (l2arc_read_callback_t));
8138 }
8139
8140 /*
8141 * This is the list priority from which the L2ARC will search for pages to
8142 * cache. This is used within loops (0..3) to cycle through lists in the
8143 * desired order. This order can have a significant effect on cache
8144 * performance.
8145 *
8146 * Currently the metadata lists are hit first, MFU then MRU, followed by
8147 * the data lists. This function returns a locked list, and also returns
8148 * the lock pointer.
8149 */
8150 static multilist_sublist_t *
8151 l2arc_sublist_lock(int list_num)
8152 {
8153 multilist_t *ml = NULL;
8154 unsigned int idx;
8155
8156 ASSERT(list_num >= 0 && list_num < L2ARC_FEED_TYPES);
8157
8158 switch (list_num) {
8159 case 0:
8160 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
8161 break;
8162 case 1:
8163 ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
8164 break;
8165 case 2:
8166 ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
8167 break;
8168 case 3:
8169 ml = arc_mru->arcs_list[ARC_BUFC_DATA];
8170 break;
8171 default:
8172 return (NULL);
8173 }
8174
8175 /*
8176 * Return a randomly-selected sublist. This is acceptable
8177 * because the caller feeds only a little bit of data for each
8178 * call (8MB). Subsequent calls will result in different
8179 * sublists being selected.
8180 */
8181 idx = multilist_get_random_index(ml);
8182 return (multilist_sublist_lock(ml, idx));
8183 }
8184
8185 /*
8186 * Calculates the maximum overhead of L2ARC metadata log blocks for a given
8187 * L2ARC write size. l2arc_evict and l2arc_write_size need to include this
8188 * overhead in processing to make sure there is enough headroom available
8189 * when writing buffers.
8190 */
8191 static inline uint64_t
8192 l2arc_log_blk_overhead(uint64_t write_sz, l2arc_dev_t *dev)
8193 {
8194 if (dev->l2ad_log_entries == 0) {
8195 return (0);
8196 } else {
8197 uint64_t log_entries = write_sz >> SPA_MINBLOCKSHIFT;
8198
8199 uint64_t log_blocks = (log_entries +
8200 dev->l2ad_log_entries - 1) /
8201 dev->l2ad_log_entries;
8202
8203 return (vdev_psize_to_asize(dev->l2ad_vdev,
8204 sizeof (l2arc_log_blk_phys_t)) * log_blocks);
8205 }
8206 }
8207
8208 /*
8209 * Evict buffers from the device write hand to the distance specified in
8210 * bytes. This distance may span populated buffers, it may span nothing.
8211 * This is clearing a region on the L2ARC device ready for writing.
8212 * If the 'all' boolean is set, every buffer is evicted.
8213 */
8214 static void
8215 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
8216 {
8217 list_t *buflist;
8218 arc_buf_hdr_t *hdr, *hdr_prev;
8219 kmutex_t *hash_lock;
8220 uint64_t taddr;
8221 l2arc_lb_ptr_buf_t *lb_ptr_buf, *lb_ptr_buf_prev;
8222 boolean_t rerun;
8223
8224 buflist = &dev->l2ad_buflist;
8225
8226 /*
8227 * We need to add in the worst case scenario of log block overhead.
8228 */
8229 distance += l2arc_log_blk_overhead(distance, dev);
8230
8231 top:
8232 rerun = B_FALSE;
8233 if (dev->l2ad_hand >= (dev->l2ad_end - distance)) {
8234 /*
8235 * When there is no space to accommodate upcoming writes,
8236 * evict to the end. Then bump the write and evict hands
8237 * to the start and iterate. This iteration does not
8238 * happen indefinitely as we make sure in
8239 * l2arc_write_size() that when the write hand is reset,
8240 * the write size does not exceed the end of the device.
8241 */
8242 rerun = B_TRUE;
8243 taddr = dev->l2ad_end;
8244 } else {
8245 taddr = dev->l2ad_hand + distance;
8246 }
8247 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
8248 uint64_t, taddr, boolean_t, all);
8249
8250 /*
8251 * This check has to be placed after deciding whether to iterate
8252 * (rerun).
8253 */
8254 if (!all && dev->l2ad_first) {
8255 /*
8256 * This is the first sweep through the device. There is
8257 * nothing to evict.
8258 */
8259 goto out;
8260 }
8261
8262 /*
8263 * When rebuilding L2ARC we retrieve the evict hand from the header of
8264 * the device. Of note, l2arc_evict() does not actually delete buffers
8265 * from the cache device, but keeping track of the evict hand will be
8266 * useful when TRIM is implemented.
8267 */
8268 dev->l2ad_evict = MAX(dev->l2ad_evict, taddr);
8269
8270 retry:
8271 mutex_enter(&dev->l2ad_mtx);
8272 /*
8273 * We have to account for evicted log blocks. Run vdev_space_update()
8274 * on log blocks whose offset (in bytes) is before the evicted offset
8275 * (in bytes) by searching in the list of pointers to log blocks
8276 * present in the L2ARC device.
8277 */
8278 for (lb_ptr_buf = list_tail(&dev->l2ad_lbptr_list); lb_ptr_buf;
8279 lb_ptr_buf = lb_ptr_buf_prev) {
8280
8281 lb_ptr_buf_prev = list_prev(&dev->l2ad_lbptr_list, lb_ptr_buf);
8282
8283 /* L2BLK_GET_PSIZE returns aligned size for log blocks */
8284 uint64_t asize = L2BLK_GET_PSIZE(
8285 (lb_ptr_buf->lb_ptr)->lbp_prop);
8286
8287 /*
8288 * We don't worry about log blocks left behind (ie
8289 * lbp_payload_start < l2ad_hand) because l2arc_write_buffers()
8290 * will never write more than l2arc_evict() evicts.
8291 */
8292 if (!all && l2arc_log_blkptr_valid(dev, lb_ptr_buf->lb_ptr)) {
8293 break;
8294 } else {
8295 vdev_space_update(dev->l2ad_vdev, -asize, 0, 0);
8296 ARCSTAT_INCR(arcstat_l2_log_blk_asize, -asize);
8297 ARCSTAT_BUMPDOWN(arcstat_l2_log_blk_count);
8298 zfs_refcount_remove_many(&dev->l2ad_lb_asize, asize,
8299 lb_ptr_buf);
8300 zfs_refcount_remove(&dev->l2ad_lb_count, lb_ptr_buf);
8301 list_remove(&dev->l2ad_lbptr_list, lb_ptr_buf);
8302 kmem_free(lb_ptr_buf->lb_ptr,
8303 sizeof (l2arc_log_blkptr_t));
8304 kmem_free(lb_ptr_buf, sizeof (l2arc_lb_ptr_buf_t));
8305 }
8306 }
8307
8308 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
8309 hdr_prev = list_prev(buflist, hdr);
8310
8311 ASSERT(!HDR_EMPTY(hdr));
8312 hash_lock = HDR_LOCK(hdr);
8313
8314 /*
8315 * We cannot use mutex_enter or else we can deadlock
8316 * with l2arc_write_buffers (due to swapping the order
8317 * the hash lock and l2ad_mtx are taken).
8318 */
8319 if (!mutex_tryenter(hash_lock)) {
8320 /*
8321 * Missed the hash lock. Retry.
8322 */
8323 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
8324 mutex_exit(&dev->l2ad_mtx);
8325 mutex_enter(hash_lock);
8326 mutex_exit(hash_lock);
8327 goto retry;
8328 }
8329
8330 /*
8331 * A header can't be on this list if it doesn't have L2 header.
8332 */
8333 ASSERT(HDR_HAS_L2HDR(hdr));
8334
8335 /* Ensure this header has finished being written. */
8336 ASSERT(!HDR_L2_WRITING(hdr));
8337 ASSERT(!HDR_L2_WRITE_HEAD(hdr));
8338
8339 if (!all && (hdr->b_l2hdr.b_daddr >= dev->l2ad_evict ||
8340 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
8341 /*
8342 * We've evicted to the target address,
8343 * or the end of the device.
8344 */
8345 mutex_exit(hash_lock);
8346 break;
8347 }
8348
8349 if (!HDR_HAS_L1HDR(hdr)) {
8350 ASSERT(!HDR_L2_READING(hdr));
8351 /*
8352 * This doesn't exist in the ARC. Destroy.
8353 * arc_hdr_destroy() will call list_remove()
8354 * and decrement arcstat_l2_lsize.
8355 */
8356 arc_change_state(arc_anon, hdr, hash_lock);
8357 arc_hdr_destroy(hdr);
8358 } else {
8359 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
8360 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
8361 /*
8362 * Invalidate issued or about to be issued
8363 * reads, since we may be about to write
8364 * over this location.
8365 */
8366 if (HDR_L2_READING(hdr)) {
8367 ARCSTAT_BUMP(arcstat_l2_evict_reading);
8368 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
8369 }
8370
8371 arc_hdr_l2hdr_destroy(hdr);
8372 }
8373 mutex_exit(hash_lock);
8374 }
8375 mutex_exit(&dev->l2ad_mtx);
8376
8377 out:
8378 /*
8379 * We need to check if we evict all buffers, otherwise we may iterate
8380 * unnecessarily.
8381 */
8382 if (!all && rerun) {
8383 /*
8384 * Bump device hand to the device start if it is approaching the
8385 * end. l2arc_evict() has already evicted ahead for this case.
8386 */
8387 dev->l2ad_hand = dev->l2ad_start;
8388 dev->l2ad_evict = dev->l2ad_start;
8389 dev->l2ad_first = B_FALSE;
8390 goto top;
8391 }
8392
8393 ASSERT3U(dev->l2ad_hand + distance, <, dev->l2ad_end);
8394 if (!dev->l2ad_first)
8395 ASSERT3U(dev->l2ad_hand, <, dev->l2ad_evict);
8396 }
8397
8398 /*
8399 * Handle any abd transforms that might be required for writing to the L2ARC.
8400 * If successful, this function will always return an abd with the data
8401 * transformed as it is on disk in a new abd of asize bytes.
8402 */
8403 static int
8404 l2arc_apply_transforms(spa_t *spa, arc_buf_hdr_t *hdr, uint64_t asize,
8405 abd_t **abd_out)
8406 {
8407 int ret;
8408 void *tmp = NULL;
8409 abd_t *cabd = NULL, *eabd = NULL, *to_write = hdr->b_l1hdr.b_pabd;
8410 enum zio_compress compress = HDR_GET_COMPRESS(hdr);
8411 uint64_t psize = HDR_GET_PSIZE(hdr);
8412 uint64_t size = arc_hdr_size(hdr);
8413 boolean_t ismd = HDR_ISTYPE_METADATA(hdr);
8414 boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
8415 dsl_crypto_key_t *dck = NULL;
8416 uint8_t mac[ZIO_DATA_MAC_LEN] = { 0 };
8417 boolean_t no_crypt = B_FALSE;
8418
8419 ASSERT((HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
8420 !HDR_COMPRESSION_ENABLED(hdr)) ||
8421 HDR_ENCRYPTED(hdr) || HDR_SHARED_DATA(hdr) || psize != asize);
8422 ASSERT3U(psize, <=, asize);
8423
8424 /*
8425 * If this data simply needs its own buffer, we simply allocate it
8426 * and copy the data. This may be done to eliminate a dependency on a
8427 * shared buffer or to reallocate the buffer to match asize.
8428 */
8429 if (HDR_HAS_RABD(hdr) && asize != psize) {
8430 ASSERT3U(asize, >=, psize);
8431 to_write = abd_alloc_for_io(asize, ismd);
8432 abd_copy(to_write, hdr->b_crypt_hdr.b_rabd, psize);
8433 if (psize != asize)
8434 abd_zero_off(to_write, psize, asize - psize);
8435 goto out;
8436 }
8437
8438 if ((compress == ZIO_COMPRESS_OFF || HDR_COMPRESSION_ENABLED(hdr)) &&
8439 !HDR_ENCRYPTED(hdr)) {
8440 ASSERT3U(size, ==, psize);
8441 to_write = abd_alloc_for_io(asize, ismd);
8442 abd_copy(to_write, hdr->b_l1hdr.b_pabd, size);
8443 if (size != asize)
8444 abd_zero_off(to_write, size, asize - size);
8445 goto out;
8446 }
8447
8448 if (compress != ZIO_COMPRESS_OFF && !HDR_COMPRESSION_ENABLED(hdr)) {
8449 cabd = abd_alloc_for_io(asize, ismd);
8450 tmp = abd_borrow_buf(cabd, asize);
8451
8452 psize = zio_compress_data(compress, to_write, tmp, size);
8453 ASSERT3U(psize, <=, HDR_GET_PSIZE(hdr));
8454 if (psize < asize)
8455 bzero((char *)tmp + psize, asize - psize);
8456 psize = HDR_GET_PSIZE(hdr);
8457 abd_return_buf_copy(cabd, tmp, asize);
8458 to_write = cabd;
8459 }
8460
8461 if (HDR_ENCRYPTED(hdr)) {
8462 eabd = abd_alloc_for_io(asize, ismd);
8463
8464 /*
8465 * If the dataset was disowned before the buffer
8466 * made it to this point, the key to re-encrypt
8467 * it won't be available. In this case we simply
8468 * won't write the buffer to the L2ARC.
8469 */
8470 ret = spa_keystore_lookup_key(spa, hdr->b_crypt_hdr.b_dsobj,
8471 FTAG, &dck);
8472 if (ret != 0)
8473 goto error;
8474
8475 ret = zio_do_crypt_abd(B_TRUE, &dck->dck_key,
8476 hdr->b_crypt_hdr.b_ot, bswap, hdr->b_crypt_hdr.b_salt,
8477 hdr->b_crypt_hdr.b_iv, mac, psize, to_write, eabd,
8478 &no_crypt);
8479 if (ret != 0)
8480 goto error;
8481
8482 if (no_crypt)
8483 abd_copy(eabd, to_write, psize);
8484
8485 if (psize != asize)
8486 abd_zero_off(eabd, psize, asize - psize);
8487
8488 /* assert that the MAC we got here matches the one we saved */
8489 ASSERT0(bcmp(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN));
8490 spa_keystore_dsl_key_rele(spa, dck, FTAG);
8491
8492 if (to_write == cabd)
8493 abd_free(cabd);
8494
8495 to_write = eabd;
8496 }
8497
8498 out:
8499 ASSERT3P(to_write, !=, hdr->b_l1hdr.b_pabd);
8500 *abd_out = to_write;
8501 return (0);
8502
8503 error:
8504 if (dck != NULL)
8505 spa_keystore_dsl_key_rele(spa, dck, FTAG);
8506 if (cabd != NULL)
8507 abd_free(cabd);
8508 if (eabd != NULL)
8509 abd_free(eabd);
8510
8511 *abd_out = NULL;
8512 return (ret);
8513 }
8514
8515 static void
8516 l2arc_blk_fetch_done(zio_t *zio)
8517 {
8518 l2arc_read_callback_t *cb;
8519
8520 cb = zio->io_private;
8521 if (cb->l2rcb_abd != NULL)
8522 abd_put(cb->l2rcb_abd);
8523 kmem_free(cb, sizeof (l2arc_read_callback_t));
8524 }
8525
8526 /*
8527 * Find and write ARC buffers to the L2ARC device.
8528 *
8529 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
8530 * for reading until they have completed writing.
8531 * The headroom_boost is an in-out parameter used to maintain headroom boost
8532 * state between calls to this function.
8533 *
8534 * Returns the number of bytes actually written (which may be smaller than
8535 * the delta by which the device hand has changed due to alignment and the
8536 * writing of log blocks).
8537 */
8538 static uint64_t
8539 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
8540 {
8541 arc_buf_hdr_t *hdr, *hdr_prev, *head;
8542 uint64_t write_asize, write_psize, write_lsize, headroom;
8543 boolean_t full;
8544 l2arc_write_callback_t *cb = NULL;
8545 zio_t *pio, *wzio;
8546 uint64_t guid = spa_load_guid(spa);
8547 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
8548
8549 ASSERT3P(dev->l2ad_vdev, !=, NULL);
8550
8551 pio = NULL;
8552 write_lsize = write_asize = write_psize = 0;
8553 full = B_FALSE;
8554 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
8555 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
8556
8557 /*
8558 * Copy buffers for L2ARC writing.
8559 */
8560 for (int try = 0; try < L2ARC_FEED_TYPES; try++) {
8561 /*
8562 * If try == 1 or 3, we cache MRU metadata and data
8563 * respectively.
8564 */
8565 if (l2arc_mfuonly) {
8566 if (try == 1 || try == 3)
8567 continue;
8568 }
8569
8570 multilist_sublist_t *mls = l2arc_sublist_lock(try);
8571 uint64_t passed_sz = 0;
8572
8573 VERIFY3P(mls, !=, NULL);
8574
8575 /*
8576 * L2ARC fast warmup.
8577 *
8578 * Until the ARC is warm and starts to evict, read from the
8579 * head of the ARC lists rather than the tail.
8580 */
8581 if (arc_warm == B_FALSE)
8582 hdr = multilist_sublist_head(mls);
8583 else
8584 hdr = multilist_sublist_tail(mls);
8585
8586 headroom = target_sz * l2arc_headroom;
8587 if (zfs_compressed_arc_enabled)
8588 headroom = (headroom * l2arc_headroom_boost) / 100;
8589
8590 for (; hdr; hdr = hdr_prev) {
8591 kmutex_t *hash_lock;
8592 abd_t *to_write = NULL;
8593
8594 if (arc_warm == B_FALSE)
8595 hdr_prev = multilist_sublist_next(mls, hdr);
8596 else
8597 hdr_prev = multilist_sublist_prev(mls, hdr);
8598
8599 hash_lock = HDR_LOCK(hdr);
8600 if (!mutex_tryenter(hash_lock)) {
8601 /*
8602 * Skip this buffer rather than waiting.
8603 */
8604 continue;
8605 }
8606
8607 passed_sz += HDR_GET_LSIZE(hdr);
8608 if (l2arc_headroom != 0 && passed_sz > headroom) {
8609 /*
8610 * Searched too far.
8611 */
8612 mutex_exit(hash_lock);
8613 break;
8614 }
8615
8616 if (!l2arc_write_eligible(guid, hdr)) {
8617 mutex_exit(hash_lock);
8618 continue;
8619 }
8620
8621 /*
8622 * We rely on the L1 portion of the header below, so
8623 * it's invalid for this header to have been evicted out
8624 * of the ghost cache, prior to being written out. The
8625 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
8626 */
8627 ASSERT(HDR_HAS_L1HDR(hdr));
8628
8629 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
8630 ASSERT3U(arc_hdr_size(hdr), >, 0);
8631 ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
8632 HDR_HAS_RABD(hdr));
8633 uint64_t psize = HDR_GET_PSIZE(hdr);
8634 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
8635 psize);
8636
8637 if ((write_asize + asize) > target_sz) {
8638 full = B_TRUE;
8639 mutex_exit(hash_lock);
8640 break;
8641 }
8642
8643 /*
8644 * We rely on the L1 portion of the header below, so
8645 * it's invalid for this header to have been evicted out
8646 * of the ghost cache, prior to being written out. The
8647 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
8648 */
8649 arc_hdr_set_flags(hdr, ARC_FLAG_L2_WRITING);
8650 ASSERT(HDR_HAS_L1HDR(hdr));
8651
8652 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
8653 ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
8654 HDR_HAS_RABD(hdr));
8655 ASSERT3U(arc_hdr_size(hdr), >, 0);
8656
8657 /*
8658 * If this header has b_rabd, we can use this since it
8659 * must always match the data exactly as it exists on
8660 * disk. Otherwise, the L2ARC can normally use the
8661 * hdr's data, but if we're sharing data between the
8662 * hdr and one of its bufs, L2ARC needs its own copy of
8663 * the data so that the ZIO below can't race with the
8664 * buf consumer. To ensure that this copy will be
8665 * available for the lifetime of the ZIO and be cleaned
8666 * up afterwards, we add it to the l2arc_free_on_write
8667 * queue. If we need to apply any transforms to the
8668 * data (compression, encryption) we will also need the
8669 * extra buffer.
8670 */
8671 if (HDR_HAS_RABD(hdr) && psize == asize) {
8672 to_write = hdr->b_crypt_hdr.b_rabd;
8673 } else if ((HDR_COMPRESSION_ENABLED(hdr) ||
8674 HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) &&
8675 !HDR_ENCRYPTED(hdr) && !HDR_SHARED_DATA(hdr) &&
8676 psize == asize) {
8677 to_write = hdr->b_l1hdr.b_pabd;
8678 } else {
8679 int ret;
8680 arc_buf_contents_t type = arc_buf_type(hdr);
8681
8682 ret = l2arc_apply_transforms(spa, hdr, asize,
8683 &to_write);
8684 if (ret != 0) {
8685 arc_hdr_clear_flags(hdr,
8686 ARC_FLAG_L2_WRITING);
8687 mutex_exit(hash_lock);
8688 continue;
8689 }
8690
8691 l2arc_free_abd_on_write(to_write, asize, type);
8692 }
8693
8694 if (pio == NULL) {
8695 /*
8696 * Insert a dummy header on the buflist so
8697 * l2arc_write_done() can find where the
8698 * write buffers begin without searching.
8699 */
8700 mutex_enter(&dev->l2ad_mtx);
8701 list_insert_head(&dev->l2ad_buflist, head);
8702 mutex_exit(&dev->l2ad_mtx);
8703
8704 cb = kmem_alloc(
8705 sizeof (l2arc_write_callback_t), KM_SLEEP);
8706 cb->l2wcb_dev = dev;
8707 cb->l2wcb_head = head;
8708 /*
8709 * Create a list to save allocated abd buffers
8710 * for l2arc_log_blk_commit().
8711 */
8712 list_create(&cb->l2wcb_abd_list,
8713 sizeof (l2arc_lb_abd_buf_t),
8714 offsetof(l2arc_lb_abd_buf_t, node));
8715 pio = zio_root(spa, l2arc_write_done, cb,
8716 ZIO_FLAG_CANFAIL);
8717 }
8718
8719 hdr->b_l2hdr.b_dev = dev;
8720 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
8721 hdr->b_l2hdr.b_arcs_state =
8722 hdr->b_l1hdr.b_state->arcs_state;
8723 arc_hdr_set_flags(hdr,
8724 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);
8725
8726 mutex_enter(&dev->l2ad_mtx);
8727 list_insert_head(&dev->l2ad_buflist, hdr);
8728 mutex_exit(&dev->l2ad_mtx);
8729
8730 (void) zfs_refcount_add_many(&dev->l2ad_alloc,
8731 arc_hdr_size(hdr), hdr);
8732
8733 wzio = zio_write_phys(pio, dev->l2ad_vdev,
8734 hdr->b_l2hdr.b_daddr, asize, to_write,
8735 ZIO_CHECKSUM_OFF, NULL, hdr,
8736 ZIO_PRIORITY_ASYNC_WRITE,
8737 ZIO_FLAG_CANFAIL, B_FALSE);
8738
8739 write_lsize += HDR_GET_LSIZE(hdr);
8740 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
8741 zio_t *, wzio);
8742
8743 write_psize += psize;
8744 write_asize += asize;
8745 dev->l2ad_hand += asize;
8746 l2arc_hdr_arcstats_increment(hdr);
8747 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
8748
8749 mutex_exit(hash_lock);
8750
8751 /*
8752 * Append buf info to current log and commit if full.
8753 * arcstat_l2_{size,asize} kstats are updated
8754 * internally.
8755 */
8756 if (l2arc_log_blk_insert(dev, hdr))
8757 l2arc_log_blk_commit(dev, pio, cb);
8758
8759 (void) zio_nowait(wzio);
8760 }
8761
8762 multilist_sublist_unlock(mls);
8763
8764 if (full == B_TRUE)
8765 break;
8766 }
8767
8768 /* No buffers selected for writing? */
8769 if (pio == NULL) {
8770 ASSERT0(write_lsize);
8771 ASSERT(!HDR_HAS_L1HDR(head));
8772 kmem_cache_free(hdr_l2only_cache, head);
8773
8774 /*
8775 * Although we did not write any buffers l2ad_evict may
8776 * have advanced.
8777 */
8778 if (dev->l2ad_evict != l2dhdr->dh_evict)
8779 l2arc_dev_hdr_update(dev);
8780
8781 return (0);
8782 }
8783
8784 if (!dev->l2ad_first)
8785 ASSERT3U(dev->l2ad_hand, <=, dev->l2ad_evict);
8786
8787 ASSERT3U(write_asize, <=, target_sz);
8788 ARCSTAT_BUMP(arcstat_l2_writes_sent);
8789 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize);
8790
8791 dev->l2ad_writing = B_TRUE;
8792 (void) zio_wait(pio);
8793 dev->l2ad_writing = B_FALSE;
8794
8795 /*
8796 * Update the device header after the zio completes as
8797 * l2arc_write_done() may have updated the memory holding the log block
8798 * pointers in the device header.
8799 */
8800 l2arc_dev_hdr_update(dev);
8801
8802 return (write_asize);
8803 }
8804
8805 static boolean_t
8806 l2arc_hdr_limit_reached(void)
8807 {
8808 int64_t s = aggsum_upper_bound(&astat_l2_hdr_size);
8809
8810 return (arc_reclaim_needed() || (s > arc_meta_limit * 3 / 4) ||
8811 (s > (arc_warm ? arc_c : arc_c_max) * l2arc_meta_percent / 100));
8812 }
8813
8814 /*
8815 * This thread feeds the L2ARC at regular intervals. This is the beating
8816 * heart of the L2ARC.
8817 */
8818 /* ARGSUSED */
8819 static void
8820 l2arc_feed_thread(void *unused)
8821 {
8822 callb_cpr_t cpr;
8823 l2arc_dev_t *dev;
8824 spa_t *spa;
8825 uint64_t size, wrote;
8826 clock_t begin, next = ddi_get_lbolt();
8827
8828 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
8829
8830 mutex_enter(&l2arc_feed_thr_lock);
8831
8832 while (l2arc_thread_exit == 0) {
8833 CALLB_CPR_SAFE_BEGIN(&cpr);
8834 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
8835 next);
8836 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
8837 next = ddi_get_lbolt() + hz;
8838
8839 /*
8840 * Quick check for L2ARC devices.
8841 */
8842 mutex_enter(&l2arc_dev_mtx);
8843 if (l2arc_ndev == 0) {
8844 mutex_exit(&l2arc_dev_mtx);
8845 continue;
8846 }
8847 mutex_exit(&l2arc_dev_mtx);
8848 begin = ddi_get_lbolt();
8849
8850 /*
8851 * This selects the next l2arc device to write to, and in
8852 * doing so the next spa to feed from: dev->l2ad_spa. This
8853 * will return NULL if there are now no l2arc devices or if
8854 * they are all faulted.
8855 *
8856 * If a device is returned, its spa's config lock is also
8857 * held to prevent device removal. l2arc_dev_get_next()
8858 * will grab and release l2arc_dev_mtx.
8859 */
8860 if ((dev = l2arc_dev_get_next()) == NULL)
8861 continue;
8862
8863 spa = dev->l2ad_spa;
8864 ASSERT3P(spa, !=, NULL);
8865
8866 /*
8867 * If the pool is read-only then force the feed thread to
8868 * sleep a little longer.
8869 */
8870 if (!spa_writeable(spa)) {
8871 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
8872 spa_config_exit(spa, SCL_L2ARC, dev);
8873 continue;
8874 }
8875
8876 /*
8877 * Avoid contributing to memory pressure.
8878 */
8879 if (l2arc_hdr_limit_reached()) {
8880 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
8881 spa_config_exit(spa, SCL_L2ARC, dev);
8882 continue;
8883 }
8884
8885 ARCSTAT_BUMP(arcstat_l2_feeds);
8886
8887 size = l2arc_write_size(dev);
8888
8889 /*
8890 * Evict L2ARC buffers that will be overwritten.
8891 */
8892 l2arc_evict(dev, size, B_FALSE);
8893
8894 /*
8895 * Write ARC buffers.
8896 */
8897 wrote = l2arc_write_buffers(spa, dev, size);
8898
8899 /*
8900 * Calculate interval between writes.
8901 */
8902 next = l2arc_write_interval(begin, size, wrote);
8903 spa_config_exit(spa, SCL_L2ARC, dev);
8904 }
8905
8906 l2arc_thread_exit = 0;
8907 cv_broadcast(&l2arc_feed_thr_cv);
8908 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
8909 thread_exit();
8910 }
8911
8912 boolean_t
8913 l2arc_vdev_present(vdev_t *vd)
8914 {
8915 return (l2arc_vdev_get(vd) != NULL);
8916 }
8917
8918 /*
8919 * Returns the l2arc_dev_t associated with a particular vdev_t or NULL if
8920 * the vdev_t isn't an L2ARC device.
8921 */
8922 static l2arc_dev_t *
8923 l2arc_vdev_get(vdev_t *vd)
8924 {
8925 l2arc_dev_t *dev;
8926
8927 mutex_enter(&l2arc_dev_mtx);
8928 for (dev = list_head(l2arc_dev_list); dev != NULL;
8929 dev = list_next(l2arc_dev_list, dev)) {
8930 if (dev->l2ad_vdev == vd)
8931 break;
8932 }
8933 mutex_exit(&l2arc_dev_mtx);
8934
8935 return (dev);
8936 }
8937
8938 /*
8939 * Add a vdev for use by the L2ARC. By this point the spa has already
8940 * validated the vdev and opened it.
8941 */
8942 void
8943 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
8944 {
8945 l2arc_dev_t *adddev;
8946 uint64_t l2dhdr_asize;
8947
8948 ASSERT(!l2arc_vdev_present(vd));
8949
8950 /*
8951 * Create a new l2arc device entry.
8952 */
8953 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
8954 adddev->l2ad_spa = spa;
8955 adddev->l2ad_vdev = vd;
8956 /* leave extra size for an l2arc device header */
8957 l2dhdr_asize = adddev->l2ad_dev_hdr_asize =
8958 MAX(sizeof (*adddev->l2ad_dev_hdr), 1 << vd->vdev_ashift);
8959 adddev->l2ad_start = VDEV_LABEL_START_SIZE + l2dhdr_asize;
8960 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
8961 ASSERT3U(adddev->l2ad_start, <, adddev->l2ad_end);
8962 adddev->l2ad_hand = adddev->l2ad_start;
8963 adddev->l2ad_evict = adddev->l2ad_start;
8964 adddev->l2ad_first = B_TRUE;
8965 adddev->l2ad_writing = B_FALSE;
8966 adddev->l2ad_dev_hdr = kmem_zalloc(l2dhdr_asize, KM_SLEEP);
8967
8968 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
8969 /*
8970 * This is a list of all ARC buffers that are still valid on the
8971 * device.
8972 */
8973 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
8974 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
8975
8976 /*
8977 * This is a list of pointers to log blocks that are still present
8978 * on the device.
8979 */
8980 list_create(&adddev->l2ad_lbptr_list, sizeof (l2arc_lb_ptr_buf_t),
8981 offsetof(l2arc_lb_ptr_buf_t, node));
8982
8983 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
8984 zfs_refcount_create(&adddev->l2ad_alloc);
8985 zfs_refcount_create(&adddev->l2ad_lb_asize);
8986 zfs_refcount_create(&adddev->l2ad_lb_count);
8987
8988 /*
8989 * Add device to global list
8990 */
8991 mutex_enter(&l2arc_dev_mtx);
8992 list_insert_head(l2arc_dev_list, adddev);
8993 atomic_inc_64(&l2arc_ndev);
8994 mutex_exit(&l2arc_dev_mtx);
8995
8996 /*
8997 * Decide if vdev is eligible for L2ARC rebuild
8998 */
8999 l2arc_rebuild_vdev(adddev->l2ad_vdev, B_FALSE);
9000 }
9001
9002 void
9003 l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen)
9004 {
9005 l2arc_dev_t *dev = NULL;
9006 l2arc_dev_hdr_phys_t *l2dhdr;
9007 uint64_t l2dhdr_asize;
9008 spa_t *spa;
9009
9010 dev = l2arc_vdev_get(vd);
9011 ASSERT3P(dev, !=, NULL);
9012 spa = dev->l2ad_spa;
9013 l2dhdr = dev->l2ad_dev_hdr;
9014 l2dhdr_asize = dev->l2ad_dev_hdr_asize;
9015
9016 /*
9017 * The L2ARC has to hold at least the payload of one log block for
9018 * them to be restored (persistent L2ARC). The payload of a log block
9019 * depends on the amount of its log entries. We always write log blocks
9020 * with 1022 entries. How many of them are committed or restored depends
9021 * on the size of the L2ARC device. Thus the maximum payload of
9022 * one log block is 1022 * SPA_MAXBLOCKSIZE = 16GB. If the L2ARC device
9023 * is less than that, we reduce the amount of committed and restored
9024 * log entries per block so as to enable persistence.
9025 */
9026 if (dev->l2ad_end < l2arc_rebuild_blocks_min_l2size) {
9027 dev->l2ad_log_entries = 0;
9028 } else {
9029 dev->l2ad_log_entries = MIN((dev->l2ad_end -
9030 dev->l2ad_start) >> SPA_MAXBLOCKSHIFT,
9031 L2ARC_LOG_BLK_MAX_ENTRIES);
9032 }
9033
9034 /*
9035 * Read the device header, if an error is returned do not rebuild L2ARC.
9036 */
9037 if (l2arc_dev_hdr_read(dev) == 0 && dev->l2ad_log_entries > 0) {
9038 /*
9039 * If we are onlining a cache device (vdev_reopen) that was
9040 * still present (l2arc_vdev_present()) and rebuild is enabled,
9041 * we should evict all ARC buffers and pointers to log blocks
9042 * and reclaim their space before restoring its contents to
9043 * L2ARC.
9044 */
9045 if (reopen) {
9046 if (!l2arc_rebuild_enabled) {
9047 return;
9048 } else {
9049 l2arc_evict(dev, 0, B_TRUE);
9050 /* start a new log block */
9051 dev->l2ad_log_ent_idx = 0;
9052 dev->l2ad_log_blk_payload_asize = 0;
9053 dev->l2ad_log_blk_payload_start = 0;
9054 }
9055 }
9056 /*
9057 * Just mark the device as pending for a rebuild. We won't
9058 * be starting a rebuild in line here as it would block pool
9059 * import. Instead spa_load_impl will hand that off to an
9060 * async task which will call l2arc_spa_rebuild_start.
9061 */
9062 dev->l2ad_rebuild = B_TRUE;
9063 } else if (spa_writeable(spa)) {
9064 /*
9065 * In this case create a new header. We zero out the memory
9066 * holding the header to reset dh_start_lbps.
9067 */
9068 bzero(l2dhdr, l2dhdr_asize);
9069 l2arc_dev_hdr_update(dev);
9070 }
9071 }
9072
9073 /*
9074 * Remove a vdev from the L2ARC.
9075 */
9076 void
9077 l2arc_remove_vdev(vdev_t *vd)
9078 {
9079 l2arc_dev_t *remdev = NULL;
9080
9081 /*
9082 * Find the device by vdev
9083 */
9084 remdev = l2arc_vdev_get(vd);
9085 ASSERT3P(remdev, !=, NULL);
9086
9087 /*
9088 * Cancel any ongoing or scheduled rebuild.
9089 */
9090 mutex_enter(&l2arc_rebuild_thr_lock);
9091 if (remdev->l2ad_rebuild_began == B_TRUE) {
9092 remdev->l2ad_rebuild_cancel = B_TRUE;
9093 while (remdev->l2ad_rebuild == B_TRUE)
9094 cv_wait(&l2arc_rebuild_thr_cv, &l2arc_rebuild_thr_lock);
9095 }
9096 mutex_exit(&l2arc_rebuild_thr_lock);
9097
9098 /*
9099 * Remove device from global list
9100 */
9101 mutex_enter(&l2arc_dev_mtx);
9102 list_remove(l2arc_dev_list, remdev);
9103 l2arc_dev_last = NULL; /* may have been invalidated */
9104 atomic_dec_64(&l2arc_ndev);
9105 mutex_exit(&l2arc_dev_mtx);
9106
9107 /*
9108 * Clear all buflists and ARC references. L2ARC device flush.
9109 */
9110 l2arc_evict(remdev, 0, B_TRUE);
9111 list_destroy(&remdev->l2ad_buflist);
9112 ASSERT(list_is_empty(&remdev->l2ad_lbptr_list));
9113 list_destroy(&remdev->l2ad_lbptr_list);
9114 mutex_destroy(&remdev->l2ad_mtx);
9115 zfs_refcount_destroy(&remdev->l2ad_alloc);
9116 zfs_refcount_destroy(&remdev->l2ad_lb_asize);
9117 zfs_refcount_destroy(&remdev->l2ad_lb_count);
9118 kmem_free(remdev->l2ad_dev_hdr, remdev->l2ad_dev_hdr_asize);
9119 kmem_free(remdev, sizeof (l2arc_dev_t));
9120 }
9121
9122 void
9123 l2arc_init(void)
9124 {
9125 l2arc_thread_exit = 0;
9126 l2arc_ndev = 0;
9127 l2arc_writes_sent = 0;
9128 l2arc_writes_done = 0;
9129
9130 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
9131 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
9132 mutex_init(&l2arc_rebuild_thr_lock, NULL, MUTEX_DEFAULT, NULL);
9133 cv_init(&l2arc_rebuild_thr_cv, NULL, CV_DEFAULT, NULL);
9134 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
9135 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
9136
9137 l2arc_dev_list = &L2ARC_dev_list;
9138 l2arc_free_on_write = &L2ARC_free_on_write;
9139 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
9140 offsetof(l2arc_dev_t, l2ad_node));
9141 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
9142 offsetof(l2arc_data_free_t, l2df_list_node));
9143 }
9144
9145 void
9146 l2arc_fini(void)
9147 {
9148 /*
9149 * This is called from dmu_fini(), which is called from spa_fini();
9150 * Because of this, we can assume that all l2arc devices have
9151 * already been removed when the pools themselves were removed.
9152 */
9153
9154 l2arc_do_free_on_write();
9155
9156 mutex_destroy(&l2arc_feed_thr_lock);
9157 cv_destroy(&l2arc_feed_thr_cv);
9158 mutex_destroy(&l2arc_rebuild_thr_lock);
9159 cv_destroy(&l2arc_rebuild_thr_cv);
9160 mutex_destroy(&l2arc_dev_mtx);
9161 mutex_destroy(&l2arc_free_on_write_mtx);
9162
9163 list_destroy(l2arc_dev_list);
9164 list_destroy(l2arc_free_on_write);
9165 }
9166
9167 void
9168 l2arc_start(void)
9169 {
9170 if (!(spa_mode_global & FWRITE))
9171 return;
9172
9173 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
9174 TS_RUN, minclsyspri);
9175 }
9176
9177 void
9178 l2arc_stop(void)
9179 {
9180 if (!(spa_mode_global & FWRITE))
9181 return;
9182
9183 mutex_enter(&l2arc_feed_thr_lock);
9184 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
9185 l2arc_thread_exit = 1;
9186 while (l2arc_thread_exit != 0)
9187 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
9188 mutex_exit(&l2arc_feed_thr_lock);
9189 }
9190
9191 /*
9192 * Punches out rebuild threads for the L2ARC devices in a spa. This should
9193 * be called after pool import from the spa async thread, since starting
9194 * these threads directly from spa_import() will make them part of the
9195 * "zpool import" context and delay process exit (and thus pool import).
9196 */
9197 void
9198 l2arc_spa_rebuild_start(spa_t *spa)
9199 {
9200 ASSERT(MUTEX_HELD(&spa_namespace_lock));
9201
9202 /*
9203 * Locate the spa's l2arc devices and kick off rebuild threads.
9204 */
9205 for (int i = 0; i < spa->spa_l2cache.sav_count; i++) {
9206 l2arc_dev_t *dev =
9207 l2arc_vdev_get(spa->spa_l2cache.sav_vdevs[i]);
9208 if (dev == NULL) {
9209 /* Don't attempt a rebuild if the vdev is UNAVAIL */
9210 continue;
9211 }
9212 mutex_enter(&l2arc_rebuild_thr_lock);
9213 if (dev->l2ad_rebuild && !dev->l2ad_rebuild_cancel) {
9214 dev->l2ad_rebuild_began = B_TRUE;
9215 (void) thread_create(NULL, 0,
9216 (void (*)(void *))l2arc_dev_rebuild_start,
9217 dev, 0, &p0, TS_RUN, minclsyspri);
9218 }
9219 mutex_exit(&l2arc_rebuild_thr_lock);
9220 }
9221 }
9222
9223 /*
9224 * Main entry point for L2ARC rebuilding.
9225 */
9226 static void
9227 l2arc_dev_rebuild_start(l2arc_dev_t *dev)
9228 {
9229 VERIFY(!dev->l2ad_rebuild_cancel);
9230 VERIFY(dev->l2ad_rebuild);
9231 (void) l2arc_rebuild(dev);
9232 mutex_enter(&l2arc_rebuild_thr_lock);
9233 dev->l2ad_rebuild_began = B_FALSE;
9234 dev->l2ad_rebuild = B_FALSE;
9235 mutex_exit(&l2arc_rebuild_thr_lock);
9236
9237 thread_exit();
9238 }
9239
9240 /*
9241 * This function implements the actual L2ARC metadata rebuild. It:
9242 * starts reading the log block chain and restores each block's contents
9243 * to memory (reconstructing arc_buf_hdr_t's).
9244 *
9245 * Operation stops under any of the following conditions:
9246 *
9247 * 1) We reach the end of the log block chain.
9248 * 2) We encounter *any* error condition (cksum errors, io errors)
9249 */
9250 static int
9251 l2arc_rebuild(l2arc_dev_t *dev)
9252 {
9253 vdev_t *vd = dev->l2ad_vdev;
9254 spa_t *spa = vd->vdev_spa;
9255 int err = 0;
9256 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
9257 l2arc_log_blk_phys_t *this_lb, *next_lb;
9258 zio_t *this_io = NULL, *next_io = NULL;
9259 l2arc_log_blkptr_t lbps[2];
9260 l2arc_lb_ptr_buf_t *lb_ptr_buf;
9261 boolean_t lock_held;
9262
9263 this_lb = kmem_zalloc(sizeof (*this_lb), KM_SLEEP);
9264 next_lb = kmem_zalloc(sizeof (*next_lb), KM_SLEEP);
9265
9266 /*
9267 * We prevent device removal while issuing reads to the device,
9268 * then during the rebuilding phases we drop this lock again so
9269 * that a spa_unload or device remove can be initiated - this is
9270 * safe, because the spa will signal us to stop before removing
9271 * our device and wait for us to stop.
9272 */
9273 spa_config_enter(spa, SCL_L2ARC, vd, RW_READER);
9274 lock_held = B_TRUE;
9275
9276 /*
9277 * Retrieve the persistent L2ARC device state.
9278 * L2BLK_GET_PSIZE returns aligned size for log blocks.
9279 */
9280 dev->l2ad_evict = MAX(l2dhdr->dh_evict, dev->l2ad_start);
9281 dev->l2ad_hand = MAX(l2dhdr->dh_start_lbps[0].lbp_daddr +
9282 L2BLK_GET_PSIZE((&l2dhdr->dh_start_lbps[0])->lbp_prop),
9283 dev->l2ad_start);
9284 dev->l2ad_first = !!(l2dhdr->dh_flags & L2ARC_DEV_HDR_EVICT_FIRST);
9285
9286 /*
9287 * In case the zfs module parameter l2arc_rebuild_enabled is false
9288 * we do not start the rebuild process.
9289 */
9290 if (!l2arc_rebuild_enabled)
9291 goto out;
9292
9293 /* Prepare the rebuild process */
9294 bcopy(l2dhdr->dh_start_lbps, lbps, sizeof (lbps));
9295
9296 /* Start the rebuild process */
9297 for (;;) {
9298 if (!l2arc_log_blkptr_valid(dev, &lbps[0]))
9299 break;
9300
9301 if ((err = l2arc_log_blk_read(dev, &lbps[0], &lbps[1],
9302 this_lb, next_lb, this_io, &next_io)) != 0)
9303 goto out;
9304
9305 /*
9306 * Our memory pressure valve. If the system is running low
9307 * on memory, rather than swamping memory with new ARC buf
9308 * hdrs, we opt not to rebuild the L2ARC. At this point,
9309 * however, we have already set up our L2ARC dev to chain in
9310 * new metadata log blocks, so the user may choose to offline/
9311 * online the L2ARC dev at a later time (or re-import the pool)
9312 * to reconstruct it (when there's less memory pressure).
9313 */
9314 if (l2arc_hdr_limit_reached()) {
9315 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_lowmem);
9316 cmn_err(CE_NOTE, "System running low on memory, "
9317 "aborting L2ARC rebuild.");
9318 err = SET_ERROR(ENOMEM);
9319 goto out;
9320 }
9321
9322 spa_config_exit(spa, SCL_L2ARC, vd);
9323 lock_held = B_FALSE;
9324
9325 /*
9326 * Now that we know that the next_lb checks out alright, we
9327 * can start reconstruction from this log block.
9328 * L2BLK_GET_PSIZE returns aligned size for log blocks.
9329 */
9330 uint64_t asize = L2BLK_GET_PSIZE((&lbps[0])->lbp_prop);
9331 l2arc_log_blk_restore(dev, this_lb, asize);
9332
9333 /*
9334 * log block restored, include its pointer in the list of
9335 * pointers to log blocks present in the L2ARC device.
9336 */
9337 lb_ptr_buf = kmem_zalloc(sizeof (l2arc_lb_ptr_buf_t), KM_SLEEP);
9338 lb_ptr_buf->lb_ptr = kmem_zalloc(sizeof (l2arc_log_blkptr_t),
9339 KM_SLEEP);
9340 bcopy(&lbps[0], lb_ptr_buf->lb_ptr,
9341 sizeof (l2arc_log_blkptr_t));
9342 mutex_enter(&dev->l2ad_mtx);
9343 list_insert_tail(&dev->l2ad_lbptr_list, lb_ptr_buf);
9344 ARCSTAT_INCR(arcstat_l2_log_blk_asize, asize);
9345 ARCSTAT_BUMP(arcstat_l2_log_blk_count);
9346 zfs_refcount_add_many(&dev->l2ad_lb_asize, asize, lb_ptr_buf);
9347 zfs_refcount_add(&dev->l2ad_lb_count, lb_ptr_buf);
9348 mutex_exit(&dev->l2ad_mtx);
9349 vdev_space_update(vd, asize, 0, 0);
9350
9351 /* BEGIN CSTYLED */
9352 /*
9353 * Protection against loops of log blocks:
9354 *
9355 * l2ad_hand l2ad_evict
9356 * V V
9357 * l2ad_start |=======================================| l2ad_end
9358 * -----|||----|||---|||----|||
9359 * (3) (2) (1) (0)
9360 * ---|||---|||----|||---|||
9361 * (7) (6) (5) (4)
9362 *
9363 * In this situation the pointer of log block (4) passes
9364 * l2arc_log_blkptr_valid() but the log block should not be
9365 * restored as it is overwritten by the payload of log block
9366 * (0). Only log blocks (0)-(3) should be restored. We check
9367 * whether l2ad_evict lies in between the payload starting
9368 * offset of the next log block (lbps[1].lbp_payload_start)
9369 * and the payload starting offset of the present log block
9370 * (lbps[0].lbp_payload_start). If true and this isn't the
9371 * first pass, we are looping from the beginning and we should
9372 * stop.
9373 */
9374 /* END CSTYLED */
9375 if (l2arc_range_check_overlap(lbps[1].lbp_payload_start,
9376 lbps[0].lbp_payload_start, dev->l2ad_evict) &&
9377 !dev->l2ad_first)
9378 goto out;
9379
9380 for (;;) {
9381 mutex_enter(&l2arc_rebuild_thr_lock);
9382 if (dev->l2ad_rebuild_cancel) {
9383 dev->l2ad_rebuild = B_FALSE;
9384 cv_signal(&l2arc_rebuild_thr_cv);
9385 mutex_exit(&l2arc_rebuild_thr_lock);
9386 err = SET_ERROR(ECANCELED);
9387 goto out;
9388 }
9389 mutex_exit(&l2arc_rebuild_thr_lock);
9390 if (spa_config_tryenter(spa, SCL_L2ARC, vd,
9391 RW_READER)) {
9392 lock_held = B_TRUE;
9393 break;
9394 }
9395 /*
9396 * L2ARC config lock held by somebody in writer,
9397 * possibly due to them trying to remove us. They'll
9398 * likely to want us to shut down, so after a little
9399 * delay, we check l2ad_rebuild_cancel and retry
9400 * the lock again.
9401 */
9402 delay(1);
9403 }
9404
9405 /*
9406 * Continue with the next log block.
9407 */
9408 lbps[0] = lbps[1];
9409 lbps[1] = this_lb->lb_prev_lbp;
9410 PTR_SWAP(this_lb, next_lb);
9411 this_io = next_io;
9412 next_io = NULL;
9413 }
9414
9415 if (this_io != NULL)
9416 l2arc_log_blk_fetch_abort(this_io);
9417 out:
9418 if (next_io != NULL)
9419 l2arc_log_blk_fetch_abort(next_io);
9420 kmem_free(this_lb, sizeof (*this_lb));
9421 kmem_free(next_lb, sizeof (*next_lb));
9422
9423 if (!l2arc_rebuild_enabled) {
9424 spa_history_log_internal(spa, "L2ARC rebuild", NULL,
9425 "disabled");
9426 } else if (err == 0 && zfs_refcount_count(&dev->l2ad_lb_count) > 0) {
9427 ARCSTAT_BUMP(arcstat_l2_rebuild_success);
9428 spa_history_log_internal(spa, "L2ARC rebuild", NULL,
9429 "successful, restored %llu blocks",
9430 (u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count));
9431 } else if (err == 0 && zfs_refcount_count(&dev->l2ad_lb_count) == 0) {
9432 /*
9433 * No error but also nothing restored, meaning the lbps array
9434 * in the device header points to invalid/non-present log
9435 * blocks. Reset the header.
9436 */
9437 spa_history_log_internal(spa, "L2ARC rebuild", NULL,
9438 "no valid log blocks");
9439 bzero(l2dhdr, dev->l2ad_dev_hdr_asize);
9440 l2arc_dev_hdr_update(dev);
9441 } else if (err == ECANCELED) {
9442 /*
9443 * In case the rebuild was canceled do not log to spa history
9444 * log as the pool may be in the process of being removed.
9445 */
9446 zfs_dbgmsg("L2ARC rebuild aborted, restored %llu blocks",
9447 zfs_refcount_count(&dev->l2ad_lb_count));
9448 } else if (err != 0) {
9449 spa_history_log_internal(spa, "L2ARC rebuild", NULL,
9450 "aborted, restored %llu blocks",
9451 (u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count));
9452 }
9453
9454 if (lock_held)
9455 spa_config_exit(spa, SCL_L2ARC, vd);
9456
9457 return (err);
9458 }
9459
9460 /*
9461 * Attempts to read the device header on the provided L2ARC device and writes
9462 * it to `hdr'. On success, this function returns 0, otherwise the appropriate
9463 * error code is returned.
9464 */
9465 static int
9466 l2arc_dev_hdr_read(l2arc_dev_t *dev)
9467 {
9468 int err;
9469 uint64_t guid;
9470 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
9471 const uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize;
9472 abd_t *abd;
9473
9474 guid = spa_guid(dev->l2ad_vdev->vdev_spa);
9475
9476 abd = abd_get_from_buf(l2dhdr, l2dhdr_asize);
9477
9478 err = zio_wait(zio_read_phys(NULL, dev->l2ad_vdev,
9479 VDEV_LABEL_START_SIZE, l2dhdr_asize, abd,
9480 ZIO_CHECKSUM_LABEL, NULL, NULL, ZIO_PRIORITY_SYNC_READ,
9481 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
9482 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY |
9483 ZIO_FLAG_SPECULATIVE, B_FALSE));
9484
9485 abd_put(abd);
9486
9487 if (err != 0) {
9488 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_dh_errors);
9489 zfs_dbgmsg("L2ARC IO error (%d) while reading device header, "
9490 "vdev guid: %llu", err, dev->l2ad_vdev->vdev_guid);
9491 return (err);
9492 }
9493
9494 if (l2dhdr->dh_magic == BSWAP_64(L2ARC_DEV_HDR_MAGIC))
9495 byteswap_uint64_array(l2dhdr, sizeof (*l2dhdr));
9496
9497 if (l2dhdr->dh_magic != L2ARC_DEV_HDR_MAGIC ||
9498 l2dhdr->dh_spa_guid != guid ||
9499 l2dhdr->dh_vdev_guid != dev->l2ad_vdev->vdev_guid ||
9500 l2dhdr->dh_version != L2ARC_PERSISTENT_VERSION ||
9501 l2dhdr->dh_log_entries != dev->l2ad_log_entries ||
9502 l2dhdr->dh_end != dev->l2ad_end ||
9503 !l2arc_range_check_overlap(dev->l2ad_start, dev->l2ad_end,
9504 l2dhdr->dh_evict)) {
9505 /*
9506 * Attempt to rebuild a device containing no actual dev hdr
9507 * or containing a header from some other pool or from another
9508 * version of persistent L2ARC.
9509 */
9510 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_unsupported);
9511 return (SET_ERROR(ENOTSUP));
9512 }
9513
9514 return (0);
9515 }
9516
9517 /*
9518 * Reads L2ARC log blocks from storage and validates their contents.
9519 *
9520 * This function implements a simple fetcher to make sure that while
9521 * we're processing one buffer the L2ARC is already fetching the next
9522 * one in the chain.
9523 *
9524 * The arguments this_lp and next_lp point to the current and next log block
9525 * address in the block chain. Similarly, this_lb and next_lb hold the
9526 * l2arc_log_blk_phys_t's of the current and next L2ARC blk.
9527 *
9528 * The `this_io' and `next_io' arguments are used for block fetching.
9529 * When issuing the first blk IO during rebuild, you should pass NULL for
9530 * `this_io'. This function will then issue a sync IO to read the block and
9531 * also issue an async IO to fetch the next block in the block chain. The
9532 * fetched IO is returned in `next_io'. On subsequent calls to this
9533 * function, pass the value returned in `next_io' from the previous call
9534 * as `this_io' and a fresh `next_io' pointer to hold the next fetch IO.
9535 * Prior to the call, you should initialize your `next_io' pointer to be
9536 * NULL. If no fetch IO was issued, the pointer is left set at NULL.
9537 *
9538 * On success, this function returns 0, otherwise it returns an appropriate
9539 * error code. On error the fetching IO is aborted and cleared before
9540 * returning from this function. Therefore, if we return `success', the
9541 * caller can assume that we have taken care of cleanup of fetch IOs.
9542 */
9543 static int
9544 l2arc_log_blk_read(l2arc_dev_t *dev,
9545 const l2arc_log_blkptr_t *this_lbp, const l2arc_log_blkptr_t *next_lbp,
9546 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb,
9547 zio_t *this_io, zio_t **next_io)
9548 {
9549 int err = 0;
9550 zio_cksum_t cksum;
9551 abd_t *abd = NULL;
9552 uint64_t asize;
9553
9554 ASSERT(this_lbp != NULL && next_lbp != NULL);
9555 ASSERT(this_lb != NULL && next_lb != NULL);
9556 ASSERT(next_io != NULL && *next_io == NULL);
9557 ASSERT(l2arc_log_blkptr_valid(dev, this_lbp));
9558
9559 /*
9560 * Check to see if we have issued the IO for this log block in a
9561 * previous run. If not, this is the first call, so issue it now.
9562 */
9563 if (this_io == NULL) {
9564 this_io = l2arc_log_blk_fetch(dev->l2ad_vdev, this_lbp,
9565 this_lb);
9566 }
9567
9568 /*
9569 * Peek to see if we can start issuing the next IO immediately.
9570 */
9571 if (l2arc_log_blkptr_valid(dev, next_lbp)) {
9572 /*
9573 * Start issuing IO for the next log block early - this
9574 * should help keep the L2ARC device busy while we
9575 * decompress and restore this log block.
9576 */
9577 *next_io = l2arc_log_blk_fetch(dev->l2ad_vdev, next_lbp,
9578 next_lb);
9579 }
9580
9581 /* Wait for the IO to read this log block to complete */
9582 if ((err = zio_wait(this_io)) != 0) {
9583 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors);
9584 zfs_dbgmsg("L2ARC IO error (%d) while reading log block, "
9585 "offset: %llu, vdev guid: %llu", err, this_lbp->lbp_daddr,
9586 dev->l2ad_vdev->vdev_guid);
9587 goto cleanup;
9588 }
9589
9590 /*
9591 * Make sure the buffer checks out.
9592 * L2BLK_GET_PSIZE returns aligned size for log blocks.
9593 */
9594 asize = L2BLK_GET_PSIZE((this_lbp)->lbp_prop);
9595 fletcher_4_native(this_lb, asize, NULL, &cksum);
9596 if (!ZIO_CHECKSUM_EQUAL(cksum, this_lbp->lbp_cksum)) {
9597 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_lb_errors);
9598 zfs_dbgmsg("L2ARC log block cksum failed, offset: %llu, "
9599 "vdev guid: %llu, l2ad_hand: %llu, l2ad_evict: %llu",
9600 this_lbp->lbp_daddr, dev->l2ad_vdev->vdev_guid,
9601 dev->l2ad_hand, dev->l2ad_evict);
9602 err = SET_ERROR(ECKSUM);
9603 goto cleanup;
9604 }
9605
9606 /* Now we can take our time decoding this buffer */
9607 switch (L2BLK_GET_COMPRESS((this_lbp)->lbp_prop)) {
9608 case ZIO_COMPRESS_OFF:
9609 break;
9610 case ZIO_COMPRESS_LZ4:
9611 abd = abd_alloc_for_io(asize, B_TRUE);
9612 abd_copy_from_buf_off(abd, this_lb, 0, asize);
9613 if ((err = zio_decompress_data(
9614 L2BLK_GET_COMPRESS((this_lbp)->lbp_prop),
9615 abd, this_lb, asize, sizeof (*this_lb))) != 0) {
9616 err = SET_ERROR(EINVAL);
9617 goto cleanup;
9618 }
9619 break;
9620 default:
9621 err = SET_ERROR(EINVAL);
9622 goto cleanup;
9623 }
9624 if (this_lb->lb_magic == BSWAP_64(L2ARC_LOG_BLK_MAGIC))
9625 byteswap_uint64_array(this_lb, sizeof (*this_lb));
9626 if (this_lb->lb_magic != L2ARC_LOG_BLK_MAGIC) {
9627 err = SET_ERROR(EINVAL);
9628 goto cleanup;
9629 }
9630 cleanup:
9631 /* Abort an in-flight fetch I/O in case of error */
9632 if (err != 0 && *next_io != NULL) {
9633 l2arc_log_blk_fetch_abort(*next_io);
9634 *next_io = NULL;
9635 }
9636 if (abd != NULL)
9637 abd_free(abd);
9638 return (err);
9639 }
9640
9641 /*
9642 * Restores the payload of a log block to ARC. This creates empty ARC hdr
9643 * entries which only contain an l2arc hdr, essentially restoring the
9644 * buffers to their L2ARC evicted state. This function also updates space
9645 * usage on the L2ARC vdev to make sure it tracks restored buffers.
9646 */
9647 static void
9648 l2arc_log_blk_restore(l2arc_dev_t *dev, const l2arc_log_blk_phys_t *lb,
9649 uint64_t lb_asize)
9650 {
9651 uint64_t size = 0, asize = 0;
9652 uint64_t log_entries = dev->l2ad_log_entries;
9653
9654 /*
9655 * Usually arc_adapt() is called only for data, not headers, but
9656 * since we may allocate significant amount of memory here, let ARC
9657 * grow its arc_c.
9658 */
9659 arc_adapt(log_entries * HDR_L2ONLY_SIZE, arc_l2c_only);
9660
9661 for (int i = log_entries - 1; i >= 0; i--) {
9662 /*
9663 * Restore goes in the reverse temporal direction to preserve
9664 * correct temporal ordering of buffers in the l2ad_buflist.
9665 * l2arc_hdr_restore also does a list_insert_tail instead of
9666 * list_insert_head on the l2ad_buflist:
9667 *
9668 * LIST l2ad_buflist LIST
9669 * HEAD <------ (time) ------ TAIL
9670 * direction +-----+-----+-----+-----+-----+ direction
9671 * of l2arc <== | buf | buf | buf | buf | buf | ===> of rebuild
9672 * fill +-----+-----+-----+-----+-----+
9673 * ^ ^
9674 * | |
9675 * | |
9676 * l2arc_feed_thread l2arc_rebuild
9677 * will place new bufs here restores bufs here
9678 *
9679 * During l2arc_rebuild() the device is not used by
9680 * l2arc_feed_thread() as dev->l2ad_rebuild is set to true.
9681 */
9682 size += L2BLK_GET_LSIZE((&lb->lb_entries[i])->le_prop);
9683 asize += vdev_psize_to_asize(dev->l2ad_vdev,
9684 L2BLK_GET_PSIZE((&lb->lb_entries[i])->le_prop));
9685 l2arc_hdr_restore(&lb->lb_entries[i], dev);
9686 }
9687
9688 /*
9689 * Record rebuild stats:
9690 * size Logical size of restored buffers in the L2ARC
9691 * asize Aligned size of restored buffers in the L2ARC
9692 */
9693 ARCSTAT_INCR(arcstat_l2_rebuild_size, size);
9694 ARCSTAT_INCR(arcstat_l2_rebuild_asize, asize);
9695 ARCSTAT_INCR(arcstat_l2_rebuild_bufs, log_entries);
9696 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_asize, lb_asize);
9697 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, asize / lb_asize);
9698 ARCSTAT_BUMP(arcstat_l2_rebuild_log_blks);
9699 }
9700
9701 /*
9702 * Restores a single ARC buf hdr from a log entry. The ARC buffer is put
9703 * into a state indicating that it has been evicted to L2ARC.
9704 */
9705 static void
9706 l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, l2arc_dev_t *dev)
9707 {
9708 arc_buf_hdr_t *hdr, *exists;
9709 kmutex_t *hash_lock;
9710 arc_buf_contents_t type = L2BLK_GET_TYPE((le)->le_prop);
9711 uint64_t asize;
9712
9713 /*
9714 * Do all the allocation before grabbing any locks, this lets us
9715 * sleep if memory is full and we don't have to deal with failed
9716 * allocations.
9717 */
9718 hdr = arc_buf_alloc_l2only(L2BLK_GET_LSIZE((le)->le_prop), type,
9719 dev, le->le_dva, le->le_daddr,
9720 L2BLK_GET_PSIZE((le)->le_prop), le->le_birth,
9721 L2BLK_GET_COMPRESS((le)->le_prop),
9722 L2BLK_GET_PROTECTED((le)->le_prop),
9723 L2BLK_GET_PREFETCH((le)->le_prop),
9724 L2BLK_GET_STATE((le)->le_prop));
9725 asize = vdev_psize_to_asize(dev->l2ad_vdev,
9726 L2BLK_GET_PSIZE((le)->le_prop));
9727
9728 /*
9729 * vdev_space_update() has to be called before arc_hdr_destroy() to
9730 * avoid underflow since the latter also calls vdev_space_update().
9731 */
9732 l2arc_hdr_arcstats_increment(hdr);
9733 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
9734
9735 mutex_enter(&dev->l2ad_mtx);
9736 list_insert_tail(&dev->l2ad_buflist, hdr);
9737 (void) zfs_refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
9738 mutex_exit(&dev->l2ad_mtx);
9739
9740 exists = buf_hash_insert(hdr, &hash_lock);
9741 if (exists) {
9742 /* Buffer was already cached, no need to restore it. */
9743 arc_hdr_destroy(hdr);
9744 /*
9745 * If the buffer is already cached, check whether it has
9746 * L2ARC metadata. If not, enter them and update the flag.
9747 * This is important is case of onlining a cache device, since
9748 * we previously evicted all L2ARC metadata from ARC.
9749 */
9750 if (!HDR_HAS_L2HDR(exists)) {
9751 arc_hdr_set_flags(exists, ARC_FLAG_HAS_L2HDR);
9752 exists->b_l2hdr.b_dev = dev;
9753 exists->b_l2hdr.b_daddr = le->le_daddr;
9754 exists->b_l2hdr.b_arcs_state =
9755 L2BLK_GET_STATE((le)->le_prop);
9756 mutex_enter(&dev->l2ad_mtx);
9757 list_insert_tail(&dev->l2ad_buflist, exists);
9758 (void) zfs_refcount_add_many(&dev->l2ad_alloc,
9759 arc_hdr_size(exists), exists);
9760 mutex_exit(&dev->l2ad_mtx);
9761 l2arc_hdr_arcstats_increment(exists);
9762 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
9763 }
9764 ARCSTAT_BUMP(arcstat_l2_rebuild_bufs_precached);
9765 }
9766
9767 mutex_exit(hash_lock);
9768 }
9769
9770 /*
9771 * Starts an asynchronous read IO to read a log block. This is used in log
9772 * block reconstruction to start reading the next block before we are done
9773 * decoding and reconstructing the current block, to keep the l2arc device
9774 * nice and hot with read IO to process.
9775 * The returned zio will contain newly allocated memory buffers for the IO
9776 * data which should then be freed by the caller once the zio is no longer
9777 * needed (i.e. due to it having completed). If you wish to abort this
9778 * zio, you should do so using l2arc_log_blk_fetch_abort, which takes
9779 * care of disposing of the allocated buffers correctly.
9780 */
9781 static zio_t *
9782 l2arc_log_blk_fetch(vdev_t *vd, const l2arc_log_blkptr_t *lbp,
9783 l2arc_log_blk_phys_t *lb)
9784 {
9785 uint32_t asize;
9786 zio_t *pio;
9787 l2arc_read_callback_t *cb;
9788
9789 /* L2BLK_GET_PSIZE returns aligned size for log blocks */
9790 asize = L2BLK_GET_PSIZE((lbp)->lbp_prop);
9791 ASSERT(asize <= sizeof (l2arc_log_blk_phys_t));
9792
9793 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), KM_SLEEP);
9794 cb->l2rcb_abd = abd_get_from_buf(lb, asize);
9795 pio = zio_root(vd->vdev_spa, l2arc_blk_fetch_done, cb,
9796 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE |
9797 ZIO_FLAG_DONT_RETRY);
9798 (void) zio_nowait(zio_read_phys(pio, vd, lbp->lbp_daddr, asize,
9799 cb->l2rcb_abd, ZIO_CHECKSUM_OFF, NULL, NULL,
9800 ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
9801 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE));
9802
9803 return (pio);
9804 }
9805
9806 /*
9807 * Aborts a zio returned from l2arc_log_blk_fetch and frees the data
9808 * buffers allocated for it.
9809 */
9810 static void
9811 l2arc_log_blk_fetch_abort(zio_t *zio)
9812 {
9813 (void) zio_wait(zio);
9814 }
9815
9816 /*
9817 * Creates a zio to update the device header on an l2arc device.
9818 */
9819 static void
9820 l2arc_dev_hdr_update(l2arc_dev_t *dev)
9821 {
9822 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
9823 const uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize;
9824 abd_t *abd;
9825 int err;
9826
9827 VERIFY(spa_config_held(dev->l2ad_spa, SCL_STATE_ALL, RW_READER));
9828
9829 l2dhdr->dh_magic = L2ARC_DEV_HDR_MAGIC;
9830 l2dhdr->dh_version = L2ARC_PERSISTENT_VERSION;
9831 l2dhdr->dh_spa_guid = spa_guid(dev->l2ad_vdev->vdev_spa);
9832 l2dhdr->dh_vdev_guid = dev->l2ad_vdev->vdev_guid;
9833 l2dhdr->dh_log_entries = dev->l2ad_log_entries;
9834 l2dhdr->dh_evict = dev->l2ad_evict;
9835 l2dhdr->dh_start = dev->l2ad_start;
9836 l2dhdr->dh_end = dev->l2ad_end;
9837 l2dhdr->dh_lb_asize = zfs_refcount_count(&dev->l2ad_lb_asize);
9838 l2dhdr->dh_lb_count = zfs_refcount_count(&dev->l2ad_lb_count);
9839 l2dhdr->dh_flags = 0;
9840 if (dev->l2ad_first)
9841 l2dhdr->dh_flags |= L2ARC_DEV_HDR_EVICT_FIRST;
9842
9843 abd = abd_get_from_buf(l2dhdr, l2dhdr_asize);
9844
9845 err = zio_wait(zio_write_phys(NULL, dev->l2ad_vdev,
9846 VDEV_LABEL_START_SIZE, l2dhdr_asize, abd, ZIO_CHECKSUM_LABEL, NULL,
9847 NULL, ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE));
9848
9849 abd_put(abd);
9850
9851 if (err != 0) {
9852 zfs_dbgmsg("L2ARC IO error (%d) while writing device header, "
9853 "vdev guid: %llu", err, dev->l2ad_vdev->vdev_guid);
9854 }
9855 }
9856
9857 /*
9858 * Commits a log block to the L2ARC device. This routine is invoked from
9859 * l2arc_write_buffers when the log block fills up.
9860 * This function allocates some memory to temporarily hold the serialized
9861 * buffer to be written. This is then released in l2arc_write_done.
9862 */
9863 static void
9864 l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, l2arc_write_callback_t *cb)
9865 {
9866 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
9867 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
9868 uint64_t psize, asize;
9869 zio_t *wzio;
9870 l2arc_lb_abd_buf_t *abd_buf;
9871 uint8_t *tmpbuf;
9872 l2arc_lb_ptr_buf_t *lb_ptr_buf;
9873
9874 VERIFY3S(dev->l2ad_log_ent_idx, ==, dev->l2ad_log_entries);
9875
9876 tmpbuf = zio_buf_alloc(sizeof (*lb));
9877 abd_buf = zio_buf_alloc(sizeof (*abd_buf));
9878 abd_buf->abd = abd_get_from_buf(lb, sizeof (*lb));
9879 lb_ptr_buf = kmem_zalloc(sizeof (l2arc_lb_ptr_buf_t), KM_SLEEP);
9880 lb_ptr_buf->lb_ptr = kmem_zalloc(sizeof (l2arc_log_blkptr_t), KM_SLEEP);
9881
9882 /* link the buffer into the block chain */
9883 lb->lb_prev_lbp = l2dhdr->dh_start_lbps[1];
9884 lb->lb_magic = L2ARC_LOG_BLK_MAGIC;
9885
9886 /*
9887 * l2arc_log_blk_commit() may be called multiple times during a single
9888 * l2arc_write_buffers() call. Save the allocated abd buffers in a list
9889 * so we can free them in l2arc_write_done() later on.
9890 */
9891 list_insert_tail(&cb->l2wcb_abd_list, abd_buf);
9892
9893 /* try to compress the buffer */
9894 psize = zio_compress_data(ZIO_COMPRESS_LZ4,
9895 abd_buf->abd, tmpbuf, sizeof (*lb));
9896
9897 /* a log block is never entirely zero */
9898 ASSERT(psize != 0);
9899 asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
9900 ASSERT(asize <= sizeof (*lb));
9901
9902 /*
9903 * Update the start log block pointer in the device header to point
9904 * to the log block we're about to write.
9905 */
9906 l2dhdr->dh_start_lbps[1] = l2dhdr->dh_start_lbps[0];
9907 l2dhdr->dh_start_lbps[0].lbp_daddr = dev->l2ad_hand;
9908 l2dhdr->dh_start_lbps[0].lbp_payload_asize =
9909 dev->l2ad_log_blk_payload_asize;
9910 l2dhdr->dh_start_lbps[0].lbp_payload_start =
9911 dev->l2ad_log_blk_payload_start;
9912 _NOTE(CONSTCOND)
9913 L2BLK_SET_LSIZE(
9914 (&l2dhdr->dh_start_lbps[0])->lbp_prop, sizeof (*lb));
9915 L2BLK_SET_PSIZE(
9916 (&l2dhdr->dh_start_lbps[0])->lbp_prop, asize);
9917 L2BLK_SET_CHECKSUM(
9918 (&l2dhdr->dh_start_lbps[0])->lbp_prop,
9919 ZIO_CHECKSUM_FLETCHER_4);
9920 if (asize < sizeof (*lb)) {
9921 /* compression succeeded */
9922 bzero(tmpbuf + psize, asize - psize);
9923 L2BLK_SET_COMPRESS(
9924 (&l2dhdr->dh_start_lbps[0])->lbp_prop,
9925 ZIO_COMPRESS_LZ4);
9926 } else {
9927 /* compression failed */
9928 bcopy(lb, tmpbuf, sizeof (*lb));
9929 L2BLK_SET_COMPRESS(
9930 (&l2dhdr->dh_start_lbps[0])->lbp_prop,
9931 ZIO_COMPRESS_OFF);
9932 }
9933
9934 /* checksum what we're about to write */
9935 fletcher_4_native(tmpbuf, asize, NULL,
9936 &l2dhdr->dh_start_lbps[0].lbp_cksum);
9937
9938 abd_put(abd_buf->abd);
9939
9940 /* perform the write itself */
9941 abd_buf->abd = abd_get_from_buf(tmpbuf, sizeof (*lb));
9942 abd_take_ownership_of_buf(abd_buf->abd, B_TRUE);
9943 wzio = zio_write_phys(pio, dev->l2ad_vdev, dev->l2ad_hand,
9944 asize, abd_buf->abd, ZIO_CHECKSUM_OFF, NULL, NULL,
9945 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE);
9946 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio);
9947 (void) zio_nowait(wzio);
9948
9949 dev->l2ad_hand += asize;
9950 /*
9951 * Include the committed log block's pointer in the list of pointers
9952 * to log blocks present in the L2ARC device.
9953 */
9954 bcopy(&l2dhdr->dh_start_lbps[0], lb_ptr_buf->lb_ptr,
9955 sizeof (l2arc_log_blkptr_t));
9956 mutex_enter(&dev->l2ad_mtx);
9957 list_insert_head(&dev->l2ad_lbptr_list, lb_ptr_buf);
9958 ARCSTAT_INCR(arcstat_l2_log_blk_asize, asize);
9959 ARCSTAT_BUMP(arcstat_l2_log_blk_count);
9960 zfs_refcount_add_many(&dev->l2ad_lb_asize, asize, lb_ptr_buf);
9961 zfs_refcount_add(&dev->l2ad_lb_count, lb_ptr_buf);
9962 mutex_exit(&dev->l2ad_mtx);
9963 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
9964
9965 /* bump the kstats */
9966 ARCSTAT_INCR(arcstat_l2_write_bytes, asize);
9967 ARCSTAT_BUMP(arcstat_l2_log_blk_writes);
9968 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_asize, asize);
9969 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio,
9970 dev->l2ad_log_blk_payload_asize / asize);
9971
9972 /* start a new log block */
9973 dev->l2ad_log_ent_idx = 0;
9974 dev->l2ad_log_blk_payload_asize = 0;
9975 dev->l2ad_log_blk_payload_start = 0;
9976 }
9977
9978 /*
9979 * Validates an L2ARC log block address to make sure that it can be read
9980 * from the provided L2ARC device.
9981 */
9982 boolean_t
9983 l2arc_log_blkptr_valid(l2arc_dev_t *dev, const l2arc_log_blkptr_t *lbp)
9984 {
9985 /* L2BLK_GET_PSIZE returns aligned size for log blocks */
9986 uint64_t asize = L2BLK_GET_PSIZE((lbp)->lbp_prop);
9987 uint64_t end = lbp->lbp_daddr + asize - 1;
9988 uint64_t start = lbp->lbp_payload_start;
9989 boolean_t evicted = B_FALSE;
9990
9991 /* BEGIN CSTYLED */
9992 /*
9993 * A log block is valid if all of the following conditions are true:
9994 * - it fits entirely (including its payload) between l2ad_start and
9995 * l2ad_end
9996 * - it has a valid size
9997 * - neither the log block itself nor part of its payload was evicted
9998 * by l2arc_evict():
9999 *
10000 * l2ad_hand l2ad_evict
10001 * | | lbp_daddr
10002 * | start | | end
10003 * | | | | |
10004 * V V V V V
10005 * l2ad_start ============================================ l2ad_end
10006 * --------------------------||||
10007 * ^ ^
10008 * | log block
10009 * payload
10010 */
10011 /* END CSTYLED */
10012 evicted =
10013 l2arc_range_check_overlap(start, end, dev->l2ad_hand) ||
10014 l2arc_range_check_overlap(start, end, dev->l2ad_evict) ||
10015 l2arc_range_check_overlap(dev->l2ad_hand, dev->l2ad_evict, start) ||
10016 l2arc_range_check_overlap(dev->l2ad_hand, dev->l2ad_evict, end);
10017
10018 return (start >= dev->l2ad_start && end <= dev->l2ad_end &&
10019 asize > 0 && asize <= sizeof (l2arc_log_blk_phys_t) &&
10020 (!evicted || dev->l2ad_first));
10021 }
10022
10023 /*
10024 * Inserts ARC buffer header `hdr' into the current L2ARC log block on
10025 * the device. The buffer being inserted must be present in L2ARC.
10026 * Returns B_TRUE if the L2ARC log block is full and needs to be committed
10027 * to L2ARC, or B_FALSE if it still has room for more ARC buffers.
10028 */
10029 static boolean_t
10030 l2arc_log_blk_insert(l2arc_dev_t *dev, const arc_buf_hdr_t *hdr)
10031 {
10032 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
10033 l2arc_log_ent_phys_t *le;
10034
10035 if (dev->l2ad_log_entries == 0)
10036 return (B_FALSE);
10037
10038 int index = dev->l2ad_log_ent_idx++;
10039
10040 ASSERT3S(index, <, dev->l2ad_log_entries);
10041 ASSERT(HDR_HAS_L2HDR(hdr));
10042
10043 le = &lb->lb_entries[index];
10044 bzero(le, sizeof (*le));
10045 le->le_dva = hdr->b_dva;
10046 le->le_birth = hdr->b_birth;
10047 le->le_daddr = hdr->b_l2hdr.b_daddr;
10048 if (index == 0)
10049 dev->l2ad_log_blk_payload_start = le->le_daddr;
10050 L2BLK_SET_LSIZE((le)->le_prop, HDR_GET_LSIZE(hdr));
10051 L2BLK_SET_PSIZE((le)->le_prop, HDR_GET_PSIZE(hdr));
10052 L2BLK_SET_COMPRESS((le)->le_prop, HDR_GET_COMPRESS(hdr));
10053 L2BLK_SET_TYPE((le)->le_prop, hdr->b_type);
10054 L2BLK_SET_PROTECTED((le)->le_prop, !!(HDR_PROTECTED(hdr)));
10055 L2BLK_SET_PREFETCH((le)->le_prop, !!(HDR_PREFETCH(hdr)));
10056 L2BLK_SET_STATE((le)->le_prop, hdr->b_l1hdr.b_state->arcs_state);
10057
10058 dev->l2ad_log_blk_payload_asize += vdev_psize_to_asize(dev->l2ad_vdev,
10059 HDR_GET_PSIZE(hdr));
10060
10061 return (dev->l2ad_log_ent_idx == dev->l2ad_log_entries);
10062 }
10063
10064 /*
10065 * Checks whether a given L2ARC device address sits in a time-sequential
10066 * range. The trick here is that the L2ARC is a rotary buffer, so we can't
10067 * just do a range comparison, we need to handle the situation in which the
10068 * range wraps around the end of the L2ARC device. Arguments:
10069 * bottom -- Lower end of the range to check (written to earlier).
10070 * top -- Upper end of the range to check (written to later).
10071 * check -- The address for which we want to determine if it sits in
10072 * between the top and bottom.
10073 *
10074 * The 3-way conditional below represents the following cases:
10075 *
10076 * bottom < top : Sequentially ordered case:
10077 * <check>--------+-------------------+
10078 * | (overlap here?) |
10079 * L2ARC dev V V
10080 * |---------------<bottom>============<top>--------------|
10081 *
10082 * bottom > top: Looped-around case:
10083 * <check>--------+------------------+
10084 * | (overlap here?) |
10085 * L2ARC dev V V
10086 * |===============<top>---------------<bottom>===========|
10087 * ^ ^
10088 * | (or here?) |
10089 * +---------------+---------<check>
10090 *
10091 * top == bottom : Just a single address comparison.
10092 */
10093 boolean_t
10094 l2arc_range_check_overlap(uint64_t bottom, uint64_t top, uint64_t check)
10095 {
10096 if (bottom < top)
10097 return (bottom <= check && check <= top);
10098 else if (bottom > top)
10099 return (check <= top || bottom <= check);
10100 else
10101 return (check == top);
10102 }