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) 2018, Joyent, Inc.
24 * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 * Copyright 2019 Nexenta Systems, Inc. All rights reserved.
27 */
28
29 /*
30 * DVA-based Adjustable Replacement Cache
31 *
32 * While much of the theory of operation used here is
33 * based on the self-tuning, low overhead replacement cache
34 * presented by Megiddo and Modha at FAST 2003, there are some
35 * significant differences:
36 *
37 * 1. The Megiddo and Modha model assumes any page is evictable.
38 * Pages in its cache cannot be "locked" into memory. This makes
39 * the eviction algorithm simple: evict the last page in the list.
40 * This also make the performance characteristics easy to reason
41 * about. Our cache is not so simple. At any given moment, some
42 * subset of the blocks in the cache are un-evictable because we
43 * have handed out a reference to them. Blocks are only evictable
44 * when there are no external references active. This makes
45 * eviction far more problematic: we choose to evict the evictable
46 * blocks that are the "lowest" in the list.
47 *
48 * There are times when it is not possible to evict the requested
49 * space. In these circumstances we are unable to adjust the cache
50 * size. To prevent the cache growing unbounded at these times we
51 * implement a "cache throttle" that slows the flow of new data
52 * into the cache until we can make space available.
53 *
54 * 2. The Megiddo and Modha model assumes a fixed cache size.
55 * Pages are evicted when the cache is full and there is a cache
56 * miss. Our model has a variable sized cache. It grows with
57 * high use, but also tries to react to memory pressure from the
58 * operating system: decreasing its size when system memory is
59 * tight.
60 *
61 * 3. The Megiddo and Modha model assumes a fixed page size. All
62 * elements of the cache are therefore exactly the same size. So
63 * when adjusting the cache size following a cache miss, its simply
64 * a matter of choosing a single page to evict. In our model, we
65 * have variable sized cache blocks (rangeing from 512 bytes to
66 * 128K bytes). We therefore choose a set of blocks to evict to make
67 * space for a cache miss that approximates as closely as possible
68 * the space used by the new block.
69 *
70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
71 * by N. Megiddo & D. Modha, FAST 2003
72 */
73
74 /*
75 * The locking model:
76 *
77 * A new reference to a cache buffer can be obtained in two
78 * ways: 1) via a hash table lookup using the DVA as a key,
79 * or 2) via one of the ARC lists. The arc_read() interface
80 * uses method 1, while the internal ARC algorithms for
81 * adjusting the cache use method 2. We therefore provide two
82 * types of locks: 1) the hash table lock array, and 2) the
83 * ARC list locks.
84 *
85 * Buffers do not have their own mutexes, rather they rely on the
86 * hash table mutexes for the bulk of their protection (i.e. most
87 * fields in the arc_buf_hdr_t are protected by these mutexes).
88 *
89 * buf_hash_find() returns the appropriate mutex (held) when it
90 * locates the requested buffer in the hash table. It returns
91 * NULL for the mutex if the buffer was not in the table.
92 *
93 * buf_hash_remove() expects the appropriate hash mutex to be
94 * already held before it is invoked.
95 *
96 * Each ARC state also has a mutex which is used to protect the
97 * buffer list associated with the state. When attempting to
98 * obtain a hash table lock while holding an ARC list lock you
99 * must use: mutex_tryenter() to avoid deadlock. Also note that
100 * the active state mutex must be held before the ghost state mutex.
101 *
102 * Note that the majority of the performance stats are manipulated
103 * with atomic operations.
104 *
105 * The L2ARC uses the l2ad_mtx on each vdev for the following:
106 *
107 * - L2ARC buflist creation
108 * - L2ARC buflist eviction
109 * - L2ARC write completion, which walks L2ARC buflists
110 * - ARC header destruction, as it removes from L2ARC buflists
111 * - ARC header release, as it removes from L2ARC buflists
112 */
113
114 /*
115 * ARC operation:
116 *
117 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
118 * This structure can point either to a block that is still in the cache or to
119 * one that is only accessible in an L2 ARC device, or it can provide
120 * information about a block that was recently evicted. If a block is
121 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
122 * information to retrieve it from the L2ARC device. This information is
123 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
124 * that is in this state cannot access the data directly.
125 *
126 * Blocks that are actively being referenced or have not been evicted
127 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
128 * the arc_buf_hdr_t that will point to the data block in memory. A block can
129 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
130 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
131 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd).
132 *
133 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the
134 * ability to store the physical data (b_pabd) associated with the DVA of the
135 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block,
136 * it will match its on-disk compression characteristics. This behavior can be
137 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
138 * compressed ARC functionality is disabled, the b_pabd will point to an
139 * uncompressed version of the on-disk data.
140 *
141 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each
142 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
143 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
144 * consumer. The ARC will provide references to this data and will keep it
145 * cached until it is no longer in use. The ARC caches only the L1ARC's physical
146 * data block and will evict any arc_buf_t that is no longer referenced. The
147 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
148 * "overhead_size" kstat.
149 *
150 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or
151 * compressed form. The typical case is that consumers will want uncompressed
152 * data, and when that happens a new data buffer is allocated where the data is
153 * decompressed for them to use. Currently the only consumer who wants
154 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it
155 * exists on disk. When this happens, the arc_buf_t's data buffer is shared
156 * with the arc_buf_hdr_t.
157 *
158 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
159 * first one is owned by a compressed send consumer (and therefore references
160 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be
161 * used by any other consumer (and has its own uncompressed copy of the data
162 * buffer).
163 *
164 * arc_buf_hdr_t
165 * +-----------+
166 * | fields |
167 * | common to |
168 * | L1- and |
169 * | L2ARC |
170 * +-----------+
171 * | l2arc_buf_hdr_t
172 * | |
173 * +-----------+
174 * | l1arc_buf_hdr_t
175 * | | arc_buf_t
176 * | b_buf +------------>+-----------+ arc_buf_t
177 * | b_pabd +-+ |b_next +---->+-----------+
178 * +-----------+ | |-----------| |b_next +-->NULL
179 * | |b_comp = T | +-----------+
180 * | |b_data +-+ |b_comp = F |
181 * | +-----------+ | |b_data +-+
182 * +->+------+ | +-----------+ |
183 * compressed | | | |
184 * data | |<--------------+ | uncompressed
185 * +------+ compressed, | data
186 * shared +-->+------+
187 * data | |
188 * | |
189 * +------+
190 *
191 * When a consumer reads a block, the ARC must first look to see if the
192 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
193 * arc_buf_t and either copies uncompressed data into a new data buffer from an
194 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a
195 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the
196 * hdr is compressed and the desired compression characteristics of the
197 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
198 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
199 * the last buffer in the hdr's b_buf list, however a shared compressed buf can
200 * be anywhere in the hdr's list.
201 *
202 * The diagram below shows an example of an uncompressed ARC hdr that is
203 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is
204 * the last element in the buf list):
205 *
206 * arc_buf_hdr_t
207 * +-----------+
208 * | |
209 * | |
210 * | |
211 * +-----------+
212 * l2arc_buf_hdr_t| |
213 * | |
214 * +-----------+
215 * l1arc_buf_hdr_t| |
216 * | | arc_buf_t (shared)
217 * | b_buf +------------>+---------+ arc_buf_t
218 * | | |b_next +---->+---------+
219 * | b_pabd +-+ |---------| |b_next +-->NULL
220 * +-----------+ | | | +---------+
221 * | |b_data +-+ | |
222 * | +---------+ | |b_data +-+
223 * +->+------+ | +---------+ |
224 * | | | |
225 * uncompressed | | | |
226 * data +------+ | |
227 * ^ +->+------+ |
228 * | uncompressed | | |
229 * | data | | |
230 * | +------+ |
231 * +---------------------------------+
232 *
233 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd
234 * since the physical block is about to be rewritten. The new data contents
235 * will be contained in the arc_buf_t. As the I/O pipeline performs the write,
236 * it may compress the data before writing it to disk. The ARC will be called
237 * with the transformed data and will bcopy the transformed on-disk block into
238 * a newly allocated b_pabd. Writes are always done into buffers which have
239 * either been loaned (and hence are new and don't have other readers) or
240 * buffers which have been released (and hence have their own hdr, if there
241 * were originally other readers of the buf's original hdr). This ensures that
242 * the ARC only needs to update a single buf and its hdr after a write occurs.
243 *
244 * When the L2ARC is in use, it will also take advantage of the b_pabd. The
245 * L2ARC will always write the contents of b_pabd to the L2ARC. This means
246 * that when compressed ARC is enabled that the L2ARC blocks are identical
247 * to the on-disk block in the main data pool. This provides a significant
248 * advantage since the ARC can leverage the bp's checksum when reading from the
249 * L2ARC to determine if the contents are valid. However, if the compressed
250 * ARC is disabled, then the L2ARC's block must be transformed to look
251 * like the physical block in the main data pool before comparing the
252 * checksum and determining its validity.
253 */
254
255 #include <sys/spa.h>
256 #include <sys/spa_impl.h>
257 #include <sys/zio.h>
258 #include <sys/spa_impl.h>
259 #include <sys/zio_compress.h>
260 #include <sys/zio_checksum.h>
261 #include <sys/zfs_context.h>
262 #include <sys/arc.h>
263 #include <sys/refcount.h>
264 #include <sys/vdev.h>
265 #include <sys/vdev_impl.h>
266 #include <sys/dsl_pool.h>
267 #include <sys/zio_checksum.h>
268 #include <sys/multilist.h>
269 #include <sys/abd.h>
270 #ifdef _KERNEL
271 #include <sys/vmsystm.h>
272 #include <vm/anon.h>
273 #include <sys/fs/swapnode.h>
274 #include <sys/dnlc.h>
275 #endif
276 #include <sys/callb.h>
277 #include <sys/kstat.h>
278 #include <zfs_fletcher.h>
279 #include <sys/byteorder.h>
280 #include <sys/spa_impl.h>
281
282 #ifndef _KERNEL
283 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
284 boolean_t arc_watch = B_FALSE;
285 int arc_procfd;
286 #endif
287
288 static kmutex_t arc_reclaim_lock;
289 static kcondvar_t arc_reclaim_thread_cv;
290 static boolean_t arc_reclaim_thread_exit;
291 static kcondvar_t arc_reclaim_waiters_cv;
292
293 uint_t arc_reduce_dnlc_percent = 3;
294
295 /*
296 * The number of headers to evict in arc_evict_state_impl() before
297 * dropping the sublist lock and evicting from another sublist. A lower
298 * value means we're more likely to evict the "correct" header (i.e. the
299 * oldest header in the arc state), but comes with higher overhead
300 * (i.e. more invocations of arc_evict_state_impl()).
301 */
302 int zfs_arc_evict_batch_limit = 10;
303
304 /* number of seconds before growing cache again */
305 static int arc_grow_retry = 60;
306
307 /* number of milliseconds before attempting a kmem-cache-reap */
308 static int arc_kmem_cache_reap_retry_ms = 1000;
309
310 /* shift of arc_c for calculating overflow limit in arc_get_data_impl */
311 int zfs_arc_overflow_shift = 8;
312
313 /* shift of arc_c for calculating both min and max arc_p */
314 static int arc_p_min_shift = 4;
315
316 /* log2(fraction of arc to reclaim) */
317 static int arc_shrink_shift = 7;
318
319 /*
320 * log2(fraction of ARC which must be free to allow growing).
321 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
322 * when reading a new block into the ARC, we will evict an equal-sized block
323 * from the ARC.
324 *
325 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
326 * we will still not allow it to grow.
327 */
328 int arc_no_grow_shift = 5;
329
330
331 /*
332 * minimum lifespan of a prefetch block in clock ticks
333 * (initialized in arc_init())
334 */
335 static int arc_min_prefetch_lifespan;
336
337 /*
338 * If this percent of memory is free, don't throttle.
339 */
340 int arc_lotsfree_percent = 10;
341
342 static int arc_dead;
343
344 /*
345 * The arc has filled available memory and has now warmed up.
346 */
347 static boolean_t arc_warm;
348
349 /*
350 * log2 fraction of the zio arena to keep free.
351 */
352 int arc_zio_arena_free_shift = 2;
353
354 /*
355 * These tunables are for performance analysis.
356 */
357 uint64_t zfs_arc_max;
358 uint64_t zfs_arc_min;
359 uint64_t zfs_arc_meta_limit = 0;
360 uint64_t zfs_arc_meta_min = 0;
361 uint64_t zfs_arc_ddt_limit = 0;
362 /*
363 * Tunable to control "dedup ceiling"
364 * Possible values:
365 * DDT_NO_LIMIT - default behaviour, ie no ceiling
366 * DDT_LIMIT_TO_ARC - stop DDT growth if DDT is bigger than it's "ARC space"
367 * DDT_LIMIT_TO_L2ARC - stop DDT growth when DDT size is bigger than the
368 * L2ARC DDT dev(s) for that pool
369 */
370 zfs_ddt_limit_t zfs_ddt_limit_type = DDT_LIMIT_TO_ARC;
371 /*
372 * Alternative to the above way of controlling "dedup ceiling":
373 * Stop DDT growth when in core DDTs size is above the below tunable.
374 * This tunable overrides the zfs_ddt_limit_type tunable.
375 */
376 uint64_t zfs_ddt_byte_ceiling = 0;
377 boolean_t zfs_arc_segregate_ddt = B_TRUE;
378 int zfs_arc_grow_retry = 0;
379 int zfs_arc_shrink_shift = 0;
380 int zfs_arc_p_min_shift = 0;
381 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
382
383 /* Tuneable, default is 64, which is essentially arbitrary */
384 int zfs_flush_ntasks = 64;
385
386 boolean_t zfs_compressed_arc_enabled = B_TRUE;
387
388 /*
389 * Note that buffers can be in one of 6 states:
390 * ARC_anon - anonymous (discussed below)
391 * ARC_mru - recently used, currently cached
392 * ARC_mru_ghost - recentely used, no longer in cache
393 * ARC_mfu - frequently used, currently cached
394 * ARC_mfu_ghost - frequently used, no longer in cache
395 * ARC_l2c_only - exists in L2ARC but not other states
396 * When there are no active references to the buffer, they are
397 * are linked onto a list in one of these arc states. These are
398 * the only buffers that can be evicted or deleted. Within each
399 * state there are multiple lists, one for meta-data and one for
400 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
401 * etc.) is tracked separately so that it can be managed more
402 * explicitly: favored over data, limited explicitly.
403 *
404 * Anonymous buffers are buffers that are not associated with
405 * a DVA. These are buffers that hold dirty block copies
406 * before they are written to stable storage. By definition,
407 * they are "ref'd" and are considered part of arc_mru
408 * that cannot be freed. Generally, they will aquire a DVA
409 * as they are written and migrate onto the arc_mru list.
410 *
411 * The ARC_l2c_only state is for buffers that are in the second
412 * level ARC but no longer in any of the ARC_m* lists. The second
413 * level ARC itself may also contain buffers that are in any of
414 * the ARC_m* states - meaning that a buffer can exist in two
415 * places. The reason for the ARC_l2c_only state is to keep the
416 * buffer header in the hash table, so that reads that hit the
417 * second level ARC benefit from these fast lookups.
418 */
419
420 typedef struct arc_state {
421 /*
422 * list of evictable buffers
423 */
424 multilist_t *arcs_list[ARC_BUFC_NUMTYPES];
425 /*
426 * total amount of evictable data in this state
427 */
428 refcount_t arcs_esize[ARC_BUFC_NUMTYPES];
429 /*
430 * total amount of data in this state; this includes: evictable,
431 * non-evictable, ARC_BUFC_DATA, ARC_BUFC_METADATA and ARC_BUFC_DDT.
432 * ARC_BUFC_DDT list is only populated when zfs_arc_segregate_ddt is
433 * true.
434 */
435 refcount_t arcs_size;
436 } arc_state_t;
437
438 /*
439 * We loop through these in l2arc_write_buffers() starting from
440 * PRIORITY_MFU_DDT until we reach PRIORITY_NUMTYPES or the buffer that we
441 * will be writing to L2ARC dev gets full.
442 */
443 enum l2arc_priorities {
444 PRIORITY_MFU_DDT,
445 PRIORITY_MRU_DDT,
446 PRIORITY_MFU_META,
447 PRIORITY_MRU_META,
448 PRIORITY_MFU_DATA,
449 PRIORITY_MRU_DATA,
450 PRIORITY_NUMTYPES,
451 };
452
453 /* The 6 states: */
454 static arc_state_t ARC_anon;
455 static arc_state_t ARC_mru;
456 static arc_state_t ARC_mru_ghost;
457 static arc_state_t ARC_mfu;
458 static arc_state_t ARC_mfu_ghost;
459 static arc_state_t ARC_l2c_only;
460
461 typedef struct arc_stats {
462 kstat_named_t arcstat_hits;
463 kstat_named_t arcstat_ddt_hits;
464 kstat_named_t arcstat_misses;
465 kstat_named_t arcstat_demand_data_hits;
466 kstat_named_t arcstat_demand_data_misses;
467 kstat_named_t arcstat_demand_metadata_hits;
468 kstat_named_t arcstat_demand_metadata_misses;
469 kstat_named_t arcstat_demand_ddt_hits;
470 kstat_named_t arcstat_demand_ddt_misses;
471 kstat_named_t arcstat_prefetch_data_hits;
472 kstat_named_t arcstat_prefetch_data_misses;
473 kstat_named_t arcstat_prefetch_metadata_hits;
474 kstat_named_t arcstat_prefetch_metadata_misses;
475 kstat_named_t arcstat_prefetch_ddt_hits;
476 kstat_named_t arcstat_prefetch_ddt_misses;
477 kstat_named_t arcstat_mru_hits;
478 kstat_named_t arcstat_mru_ghost_hits;
479 kstat_named_t arcstat_mfu_hits;
480 kstat_named_t arcstat_mfu_ghost_hits;
481 kstat_named_t arcstat_deleted;
482 /*
483 * Number of buffers that could not be evicted because the hash lock
484 * was held by another thread. The lock may not necessarily be held
485 * by something using the same buffer, since hash locks are shared
486 * by multiple buffers.
487 */
488 kstat_named_t arcstat_mutex_miss;
489 /*
490 * Number of buffers skipped when updating the access state due to the
491 * header having already been released after acquiring the hash lock.
492 */
493 kstat_named_t arcstat_access_skip;
494 /*
495 * Number of buffers skipped because they have I/O in progress, are
496 * indirect prefetch buffers that have not lived long enough, or are
497 * not from the spa we're trying to evict from.
498 */
499 kstat_named_t arcstat_evict_skip;
500 /*
501 * Number of times arc_evict_state() was unable to evict enough
502 * buffers to reach it's target amount.
503 */
504 kstat_named_t arcstat_evict_not_enough;
505 kstat_named_t arcstat_evict_l2_cached;
506 kstat_named_t arcstat_evict_l2_eligible;
507 kstat_named_t arcstat_evict_l2_ineligible;
508 kstat_named_t arcstat_evict_l2_skip;
509 kstat_named_t arcstat_hash_elements;
510 kstat_named_t arcstat_hash_elements_max;
511 kstat_named_t arcstat_hash_collisions;
512 kstat_named_t arcstat_hash_chains;
513 kstat_named_t arcstat_hash_chain_max;
514 kstat_named_t arcstat_p;
515 kstat_named_t arcstat_c;
516 kstat_named_t arcstat_c_min;
517 kstat_named_t arcstat_c_max;
518 kstat_named_t arcstat_size;
519 /*
520 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd.
521 * Note that the compressed bytes may match the uncompressed bytes
522 * if the block is either not compressed or compressed arc is disabled.
523 */
524 kstat_named_t arcstat_compressed_size;
525 /*
526 * Uncompressed size of the data stored in b_pabd. If compressed
527 * arc is disabled then this value will be identical to the stat
528 * above.
529 */
530 kstat_named_t arcstat_uncompressed_size;
531 /*
532 * Number of bytes stored in all the arc_buf_t's. This is classified
533 * as "overhead" since this data is typically short-lived and will
534 * be evicted from the arc when it becomes unreferenced unless the
535 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level
536 * values have been set (see comment in dbuf.c for more information).
537 */
538 kstat_named_t arcstat_overhead_size;
539 /*
540 * Number of bytes consumed by internal ARC structures necessary
541 * for tracking purposes; these structures are not actually
542 * backed by ARC buffers. This includes arc_buf_hdr_t structures
543 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
544 * caches), and arc_buf_t structures (allocated via arc_buf_t
545 * cache).
546 */
547 kstat_named_t arcstat_hdr_size;
548 /*
549 * Number of bytes consumed by ARC buffers of type equal to
550 * ARC_BUFC_DATA. This is generally consumed by buffers backing
551 * on disk user data (e.g. plain file contents).
552 */
553 kstat_named_t arcstat_data_size;
554 /*
555 * Number of bytes consumed by ARC buffers of type equal to
556 * ARC_BUFC_METADATA. This is generally consumed by buffers
557 * backing on disk data that is used for internal ZFS
558 * structures (e.g. ZAP, dnode, indirect blocks, etc).
559 */
560 kstat_named_t arcstat_metadata_size;
561 /*
562 * Number of bytes consumed by ARC buffers of type equal to
563 * ARC_BUFC_DDT. This is consumed by buffers backing on disk data
564 * that is used to store DDT (ZAP, ddt stats).
565 * Only used if zfs_arc_segregate_ddt is true.
566 */
567 kstat_named_t arcstat_ddt_size;
568 /*
569 * Number of bytes consumed by various buffers and structures
570 * not actually backed with ARC buffers. This includes bonus
571 * buffers (allocated directly via zio_buf_* functions),
572 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
573 * cache), and dnode_t structures (allocated via dnode_t cache).
574 */
575 kstat_named_t arcstat_other_size;
576 /*
577 * Total number of bytes consumed by ARC buffers residing in the
578 * arc_anon state. This includes *all* buffers in the arc_anon
579 * state; e.g. data, metadata, evictable, and unevictable buffers
580 * are all included in this value.
581 */
582 kstat_named_t arcstat_anon_size;
583 /*
584 * Number of bytes consumed by ARC buffers that meet the
585 * following criteria: backing buffers of type ARC_BUFC_DATA,
586 * residing in the arc_anon state, and are eligible for eviction
587 * (e.g. have no outstanding holds on the buffer).
588 */
589 kstat_named_t arcstat_anon_evictable_data;
590 /*
591 * Number of bytes consumed by ARC buffers that meet the
592 * following criteria: backing buffers of type ARC_BUFC_METADATA,
593 * residing in the arc_anon state, and are eligible for eviction
594 * (e.g. have no outstanding holds on the buffer).
595 */
596 kstat_named_t arcstat_anon_evictable_metadata;
597 /*
598 * Number of bytes consumed by ARC buffers that meet the
599 * following criteria: backing buffers of type ARC_BUFC_DDT,
600 * residing in the arc_anon state, and are eligible for eviction
601 * Only used if zfs_arc_segregate_ddt is true.
602 */
603 kstat_named_t arcstat_anon_evictable_ddt;
604 /*
605 * Total number of bytes consumed by ARC buffers residing in the
606 * arc_mru state. This includes *all* buffers in the arc_mru
607 * state; e.g. data, metadata, evictable, and unevictable buffers
608 * are all included in this value.
609 */
610 kstat_named_t arcstat_mru_size;
611 /*
612 * Number of bytes consumed by ARC buffers that meet the
613 * following criteria: backing buffers of type ARC_BUFC_DATA,
614 * residing in the arc_mru state, and are eligible for eviction
615 * (e.g. have no outstanding holds on the buffer).
616 */
617 kstat_named_t arcstat_mru_evictable_data;
618 /*
619 * Number of bytes consumed by ARC buffers that meet the
620 * following criteria: backing buffers of type ARC_BUFC_METADATA,
621 * residing in the arc_mru state, and are eligible for eviction
622 * (e.g. have no outstanding holds on the buffer).
623 */
624 kstat_named_t arcstat_mru_evictable_metadata;
625 /*
626 * Number of bytes consumed by ARC buffers that meet the
627 * following criteria: backing buffers of type ARC_BUFC_DDT,
628 * residing in the arc_mru state, and are eligible for eviction
629 * (e.g. have no outstanding holds on the buffer).
630 * Only used if zfs_arc_segregate_ddt is true.
631 */
632 kstat_named_t arcstat_mru_evictable_ddt;
633 /*
634 * Total number of bytes that *would have been* consumed by ARC
635 * buffers in the arc_mru_ghost state. The key thing to note
636 * here, is the fact that this size doesn't actually indicate
637 * RAM consumption. The ghost lists only consist of headers and
638 * don't actually have ARC buffers linked off of these headers.
639 * Thus, *if* the headers had associated ARC buffers, these
640 * buffers *would have* consumed this number of bytes.
641 */
642 kstat_named_t arcstat_mru_ghost_size;
643 /*
644 * Number of bytes that *would have been* consumed by ARC
645 * buffers that are eligible for eviction, of type
646 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
647 */
648 kstat_named_t arcstat_mru_ghost_evictable_data;
649 /*
650 * Number of bytes that *would have been* consumed by ARC
651 * buffers that are eligible for eviction, of type
652 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
653 */
654 kstat_named_t arcstat_mru_ghost_evictable_metadata;
655 /*
656 * Number of bytes that *would have been* consumed by ARC
657 * buffers that are eligible for eviction, of type
658 * ARC_BUFC_DDT, and linked off the arc_mru_ghost state.
659 * Only used if zfs_arc_segregate_ddt is true.
660 */
661 kstat_named_t arcstat_mru_ghost_evictable_ddt;
662 /*
663 * Total number of bytes consumed by ARC buffers residing in the
664 * arc_mfu state. This includes *all* buffers in the arc_mfu
665 * state; e.g. data, metadata, evictable, and unevictable buffers
666 * are all included in this value.
667 */
668 kstat_named_t arcstat_mfu_size;
669 /*
670 * Number of bytes consumed by ARC buffers that are eligible for
671 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
672 * state.
673 */
674 kstat_named_t arcstat_mfu_evictable_data;
675 /*
676 * Number of bytes consumed by ARC buffers that are eligible for
677 * eviction, of type ARC_BUFC_METADATA, and reside in the
678 * arc_mfu state.
679 */
680 kstat_named_t arcstat_mfu_evictable_metadata;
681 /*
682 * Number of bytes consumed by ARC buffers that are eligible for
683 * eviction, of type ARC_BUFC_DDT, and reside in the
684 * arc_mfu state.
685 * Only used if zfs_arc_segregate_ddt is true.
686 */
687 kstat_named_t arcstat_mfu_evictable_ddt;
688 /*
689 * Total number of bytes that *would have been* consumed by ARC
690 * buffers in the arc_mfu_ghost state. See the comment above
691 * arcstat_mru_ghost_size for more details.
692 */
693 kstat_named_t arcstat_mfu_ghost_size;
694 /*
695 * Number of bytes that *would have been* consumed by ARC
696 * buffers that are eligible for eviction, of type
697 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
698 */
699 kstat_named_t arcstat_mfu_ghost_evictable_data;
700 /*
701 * Number of bytes that *would have been* consumed by ARC
702 * buffers that are eligible for eviction, of type
703 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
704 */
705 kstat_named_t arcstat_mfu_ghost_evictable_metadata;
706 /*
707 * Number of bytes that *would have been* consumed by ARC
708 * buffers that are eligible for eviction, of type
709 * ARC_BUFC_DDT, and linked off the arc_mru_ghost state.
710 * Only used if zfs_arc_segregate_ddt is true.
711 */
712 kstat_named_t arcstat_mfu_ghost_evictable_ddt;
713 kstat_named_t arcstat_l2_hits;
714 kstat_named_t arcstat_l2_ddt_hits;
715 kstat_named_t arcstat_l2_misses;
716 kstat_named_t arcstat_l2_feeds;
717 kstat_named_t arcstat_l2_rw_clash;
718 kstat_named_t arcstat_l2_read_bytes;
719 kstat_named_t arcstat_l2_ddt_read_bytes;
720 kstat_named_t arcstat_l2_write_bytes;
721 kstat_named_t arcstat_l2_ddt_write_bytes;
722 kstat_named_t arcstat_l2_writes_sent;
723 kstat_named_t arcstat_l2_writes_done;
724 kstat_named_t arcstat_l2_writes_error;
725 kstat_named_t arcstat_l2_writes_lock_retry;
726 kstat_named_t arcstat_l2_evict_lock_retry;
727 kstat_named_t arcstat_l2_evict_reading;
728 kstat_named_t arcstat_l2_evict_l1cached;
729 kstat_named_t arcstat_l2_free_on_write;
730 kstat_named_t arcstat_l2_abort_lowmem;
731 kstat_named_t arcstat_l2_cksum_bad;
732 kstat_named_t arcstat_l2_io_error;
733 kstat_named_t arcstat_l2_lsize;
734 kstat_named_t arcstat_l2_psize;
735 kstat_named_t arcstat_l2_hdr_size;
736 kstat_named_t arcstat_l2_log_blk_writes;
737 kstat_named_t arcstat_l2_log_blk_avg_size;
738 kstat_named_t arcstat_l2_data_to_meta_ratio;
739 kstat_named_t arcstat_l2_rebuild_successes;
740 kstat_named_t arcstat_l2_rebuild_abort_unsupported;
741 kstat_named_t arcstat_l2_rebuild_abort_io_errors;
742 kstat_named_t arcstat_l2_rebuild_abort_cksum_errors;
743 kstat_named_t arcstat_l2_rebuild_abort_loop_errors;
744 kstat_named_t arcstat_l2_rebuild_abort_lowmem;
745 kstat_named_t arcstat_l2_rebuild_size;
746 kstat_named_t arcstat_l2_rebuild_bufs;
747 kstat_named_t arcstat_l2_rebuild_bufs_precached;
748 kstat_named_t arcstat_l2_rebuild_psize;
749 kstat_named_t arcstat_l2_rebuild_log_blks;
750 kstat_named_t arcstat_memory_throttle_count;
751 kstat_named_t arcstat_meta_used;
752 kstat_named_t arcstat_meta_limit;
753 kstat_named_t arcstat_meta_max;
754 kstat_named_t arcstat_meta_min;
755 kstat_named_t arcstat_ddt_limit;
756 kstat_named_t arcstat_sync_wait_for_async;
757 kstat_named_t arcstat_demand_hit_predictive_prefetch;
758 } arc_stats_t;
759
760 static arc_stats_t arc_stats = {
761 { "hits", KSTAT_DATA_UINT64 },
762 { "ddt_hits", KSTAT_DATA_UINT64 },
763 { "misses", KSTAT_DATA_UINT64 },
764 { "demand_data_hits", KSTAT_DATA_UINT64 },
765 { "demand_data_misses", KSTAT_DATA_UINT64 },
766 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
767 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
768 { "demand_ddt_hits", KSTAT_DATA_UINT64 },
769 { "demand_ddt_misses", KSTAT_DATA_UINT64 },
770 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
771 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
772 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
773 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
774 { "prefetch_ddt_hits", KSTAT_DATA_UINT64 },
775 { "prefetch_ddt_misses", KSTAT_DATA_UINT64 },
776 { "mru_hits", KSTAT_DATA_UINT64 },
777 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
778 { "mfu_hits", KSTAT_DATA_UINT64 },
779 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
780 { "deleted", KSTAT_DATA_UINT64 },
781 { "mutex_miss", KSTAT_DATA_UINT64 },
782 { "access_skip", KSTAT_DATA_UINT64 },
783 { "evict_skip", KSTAT_DATA_UINT64 },
784 { "evict_not_enough", KSTAT_DATA_UINT64 },
785 { "evict_l2_cached", KSTAT_DATA_UINT64 },
786 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
787 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
788 { "evict_l2_skip", KSTAT_DATA_UINT64 },
789 { "hash_elements", KSTAT_DATA_UINT64 },
790 { "hash_elements_max", KSTAT_DATA_UINT64 },
791 { "hash_collisions", KSTAT_DATA_UINT64 },
792 { "hash_chains", KSTAT_DATA_UINT64 },
793 { "hash_chain_max", KSTAT_DATA_UINT64 },
794 { "p", KSTAT_DATA_UINT64 },
795 { "c", KSTAT_DATA_UINT64 },
796 { "c_min", KSTAT_DATA_UINT64 },
797 { "c_max", KSTAT_DATA_UINT64 },
798 { "size", KSTAT_DATA_UINT64 },
799 { "compressed_size", KSTAT_DATA_UINT64 },
800 { "uncompressed_size", KSTAT_DATA_UINT64 },
801 { "overhead_size", KSTAT_DATA_UINT64 },
802 { "hdr_size", KSTAT_DATA_UINT64 },
803 { "data_size", KSTAT_DATA_UINT64 },
804 { "metadata_size", KSTAT_DATA_UINT64 },
805 { "ddt_size", KSTAT_DATA_UINT64 },
806 { "other_size", KSTAT_DATA_UINT64 },
807 { "anon_size", KSTAT_DATA_UINT64 },
808 { "anon_evictable_data", KSTAT_DATA_UINT64 },
809 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
810 { "anon_evictable_ddt", KSTAT_DATA_UINT64 },
811 { "mru_size", KSTAT_DATA_UINT64 },
812 { "mru_evictable_data", KSTAT_DATA_UINT64 },
813 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
814 { "mru_evictable_ddt", KSTAT_DATA_UINT64 },
815 { "mru_ghost_size", KSTAT_DATA_UINT64 },
816 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
817 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
818 { "mru_ghost_evictable_ddt", KSTAT_DATA_UINT64 },
819 { "mfu_size", KSTAT_DATA_UINT64 },
820 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
821 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
822 { "mfu_evictable_ddt", KSTAT_DATA_UINT64 },
823 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
824 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
825 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
826 { "mfu_ghost_evictable_ddt", KSTAT_DATA_UINT64 },
827 { "l2_hits", KSTAT_DATA_UINT64 },
828 { "l2_ddt_hits", KSTAT_DATA_UINT64 },
829 { "l2_misses", KSTAT_DATA_UINT64 },
830 { "l2_feeds", KSTAT_DATA_UINT64 },
831 { "l2_rw_clash", KSTAT_DATA_UINT64 },
832 { "l2_read_bytes", KSTAT_DATA_UINT64 },
833 { "l2_ddt_read_bytes", KSTAT_DATA_UINT64 },
834 { "l2_write_bytes", KSTAT_DATA_UINT64 },
835 { "l2_ddt_write_bytes", KSTAT_DATA_UINT64 },
836 { "l2_writes_sent", KSTAT_DATA_UINT64 },
837 { "l2_writes_done", KSTAT_DATA_UINT64 },
838 { "l2_writes_error", KSTAT_DATA_UINT64 },
839 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
840 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
841 { "l2_evict_reading", KSTAT_DATA_UINT64 },
842 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
843 { "l2_free_on_write", KSTAT_DATA_UINT64 },
844 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
845 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
846 { "l2_io_error", KSTAT_DATA_UINT64 },
847 { "l2_size", KSTAT_DATA_UINT64 },
848 { "l2_asize", KSTAT_DATA_UINT64 },
849 { "l2_hdr_size", KSTAT_DATA_UINT64 },
850 { "l2_log_blk_writes", KSTAT_DATA_UINT64 },
851 { "l2_log_blk_avg_size", KSTAT_DATA_UINT64 },
852 { "l2_data_to_meta_ratio", KSTAT_DATA_UINT64 },
853 { "l2_rebuild_successes", KSTAT_DATA_UINT64 },
854 { "l2_rebuild_unsupported", KSTAT_DATA_UINT64 },
855 { "l2_rebuild_io_errors", KSTAT_DATA_UINT64 },
856 { "l2_rebuild_cksum_errors", KSTAT_DATA_UINT64 },
857 { "l2_rebuild_loop_errors", KSTAT_DATA_UINT64 },
858 { "l2_rebuild_lowmem", KSTAT_DATA_UINT64 },
859 { "l2_rebuild_size", KSTAT_DATA_UINT64 },
860 { "l2_rebuild_bufs", KSTAT_DATA_UINT64 },
861 { "l2_rebuild_bufs_precached", KSTAT_DATA_UINT64 },
862 { "l2_rebuild_psize", KSTAT_DATA_UINT64 },
863 { "l2_rebuild_log_blks", KSTAT_DATA_UINT64 },
864 { "memory_throttle_count", KSTAT_DATA_UINT64 },
865 { "arc_meta_used", KSTAT_DATA_UINT64 },
866 { "arc_meta_limit", KSTAT_DATA_UINT64 },
867 { "arc_meta_max", KSTAT_DATA_UINT64 },
868 { "arc_meta_min", KSTAT_DATA_UINT64 },
869 { "arc_ddt_limit", KSTAT_DATA_UINT64 },
870 { "sync_wait_for_async", KSTAT_DATA_UINT64 },
871 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
872 };
873
874 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
875
876 #define ARCSTAT_INCR(stat, val) \
877 atomic_add_64(&arc_stats.stat.value.ui64, (val))
878
879 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
880 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
881
882 #define ARCSTAT_MAX(stat, val) { \
883 uint64_t m; \
884 while ((val) > (m = arc_stats.stat.value.ui64) && \
885 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
886 continue; \
887 }
888
889 #define ARCSTAT_MAXSTAT(stat) \
890 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
891
892 /*
893 * We define a macro to allow ARC hits/misses to be easily broken down by
894 * two separate conditions, giving a total of four different subtypes for
895 * each of hits and misses (so eight statistics total).
896 */
897 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
898 if (cond1) { \
899 if (cond2) { \
900 ARCSTAT_BUMP(arcstat_##stat1##_##stat##_##stat2); \
901 } else { \
902 ARCSTAT_BUMP(arcstat_##stat1##_##stat##_##notstat2); \
903 } \
904 } else { \
905 if (cond2) { \
906 ARCSTAT_BUMP(arcstat_##notstat1##_##stat##_##stat2); \
907 } else { \
908 ARCSTAT_BUMP(arcstat_##notstat1##_##stat##_##notstat2);\
909 } \
910 }
911
912 /*
913 * This macro allows us to use kstats as floating averages. Each time we
914 * update this kstat, we first factor it and the update value by
915 * ARCSTAT_AVG_FACTOR to shrink the new value's contribution to the overall
916 * average. This macro assumes that integer loads and stores are atomic, but
917 * is not safe for multiple writers updating the kstat in parallel (only the
918 * last writer's update will remain).
919 */
920 #define ARCSTAT_F_AVG_FACTOR 3
921 #define ARCSTAT_F_AVG(stat, value) \
922 do { \
923 uint64_t x = ARCSTAT(stat); \
924 x = x - x / ARCSTAT_F_AVG_FACTOR + \
925 (value) / ARCSTAT_F_AVG_FACTOR; \
926 ARCSTAT(stat) = x; \
927 _NOTE(CONSTCOND) \
928 } while (0)
929
930 kstat_t *arc_ksp;
931 static arc_state_t *arc_anon;
932 static arc_state_t *arc_mru;
933 static arc_state_t *arc_mru_ghost;
934 static arc_state_t *arc_mfu;
935 static arc_state_t *arc_mfu_ghost;
936 static arc_state_t *arc_l2c_only;
937
938 /*
939 * There are several ARC variables that are critical to export as kstats --
940 * but we don't want to have to grovel around in the kstat whenever we wish to
941 * manipulate them. For these variables, we therefore define them to be in
942 * terms of the statistic variable. This assures that we are not introducing
943 * the possibility of inconsistency by having shadow copies of the variables,
944 * while still allowing the code to be readable.
945 */
946 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
947 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
948 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
949 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
950 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
951 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
952 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
953 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
954 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
955 #define arc_ddt_size ARCSTAT(arcstat_ddt_size) /* ddt size in arc */
956 #define arc_ddt_limit ARCSTAT(arcstat_ddt_limit) /* ddt in arc size limit */
957
958 /*
959 * Used int zio.c to optionally keep DDT cached in ARC
960 */
961 uint64_t const *arc_ddt_evict_threshold;
962
963 /* compressed size of entire arc */
964 #define arc_compressed_size ARCSTAT(arcstat_compressed_size)
965 /* uncompressed size of entire arc */
966 #define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size)
967 /* number of bytes in the arc from arc_buf_t's */
968 #define arc_overhead_size ARCSTAT(arcstat_overhead_size)
969
970
971 static int arc_no_grow; /* Don't try to grow cache size */
972 static uint64_t arc_tempreserve;
973 static uint64_t arc_loaned_bytes;
974
975 typedef struct arc_callback arc_callback_t;
976
977 struct arc_callback {
978 void *acb_private;
979 arc_done_func_t *acb_done;
980 arc_buf_t *acb_buf;
981 boolean_t acb_compressed;
982 zio_t *acb_zio_dummy;
983 arc_callback_t *acb_next;
984 };
985
986 typedef struct arc_write_callback arc_write_callback_t;
987
988 struct arc_write_callback {
989 void *awcb_private;
990 arc_done_func_t *awcb_ready;
991 arc_done_func_t *awcb_children_ready;
992 arc_done_func_t *awcb_physdone;
993 arc_done_func_t *awcb_done;
994 arc_buf_t *awcb_buf;
995 };
996
997 /*
998 * ARC buffers are separated into multiple structs as a memory saving measure:
999 * - Common fields struct, always defined, and embedded within it:
1000 * - L2-only fields, always allocated but undefined when not in L2ARC
1001 * - L1-only fields, only allocated when in L1ARC
1002 *
1003 * Buffer in L1 Buffer only in L2
1004 * +------------------------+ +------------------------+
1005 * | arc_buf_hdr_t | | arc_buf_hdr_t |
1006 * | | | |
1007 * | | | |
1008 * | | | |
1009 * +------------------------+ +------------------------+
1010 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
1011 * | (undefined if L1-only) | | |
1012 * +------------------------+ +------------------------+
1013 * | l1arc_buf_hdr_t |
1014 * | |
1015 * | |
1016 * | |
1017 * | |
1018 * +------------------------+
1019 *
1020 * Because it's possible for the L2ARC to become extremely large, we can wind
1021 * up eating a lot of memory in L2ARC buffer headers, so the size of a header
1022 * is minimized by only allocating the fields necessary for an L1-cached buffer
1023 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
1024 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
1025 * words in pointers. arc_hdr_realloc() is used to switch a header between
1026 * these two allocation states.
1027 */
1028 typedef struct l1arc_buf_hdr {
1029 kmutex_t b_freeze_lock;
1030 #ifdef ZFS_DEBUG
1031 /*
1032 * Used for debugging with kmem_flags - by allocating and freeing
1033 * b_thawed when the buffer is thawed, we get a record of the stack
1034 * trace that thawed it.
1035 */
1036 void *b_thawed;
1037 #endif
1038
1039 /* number of krrp tasks using this buffer */
1040 uint64_t b_krrp;
1041
1042 arc_buf_t *b_buf;
1043 uint32_t b_bufcnt;
1044 /* for waiting on writes to complete */
1045 kcondvar_t b_cv;
1046 uint8_t b_byteswap;
1047
1048 /* protected by arc state mutex */
1049 arc_state_t *b_state;
1050 multilist_node_t b_arc_node;
1051
1052 /* updated atomically */
1053 clock_t b_arc_access;
1054
1055 /* self protecting */
1056 refcount_t b_refcnt;
1057
1058 arc_callback_t *b_acb;
1059 abd_t *b_pabd;
1060 } l1arc_buf_hdr_t;
1061
1062 typedef struct l2arc_dev l2arc_dev_t;
1063
1064 typedef struct l2arc_buf_hdr {
1065 /* protected by arc_buf_hdr mutex */
1066 l2arc_dev_t *b_dev; /* L2ARC device */
1067 uint64_t b_daddr; /* disk address, offset byte */
1068
1069 list_node_t b_l2node;
1070 } l2arc_buf_hdr_t;
1071
1072 struct arc_buf_hdr {
1073 /* protected by hash lock */
1074 dva_t b_dva;
1075 uint64_t b_birth;
1076
1077 /*
1078 * Even though this checksum is only set/verified when a buffer is in
1079 * the L1 cache, it needs to be in the set of common fields because it
1080 * must be preserved from the time before a buffer is written out to
1081 * L2ARC until after it is read back in.
1082 */
1083 zio_cksum_t *b_freeze_cksum;
1084
1085 arc_buf_contents_t b_type;
1086 arc_buf_hdr_t *b_hash_next;
1087 arc_flags_t b_flags;
1088
1089 /*
1090 * This field stores the size of the data buffer after
1091 * compression, and is set in the arc's zio completion handlers.
1092 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes).
1093 *
1094 * While the block pointers can store up to 32MB in their psize
1095 * field, we can only store up to 32MB minus 512B. This is due
1096 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e.
1097 * a field of zeros represents 512B in the bp). We can't use a
1098 * bias of 1 since we need to reserve a psize of zero, here, to
1099 * represent holes and embedded blocks.
1100 *
1101 * This isn't a problem in practice, since the maximum size of a
1102 * buffer is limited to 16MB, so we never need to store 32MB in
1103 * this field. Even in the upstream illumos code base, the
1104 * maximum size of a buffer is limited to 16MB.
1105 */
1106 uint16_t b_psize;
1107
1108 /*
1109 * This field stores the size of the data buffer before
1110 * compression, and cannot change once set. It is in units
1111 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes)
1112 */
1113 uint16_t b_lsize; /* immutable */
1114 uint64_t b_spa; /* immutable */
1115
1116 /* L2ARC fields. Undefined when not in L2ARC. */
1117 l2arc_buf_hdr_t b_l2hdr;
1118 /* L1ARC fields. Undefined when in l2arc_only state */
1119 l1arc_buf_hdr_t b_l1hdr;
1120 };
1121
1122 #define GHOST_STATE(state) \
1123 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
1124 (state) == arc_l2c_only)
1125
1126 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
1127 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
1128 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
1129 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
1130 #define HDR_COMPRESSION_ENABLED(hdr) \
1131 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
1132
1133 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
1134 #define HDR_L2_READING(hdr) \
1135 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
1136 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
1137 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
1138 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
1139 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
1140 #define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
1141
1142 #define HDR_ISTYPE_DDT(hdr) \
1143 ((hdr)->b_flags & ARC_FLAG_BUFC_DDT)
1144 #define HDR_ISTYPE_METADATA(hdr) \
1145 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
1146 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr) && \
1147 !HDR_ISTYPE_DDT(hdr))
1148
1149 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
1150 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
1151
1152 /* For storing compression mode in b_flags */
1153 #define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
1154
1155 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
1156 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
1157 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
1158 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
1159
1160 #define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
1161 #define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
1162 #define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
1163
1164 /*
1165 * Other sizes
1166 */
1167
1168 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
1169 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
1170
1171 /*
1172 * Hash table routines
1173 */
1174
1175 struct ht_table {
1176 arc_buf_hdr_t *hdr;
1177 kmutex_t lock;
1178 };
1179
1180 typedef struct buf_hash_table {
1181 uint64_t ht_mask;
1182 struct ht_table *ht_table;
1183 } buf_hash_table_t;
1184
1185 #pragma align 64(buf_hash_table)
1186 static buf_hash_table_t buf_hash_table;
1187
1188 #define BUF_HASH_INDEX(spa, dva, birth) \
1189 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
1190 #define BUF_HASH_LOCK(idx) (&buf_hash_table.ht_table[idx].lock)
1191 #define HDR_LOCK(hdr) \
1192 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
1193
1194 uint64_t zfs_crc64_table[256];
1195
1196 /*
1197 * Level 2 ARC
1198 */
1199
1200 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
1201 #define L2ARC_HEADROOM 2 /* num of writes */
1202 /*
1203 * If we discover during ARC scan any buffers to be compressed, we boost
1204 * our headroom for the next scanning cycle by this percentage multiple.
1205 */
1206 #define L2ARC_HEADROOM_BOOST 200
1207 #define L2ARC_FEED_SECS 1 /* caching interval secs */
1208 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
1209
1210 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
1211 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
1212
1213 /* L2ARC Performance Tunables */
1214 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
1215 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
1216 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
1217 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
1218 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
1219 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
1220 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
1221 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
1222 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
1223
1224 static list_t L2ARC_dev_list; /* device list */
1225 static list_t *l2arc_dev_list; /* device list pointer */
1226 static kmutex_t l2arc_dev_mtx; /* device list mutex */
1227 static l2arc_dev_t *l2arc_dev_last; /* last device used */
1228 static l2arc_dev_t *l2arc_ddt_dev_last; /* last DDT device used */
1229 static list_t L2ARC_free_on_write; /* free after write buf list */
1230 static list_t *l2arc_free_on_write; /* free after write list ptr */
1231 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
1232 static uint64_t l2arc_ndev; /* number of devices */
1233
1234 typedef struct l2arc_read_callback {
1235 arc_buf_hdr_t *l2rcb_hdr; /* read header */
1236 blkptr_t l2rcb_bp; /* original blkptr */
1237 zbookmark_phys_t l2rcb_zb; /* original bookmark */
1238 int l2rcb_flags; /* original flags */
1239 abd_t *l2rcb_abd; /* temporary buffer */
1240 } l2arc_read_callback_t;
1241
1242 typedef struct l2arc_write_callback {
1243 l2arc_dev_t *l2wcb_dev; /* device info */
1244 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
1245 list_t l2wcb_log_blk_buflist; /* in-flight log blocks */
1246 } l2arc_write_callback_t;
1247
1248 typedef struct l2arc_data_free {
1249 /* protected by l2arc_free_on_write_mtx */
1250 abd_t *l2df_abd;
1251 size_t l2df_size;
1252 arc_buf_contents_t l2df_type;
1253 list_node_t l2df_list_node;
1254 } l2arc_data_free_t;
1255
1256 static kmutex_t l2arc_feed_thr_lock;
1257 static kcondvar_t l2arc_feed_thr_cv;
1258 static uint8_t l2arc_thread_exit;
1259
1260 static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *);
1261 static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
1262 static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *);
1263 static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *);
1264 static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
1265 static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag);
1266 static void arc_hdr_free_pabd(arc_buf_hdr_t *);
1267 static void arc_hdr_alloc_pabd(arc_buf_hdr_t *);
1268 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
1269 static boolean_t arc_is_overflowing();
1270 static void arc_buf_watch(arc_buf_t *);
1271 static l2arc_dev_t *l2arc_vdev_get(vdev_t *vd);
1272
1273 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
1274 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
1275 static arc_buf_contents_t arc_flags_to_bufc(uint32_t);
1276 static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1277 static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1278
1279 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
1280 static void l2arc_read_done(zio_t *);
1281
1282 static void
1283 arc_update_hit_stat(arc_buf_hdr_t *hdr, boolean_t hit)
1284 {
1285 boolean_t pf = !HDR_PREFETCH(hdr);
1286 switch (arc_buf_type(hdr)) {
1287 case ARC_BUFC_DATA:
1288 ARCSTAT_CONDSTAT(pf, demand, prefetch, hit, hits, misses, data);
1289 break;
1290 case ARC_BUFC_METADATA:
1291 ARCSTAT_CONDSTAT(pf, demand, prefetch, hit, hits, misses,
1292 metadata);
1293 break;
1294 case ARC_BUFC_DDT:
1295 ARCSTAT_CONDSTAT(pf, demand, prefetch, hit, hits, misses, ddt);
1296 break;
1297 default:
1298 break;
1299 }
1300 }
1301
1302 enum {
1303 L2ARC_DEV_HDR_EVICT_FIRST = (1 << 0) /* mirror of l2ad_first */
1304 };
1305
1306 /*
1307 * Pointer used in persistent L2ARC (for pointing to log blocks & ARC buffers).
1308 */
1309 typedef struct l2arc_log_blkptr {
1310 uint64_t lbp_daddr; /* device address of log */
1311 /*
1312 * lbp_prop is the same format as the blk_prop in blkptr_t:
1313 * * logical size (in sectors)
1314 * * physical size (in sectors)
1315 * * checksum algorithm (used for lbp_cksum)
1316 * * object type & level (unused for now)
1317 */
1318 uint64_t lbp_prop;
1319 zio_cksum_t lbp_cksum; /* fletcher4 of log */
1320 } l2arc_log_blkptr_t;
1321
1322 /*
1323 * The persistent L2ARC device header.
1324 * Byte order of magic determines whether 64-bit bswap of fields is necessary.
1325 */
1326 typedef struct l2arc_dev_hdr_phys {
1327 uint64_t dh_magic; /* L2ARC_DEV_HDR_MAGIC_Vx */
1328 zio_cksum_t dh_self_cksum; /* fletcher4 of fields below */
1329
1330 /*
1331 * Global L2ARC device state and metadata.
1332 */
1333 uint64_t dh_spa_guid;
1334 uint64_t dh_alloc_space; /* vdev space alloc status */
1335 uint64_t dh_flags; /* l2arc_dev_hdr_flags_t */
1336
1337 /*
1338 * Start of log block chain. [0] -> newest log, [1] -> one older (used
1339 * for initiating prefetch).
1340 */
1341 l2arc_log_blkptr_t dh_start_lbps[2];
1342
1343 const uint64_t dh_pad[44]; /* pad to 512 bytes */
1344 } l2arc_dev_hdr_phys_t;
1345 CTASSERT(sizeof (l2arc_dev_hdr_phys_t) == SPA_MINBLOCKSIZE);
1346
1347 /*
1348 * A single ARC buffer header entry in a l2arc_log_blk_phys_t.
1349 */
1350 typedef struct l2arc_log_ent_phys {
1351 dva_t le_dva; /* dva of buffer */
1352 uint64_t le_birth; /* birth txg of buffer */
1353 zio_cksum_t le_freeze_cksum;
1354 /*
1355 * le_prop is the same format as the blk_prop in blkptr_t:
1356 * * logical size (in sectors)
1357 * * physical size (in sectors)
1358 * * checksum algorithm (used for b_freeze_cksum)
1359 * * object type & level (used to restore arc_buf_contents_t)
1360 */
1361 uint64_t le_prop;
1362 uint64_t le_daddr; /* buf location on l2dev */
1363 const uint64_t le_pad[7]; /* resv'd for future use */
1364 } l2arc_log_ent_phys_t;
1365
1366 /*
1367 * These design limits give us the following metadata overhead (before
1368 * compression):
1369 * avg_blk_sz overhead
1370 * 1k 12.51 %
1371 * 2k 6.26 %
1372 * 4k 3.13 %
1373 * 8k 1.56 %
1374 * 16k 0.78 %
1375 * 32k 0.39 %
1376 * 64k 0.20 %
1377 * 128k 0.10 %
1378 * Compression should be able to sequeeze these down by about a factor of 2x.
1379 */
1380 #define L2ARC_LOG_BLK_SIZE (128 * 1024) /* 128k */
1381 #define L2ARC_LOG_BLK_HEADER_LEN (128)
1382 #define L2ARC_LOG_BLK_ENTRIES /* 1023 entries */ \
1383 ((L2ARC_LOG_BLK_SIZE - L2ARC_LOG_BLK_HEADER_LEN) / \
1384 sizeof (l2arc_log_ent_phys_t))
1385 /*
1386 * Maximum amount of data in an l2arc log block (used to terminate rebuilding
1387 * before we hit the write head and restore potentially corrupted blocks).
1388 */
1389 #define L2ARC_LOG_BLK_MAX_PAYLOAD_SIZE \
1390 (SPA_MAXBLOCKSIZE * L2ARC_LOG_BLK_ENTRIES)
1391 /*
1392 * For the persistency and rebuild algorithms to operate reliably we need
1393 * the L2ARC device to at least be able to hold 3 full log blocks (otherwise
1394 * excessive log block looping might confuse the log chain end detection).
1395 * Under normal circumstances this is not a problem, since this is somewhere
1396 * around only 400 MB.
1397 */
1398 #define L2ARC_PERSIST_MIN_SIZE (3 * L2ARC_LOG_BLK_MAX_PAYLOAD_SIZE)
1399
1400 /*
1401 * A log block of up to 1023 ARC buffer log entries, chained into the
1402 * persistent L2ARC metadata linked list. Byte order of magic determines
1403 * whether 64-bit bswap of fields is necessary.
1404 */
1405 typedef struct l2arc_log_blk_phys {
1406 /* Header - see L2ARC_LOG_BLK_HEADER_LEN above */
1407 uint64_t lb_magic; /* L2ARC_LOG_BLK_MAGIC */
1408 l2arc_log_blkptr_t lb_back2_lbp; /* back 2 steps in chain */
1409 uint64_t lb_pad[9]; /* resv'd for future use */
1410 /* Payload */
1411 l2arc_log_ent_phys_t lb_entries[L2ARC_LOG_BLK_ENTRIES];
1412 } l2arc_log_blk_phys_t;
1413
1414 CTASSERT(sizeof (l2arc_log_blk_phys_t) == L2ARC_LOG_BLK_SIZE);
1415 CTASSERT(offsetof(l2arc_log_blk_phys_t, lb_entries) -
1416 offsetof(l2arc_log_blk_phys_t, lb_magic) == L2ARC_LOG_BLK_HEADER_LEN);
1417
1418 /*
1419 * These structures hold in-flight l2arc_log_blk_phys_t's as they're being
1420 * written to the L2ARC device. They may be compressed, hence the uint8_t[].
1421 */
1422 typedef struct l2arc_log_blk_buf {
1423 uint8_t lbb_log_blk[sizeof (l2arc_log_blk_phys_t)];
1424 list_node_t lbb_node;
1425 } l2arc_log_blk_buf_t;
1426
1427 /* Macros for the manipulation fields in the blk_prop format of blkptr_t */
1428 #define BLKPROP_GET_LSIZE(_obj, _field) \
1429 BF64_GET_SB((_obj)->_field, 0, 16, SPA_MINBLOCKSHIFT, 1)
1430 #define BLKPROP_SET_LSIZE(_obj, _field, x) \
1431 BF64_SET_SB((_obj)->_field, 0, 16, SPA_MINBLOCKSHIFT, 1, x)
1432 #define BLKPROP_GET_PSIZE(_obj, _field) \
1433 BF64_GET_SB((_obj)->_field, 16, 16, SPA_MINBLOCKSHIFT, 0)
1434 #define BLKPROP_SET_PSIZE(_obj, _field, x) \
1435 BF64_SET_SB((_obj)->_field, 16, 16, SPA_MINBLOCKSHIFT, 0, x)
1436 #define BLKPROP_GET_COMPRESS(_obj, _field) \
1437 BF64_GET((_obj)->_field, 32, 7)
1438 #define BLKPROP_SET_COMPRESS(_obj, _field, x) \
1439 BF64_SET((_obj)->_field, 32, 7, x)
1440 #define BLKPROP_GET_ARC_COMPRESS(_obj, _field) \
1441 BF64_GET((_obj)->_field, 39, 1)
1442 #define BLKPROP_SET_ARC_COMPRESS(_obj, _field, x) \
1443 BF64_SET((_obj)->_field, 39, 1, x)
1444 #define BLKPROP_GET_CHECKSUM(_obj, _field) \
1445 BF64_GET((_obj)->_field, 40, 8)
1446 #define BLKPROP_SET_CHECKSUM(_obj, _field, x) \
1447 BF64_SET((_obj)->_field, 40, 8, x)
1448 #define BLKPROP_GET_TYPE(_obj, _field) \
1449 BF64_GET((_obj)->_field, 48, 8)
1450 #define BLKPROP_SET_TYPE(_obj, _field, x) \
1451 BF64_SET((_obj)->_field, 48, 8, x)
1452
1453 /* Macros for manipulating a l2arc_log_blkptr_t->lbp_prop field */
1454 #define LBP_GET_LSIZE(_add) BLKPROP_GET_LSIZE(_add, lbp_prop)
1455 #define LBP_SET_LSIZE(_add, x) BLKPROP_SET_LSIZE(_add, lbp_prop, x)
1456 #define LBP_GET_PSIZE(_add) BLKPROP_GET_PSIZE(_add, lbp_prop)
1457 #define LBP_SET_PSIZE(_add, x) BLKPROP_SET_PSIZE(_add, lbp_prop, x)
1458 #define LBP_GET_COMPRESS(_add) BLKPROP_GET_COMPRESS(_add, lbp_prop)
1459 #define LBP_SET_COMPRESS(_add, x) BLKPROP_SET_COMPRESS(_add, lbp_prop, x)
1460 #define LBP_GET_CHECKSUM(_add) BLKPROP_GET_CHECKSUM(_add, lbp_prop)
1461 #define LBP_SET_CHECKSUM(_add, x) BLKPROP_SET_CHECKSUM(_add, lbp_prop, x)
1462 #define LBP_GET_TYPE(_add) BLKPROP_GET_TYPE(_add, lbp_prop)
1463 #define LBP_SET_TYPE(_add, x) BLKPROP_SET_TYPE(_add, lbp_prop, x)
1464
1465 /* Macros for manipulating a l2arc_log_ent_phys_t->le_prop field */
1466 #define LE_GET_LSIZE(_le) BLKPROP_GET_LSIZE(_le, le_prop)
1467 #define LE_SET_LSIZE(_le, x) BLKPROP_SET_LSIZE(_le, le_prop, x)
1468 #define LE_GET_PSIZE(_le) BLKPROP_GET_PSIZE(_le, le_prop)
1469 #define LE_SET_PSIZE(_le, x) BLKPROP_SET_PSIZE(_le, le_prop, x)
1470 #define LE_GET_COMPRESS(_le) BLKPROP_GET_COMPRESS(_le, le_prop)
1471 #define LE_SET_COMPRESS(_le, x) BLKPROP_SET_COMPRESS(_le, le_prop, x)
1472 #define LE_GET_ARC_COMPRESS(_le) BLKPROP_GET_ARC_COMPRESS(_le, le_prop)
1473 #define LE_SET_ARC_COMPRESS(_le, x) BLKPROP_SET_ARC_COMPRESS(_le, le_prop, x)
1474 #define LE_GET_CHECKSUM(_le) BLKPROP_GET_CHECKSUM(_le, le_prop)
1475 #define LE_SET_CHECKSUM(_le, x) BLKPROP_SET_CHECKSUM(_le, le_prop, x)
1476 #define LE_GET_TYPE(_le) BLKPROP_GET_TYPE(_le, le_prop)
1477 #define LE_SET_TYPE(_le, x) BLKPROP_SET_TYPE(_le, le_prop, x)
1478
1479 #define PTR_SWAP(x, y) \
1480 do { \
1481 void *tmp = (x);\
1482 x = y; \
1483 y = tmp; \
1484 _NOTE(CONSTCOND)\
1485 } while (0)
1486
1487 /*
1488 * Sadly, after compressed ARC integration older kernels would panic
1489 * when trying to rebuild persistent L2ARC created by the new code.
1490 */
1491 #define L2ARC_DEV_HDR_MAGIC_V1 0x4c32415243763031LLU /* ASCII: "L2ARCv01" */
1492 #define L2ARC_LOG_BLK_MAGIC 0x4c4f47424c4b4844LLU /* ASCII: "LOGBLKHD" */
1493
1494 /*
1495 * Performance tuning of L2ARC persistency:
1496 *
1497 * l2arc_rebuild_enabled : Controls whether L2ARC device adds (either at
1498 * pool import or when adding one manually later) will attempt
1499 * to rebuild L2ARC buffer contents. In special circumstances,
1500 * the administrator may want to set this to B_FALSE, if they
1501 * are having trouble importing a pool or attaching an L2ARC
1502 * device (e.g. the L2ARC device is slow to read in stored log
1503 * metadata, or the metadata has become somehow
1504 * fragmented/unusable).
1505 */
1506 boolean_t l2arc_rebuild_enabled = B_TRUE;
1507
1508 /* L2ARC persistency rebuild control routines. */
1509 static void l2arc_dev_rebuild_start(l2arc_dev_t *dev);
1510 static int l2arc_rebuild(l2arc_dev_t *dev);
1511
1512 /* L2ARC persistency read I/O routines. */
1513 static int l2arc_dev_hdr_read(l2arc_dev_t *dev);
1514 static int l2arc_log_blk_read(l2arc_dev_t *dev,
1515 const l2arc_log_blkptr_t *this_lp, const l2arc_log_blkptr_t *next_lp,
1516 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb,
1517 uint8_t *this_lb_buf, uint8_t *next_lb_buf,
1518 zio_t *this_io, zio_t **next_io);
1519 static zio_t *l2arc_log_blk_prefetch(vdev_t *vd,
1520 const l2arc_log_blkptr_t *lp, uint8_t *lb_buf);
1521 static void l2arc_log_blk_prefetch_abort(zio_t *zio);
1522
1523 /* L2ARC persistency block restoration routines. */
1524 static void l2arc_log_blk_restore(l2arc_dev_t *dev, uint64_t load_guid,
1525 const l2arc_log_blk_phys_t *lb, uint64_t lb_psize);
1526 static void l2arc_hdr_restore(const l2arc_log_ent_phys_t *le,
1527 l2arc_dev_t *dev, uint64_t guid);
1528
1529 /* L2ARC persistency write I/O routines. */
1530 static void l2arc_dev_hdr_update(l2arc_dev_t *dev, zio_t *pio);
1531 static void l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio,
1532 l2arc_write_callback_t *cb);
1533
1534 /* L2ARC persistency auxilliary routines. */
1535 static boolean_t l2arc_log_blkptr_valid(l2arc_dev_t *dev,
1536 const l2arc_log_blkptr_t *lp);
1537 static void l2arc_dev_hdr_checksum(const l2arc_dev_hdr_phys_t *hdr,
1538 zio_cksum_t *cksum);
1539 static boolean_t l2arc_log_blk_insert(l2arc_dev_t *dev,
1540 const arc_buf_hdr_t *ab);
1541 static inline boolean_t l2arc_range_check_overlap(uint64_t bottom,
1542 uint64_t top, uint64_t check);
1543
1544 /*
1545 * L2ARC Internals
1546 */
1547 struct l2arc_dev {
1548 vdev_t *l2ad_vdev; /* vdev */
1549 spa_t *l2ad_spa; /* spa */
1550 uint64_t l2ad_hand; /* next write location */
1551 uint64_t l2ad_start; /* first addr on device */
1552 uint64_t l2ad_end; /* last addr on device */
1553 boolean_t l2ad_first; /* first sweep through */
1554 boolean_t l2ad_writing; /* currently writing */
1555 kmutex_t l2ad_mtx; /* lock for buffer list */
1556 list_t l2ad_buflist; /* buffer list */
1557 list_node_t l2ad_node; /* device list node */
1558 refcount_t l2ad_alloc; /* allocated bytes */
1559 l2arc_dev_hdr_phys_t *l2ad_dev_hdr; /* persistent device header */
1560 uint64_t l2ad_dev_hdr_asize; /* aligned hdr size */
1561 l2arc_log_blk_phys_t l2ad_log_blk; /* currently open log block */
1562 int l2ad_log_ent_idx; /* index into cur log blk */
1563 /* number of bytes in current log block's payload */
1564 uint64_t l2ad_log_blk_payload_asize;
1565 /* flag indicating whether a rebuild is scheduled or is going on */
1566 boolean_t l2ad_rebuild;
1567 boolean_t l2ad_rebuild_cancel;
1568 kt_did_t l2ad_rebuild_did;
1569 };
1570
1571 static inline uint64_t
1572 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
1573 {
1574 uint8_t *vdva = (uint8_t *)dva;
1575 uint64_t crc = -1ULL;
1576 int i;
1577
1578 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
1579
1580 for (i = 0; i < sizeof (dva_t); i++)
1581 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
1582
1583 crc ^= (spa>>8) ^ birth;
1584
1585 return (crc);
1586 }
1587
1588 #define HDR_EMPTY(hdr) \
1589 ((hdr)->b_dva.dva_word[0] == 0 && \
1590 (hdr)->b_dva.dva_word[1] == 0)
1591
1592 #define HDR_EQUAL(spa, dva, birth, hdr) \
1593 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
1594 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
1595 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
1596
1597 static void
1598 buf_discard_identity(arc_buf_hdr_t *hdr)
1599 {
1600 hdr->b_dva.dva_word[0] = 0;
1601 hdr->b_dva.dva_word[1] = 0;
1602 hdr->b_birth = 0;
1603 }
1604
1605 static arc_buf_hdr_t *
1606 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
1607 {
1608 const dva_t *dva = BP_IDENTITY(bp);
1609 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
1610 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
1611 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1612 arc_buf_hdr_t *hdr;
1613
1614 mutex_enter(hash_lock);
1615 for (hdr = buf_hash_table.ht_table[idx].hdr; hdr != NULL;
1616 hdr = hdr->b_hash_next) {
1617 if (HDR_EQUAL(spa, dva, birth, hdr)) {
1618 *lockp = hash_lock;
1619 return (hdr);
1620 }
1621 }
1622 mutex_exit(hash_lock);
1623 *lockp = NULL;
1624 return (NULL);
1625 }
1626
1627 /*
1628 * Insert an entry into the hash table. If there is already an element
1629 * equal to elem in the hash table, then the already existing element
1630 * will be returned and the new element will not be inserted.
1631 * Otherwise returns NULL.
1632 * If lockp == NULL, the caller is assumed to already hold the hash lock.
1633 */
1634 static arc_buf_hdr_t *
1635 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
1636 {
1637 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1638 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1639 arc_buf_hdr_t *fhdr;
1640 uint32_t i;
1641
1642 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
1643 ASSERT(hdr->b_birth != 0);
1644 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1645
1646 if (lockp != NULL) {
1647 *lockp = hash_lock;
1648 mutex_enter(hash_lock);
1649 } else {
1650 ASSERT(MUTEX_HELD(hash_lock));
1651 }
1652
1653 for (fhdr = buf_hash_table.ht_table[idx].hdr, i = 0; fhdr != NULL;
1654 fhdr = fhdr->b_hash_next, i++) {
1655 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
1656 return (fhdr);
1657 }
1658
1659 hdr->b_hash_next = buf_hash_table.ht_table[idx].hdr;
1660 buf_hash_table.ht_table[idx].hdr = hdr;
1661 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1662
1663 /* collect some hash table performance data */
1664 if (i > 0) {
1665 ARCSTAT_BUMP(arcstat_hash_collisions);
1666 if (i == 1)
1667 ARCSTAT_BUMP(arcstat_hash_chains);
1668
1669 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1670 }
1671
1672 ARCSTAT_BUMP(arcstat_hash_elements);
1673 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1674
1675 return (NULL);
1676 }
1677
1678 static void
1679 buf_hash_remove(arc_buf_hdr_t *hdr)
1680 {
1681 arc_buf_hdr_t *fhdr, **hdrp;
1682 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1683
1684 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1685 ASSERT(HDR_IN_HASH_TABLE(hdr));
1686
1687 hdrp = &buf_hash_table.ht_table[idx].hdr;
1688 while ((fhdr = *hdrp) != hdr) {
1689 ASSERT3P(fhdr, !=, NULL);
1690 hdrp = &fhdr->b_hash_next;
1691 }
1692 *hdrp = hdr->b_hash_next;
1693 hdr->b_hash_next = NULL;
1694 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1695
1696 /* collect some hash table performance data */
1697 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1698
1699 if (buf_hash_table.ht_table[idx].hdr &&
1700 buf_hash_table.ht_table[idx].hdr->b_hash_next == NULL)
1701 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1702 }
1703
1704 /*
1705 * Global data structures and functions for the buf kmem cache.
1706 */
1707 static kmem_cache_t *hdr_full_cache;
1708 static kmem_cache_t *hdr_l2only_cache;
1709 static kmem_cache_t *buf_cache;
1710
1711 static void
1712 buf_fini(void)
1713 {
1714 int i;
1715
1716 for (i = 0; i < buf_hash_table.ht_mask + 1; i++)
1717 mutex_destroy(&buf_hash_table.ht_table[i].lock);
1718 kmem_free(buf_hash_table.ht_table,
1719 (buf_hash_table.ht_mask + 1) * sizeof (struct ht_table));
1720 kmem_cache_destroy(hdr_full_cache);
1721 kmem_cache_destroy(hdr_l2only_cache);
1722 kmem_cache_destroy(buf_cache);
1723 }
1724
1725 /*
1726 * Constructor callback - called when the cache is empty
1727 * and a new buf is requested.
1728 */
1729 /* ARGSUSED */
1730 static int
1731 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1732 {
1733 arc_buf_hdr_t *hdr = vbuf;
1734
1735 bzero(hdr, HDR_FULL_SIZE);
1736 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1737 refcount_create(&hdr->b_l1hdr.b_refcnt);
1738 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1739 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1740 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1741
1742 return (0);
1743 }
1744
1745 /* ARGSUSED */
1746 static int
1747 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1748 {
1749 arc_buf_hdr_t *hdr = vbuf;
1750
1751 bzero(hdr, HDR_L2ONLY_SIZE);
1752 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1753
1754 return (0);
1755 }
1756
1757 /* ARGSUSED */
1758 static int
1759 buf_cons(void *vbuf, void *unused, int kmflag)
1760 {
1761 arc_buf_t *buf = vbuf;
1762
1763 bzero(buf, sizeof (arc_buf_t));
1764 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1765 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1766
1767 return (0);
1768 }
1769
1770 /*
1771 * Destructor callback - called when a cached buf is
1772 * no longer required.
1773 */
1774 /* ARGSUSED */
1775 static void
1776 hdr_full_dest(void *vbuf, void *unused)
1777 {
1778 arc_buf_hdr_t *hdr = vbuf;
1779
1780 ASSERT(HDR_EMPTY(hdr));
1781 cv_destroy(&hdr->b_l1hdr.b_cv);
1782 refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1783 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1784 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1785 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1786 }
1787
1788 /* ARGSUSED */
1789 static void
1790 hdr_l2only_dest(void *vbuf, void *unused)
1791 {
1792 arc_buf_hdr_t *hdr = vbuf;
1793
1794 ASSERT(HDR_EMPTY(hdr));
1795 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1796 }
1797
1798 /* ARGSUSED */
1799 static void
1800 buf_dest(void *vbuf, void *unused)
1801 {
1802 arc_buf_t *buf = vbuf;
1803
1804 mutex_destroy(&buf->b_evict_lock);
1805 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1806 }
1807
1808 /*
1809 * Reclaim callback -- invoked when memory is low.
1810 */
1811 /* ARGSUSED */
1812 static void
1813 hdr_recl(void *unused)
1814 {
1815 dprintf("hdr_recl called\n");
1816 /*
1817 * umem calls the reclaim func when we destroy the buf cache,
1818 * which is after we do arc_fini().
1819 */
1820 if (!arc_dead)
1821 cv_signal(&arc_reclaim_thread_cv);
1822 }
1823
1824 static void
1825 buf_init(void)
1826 {
1827 uint64_t *ct;
1828 uint64_t hsize = 1ULL << 12;
1829 int i, j;
1830
1831 /*
1832 * The hash table is big enough to fill all of physical memory
1833 * with an average block size of zfs_arc_average_blocksize (default 8K).
1834 * By default, the table will take up
1835 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1836 */
1837 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
1838 hsize <<= 1;
1839 retry:
1840 buf_hash_table.ht_mask = hsize - 1;
1841 buf_hash_table.ht_table =
1842 kmem_zalloc(hsize * sizeof (struct ht_table), KM_NOSLEEP);
1843 if (buf_hash_table.ht_table == NULL) {
1844 ASSERT(hsize > (1ULL << 8));
1845 hsize >>= 1;
1846 goto retry;
1847 }
1848
1849 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1850 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1851 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1852 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1853 NULL, NULL, 0);
1854 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1855 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1856
1857 for (i = 0; i < 256; i++)
1858 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1859 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1860
1861 for (i = 0; i < hsize; i++) {
1862 mutex_init(&buf_hash_table.ht_table[i].lock,
1863 NULL, MUTEX_DEFAULT, NULL);
1864 }
1865 }
1866
1867 /* wait until krrp releases the buffer */
1868 static inline void
1869 arc_wait_for_krrp(arc_buf_hdr_t *hdr)
1870 {
1871 while (HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_krrp != 0)
1872 cv_wait(&hdr->b_l1hdr.b_cv, HDR_LOCK(hdr));
1873 }
1874
1875 /*
1876 * This is the size that the buf occupies in memory. If the buf is compressed,
1877 * it will correspond to the compressed size. You should use this method of
1878 * getting the buf size unless you explicitly need the logical size.
1879 */
1880 int32_t
1881 arc_buf_size(arc_buf_t *buf)
1882 {
1883 return (ARC_BUF_COMPRESSED(buf) ?
1884 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
1885 }
1886
1887 int32_t
1888 arc_buf_lsize(arc_buf_t *buf)
1889 {
1890 return (HDR_GET_LSIZE(buf->b_hdr));
1891 }
1892
1893 enum zio_compress
1894 arc_get_compression(arc_buf_t *buf)
1895 {
1896 return (ARC_BUF_COMPRESSED(buf) ?
1897 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
1898 }
1899
1900 #define ARC_MINTIME (hz>>4) /* 62 ms */
1901
1902 static inline boolean_t
1903 arc_buf_is_shared(arc_buf_t *buf)
1904 {
1905 boolean_t shared = (buf->b_data != NULL &&
1906 buf->b_hdr->b_l1hdr.b_pabd != NULL &&
1907 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
1908 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
1909 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
1910 IMPLY(shared, ARC_BUF_SHARED(buf));
1911 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
1912
1913 /*
1914 * It would be nice to assert arc_can_share() too, but the "hdr isn't
1915 * already being shared" requirement prevents us from doing that.
1916 */
1917
1918 return (shared);
1919 }
1920
1921 /*
1922 * Free the checksum associated with this header. If there is no checksum, this
1923 * is a no-op.
1924 */
1925 static inline void
1926 arc_cksum_free(arc_buf_hdr_t *hdr)
1927 {
1928 ASSERT(HDR_HAS_L1HDR(hdr));
1929 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1930 if (hdr->b_freeze_cksum != NULL) {
1931 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1932 hdr->b_freeze_cksum = NULL;
1933 }
1934 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1935 }
1936
1937 /*
1938 * Return true iff at least one of the bufs on hdr is not compressed.
1939 */
1940 static boolean_t
1941 arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
1942 {
1943 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
1944 if (!ARC_BUF_COMPRESSED(b)) {
1945 return (B_TRUE);
1946 }
1947 }
1948 return (B_FALSE);
1949 }
1950
1951 /*
1952 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
1953 * matches the checksum that is stored in the hdr. If there is no checksum,
1954 * or if the buf is compressed, this is a no-op.
1955 */
1956 static void
1957 arc_cksum_verify(arc_buf_t *buf)
1958 {
1959 arc_buf_hdr_t *hdr = buf->b_hdr;
1960 zio_cksum_t zc;
1961
1962 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1963 return;
1964
1965 if (ARC_BUF_COMPRESSED(buf)) {
1966 ASSERT(hdr->b_freeze_cksum == NULL ||
1967 arc_hdr_has_uncompressed_buf(hdr));
1968 return;
1969 }
1970
1971 ASSERT(HDR_HAS_L1HDR(hdr));
1972
1973 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1974 if (hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
1975 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1976 return;
1977 }
1978
1979 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
1980 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_freeze_cksum, zc))
1981 panic("buffer modified while frozen!");
1982 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1983 }
1984
1985 static boolean_t
1986 arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
1987 {
1988 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp);
1989 boolean_t valid_cksum;
1990
1991 ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
1992 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
1993
1994 /*
1995 * We rely on the blkptr's checksum to determine if the block
1996 * is valid or not. When compressed arc is enabled, the l2arc
1997 * writes the block to the l2arc just as it appears in the pool.
1998 * This allows us to use the blkptr's checksum to validate the
1999 * data that we just read off of the l2arc without having to store
2000 * a separate checksum in the arc_buf_hdr_t. However, if compressed
2001 * arc is disabled, then the data written to the l2arc is always
2002 * uncompressed and won't match the block as it exists in the main
2003 * pool. When this is the case, we must first compress it if it is
2004 * compressed on the main pool before we can validate the checksum.
2005 */
2006 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) {
2007 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
2008 uint64_t lsize = HDR_GET_LSIZE(hdr);
2009 uint64_t csize;
2010
2011 void *cbuf = zio_buf_alloc(HDR_GET_PSIZE(hdr));
2012 csize = zio_compress_data(compress, zio->io_abd, cbuf, lsize);
2013 abd_t *cdata = abd_get_from_buf(cbuf, HDR_GET_PSIZE(hdr));
2014 abd_take_ownership_of_buf(cdata, B_TRUE);
2015
2016 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr));
2017 if (csize < HDR_GET_PSIZE(hdr)) {
2018 /*
2019 * Compressed blocks are always a multiple of the
2020 * smallest ashift in the pool. Ideally, we would
2021 * like to round up the csize to the next
2022 * spa_min_ashift but that value may have changed
2023 * since the block was last written. Instead,
2024 * we rely on the fact that the hdr's psize
2025 * was set to the psize of the block when it was
2026 * last written. We set the csize to that value
2027 * and zero out any part that should not contain
2028 * data.
2029 */
2030 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize);
2031 csize = HDR_GET_PSIZE(hdr);
2032 }
2033 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL);
2034 }
2035
2036 /*
2037 * Block pointers always store the checksum for the logical data.
2038 * If the block pointer has the gang bit set, then the checksum
2039 * it represents is for the reconstituted data and not for an
2040 * individual gang member. The zio pipeline, however, must be able to
2041 * determine the checksum of each of the gang constituents so it
2042 * treats the checksum comparison differently than what we need
2043 * for l2arc blocks. This prevents us from using the
2044 * zio_checksum_error() interface directly. Instead we must call the
2045 * zio_checksum_error_impl() so that we can ensure the checksum is
2046 * generated using the correct checksum algorithm and accounts for the
2047 * logical I/O size and not just a gang fragment.
2048 */
2049 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
2050 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
2051 zio->io_offset, NULL) == 0);
2052 zio_pop_transforms(zio);
2053 return (valid_cksum);
2054 }
2055
2056 /*
2057 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
2058 * checksum and attaches it to the buf's hdr so that we can ensure that the buf
2059 * isn't modified later on. If buf is compressed or there is already a checksum
2060 * on the hdr, this is a no-op (we only checksum uncompressed bufs).
2061 */
2062 static void
2063 arc_cksum_compute(arc_buf_t *buf)
2064 {
2065 arc_buf_hdr_t *hdr = buf->b_hdr;
2066
2067 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
2068 return;
2069
2070 ASSERT(HDR_HAS_L1HDR(hdr));
2071
2072 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
2073 if (hdr->b_freeze_cksum != NULL) {
2074 ASSERT(arc_hdr_has_uncompressed_buf(hdr));
2075 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
2076 return;
2077 } else if (ARC_BUF_COMPRESSED(buf)) {
2078 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
2079 return;
2080 }
2081
2082 ASSERT(!ARC_BUF_COMPRESSED(buf));
2083 hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
2084 KM_SLEEP);
2085 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
2086 hdr->b_freeze_cksum);
2087 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
2088 arc_buf_watch(buf);
2089 }
2090
2091 #ifndef _KERNEL
2092 typedef struct procctl {
2093 long cmd;
2094 prwatch_t prwatch;
2095 } procctl_t;
2096 #endif
2097
2098 /* ARGSUSED */
2099 static void
2100 arc_buf_unwatch(arc_buf_t *buf)
2101 {
2102 #ifndef _KERNEL
2103 if (arc_watch) {
2104 int result;
2105 procctl_t ctl;
2106 ctl.cmd = PCWATCH;
2107 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
2108 ctl.prwatch.pr_size = 0;
2109 ctl.prwatch.pr_wflags = 0;
2110 result = write(arc_procfd, &ctl, sizeof (ctl));
2111 ASSERT3U(result, ==, sizeof (ctl));
2112 }
2113 #endif
2114 }
2115
2116 /* ARGSUSED */
2117 static void
2118 arc_buf_watch(arc_buf_t *buf)
2119 {
2120 #ifndef _KERNEL
2121 if (arc_watch) {
2122 int result;
2123 procctl_t ctl;
2124 ctl.cmd = PCWATCH;
2125 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
2126 ctl.prwatch.pr_size = arc_buf_size(buf);
2127 ctl.prwatch.pr_wflags = WA_WRITE;
2128 result = write(arc_procfd, &ctl, sizeof (ctl));
2129 ASSERT3U(result, ==, sizeof (ctl));
2130 }
2131 #endif
2132 }
2133
2134 static arc_buf_contents_t
2135 arc_buf_type(arc_buf_hdr_t *hdr)
2136 {
2137 arc_buf_contents_t type;
2138
2139 if (HDR_ISTYPE_METADATA(hdr)) {
2140 type = ARC_BUFC_METADATA;
2141 } else if (HDR_ISTYPE_DDT(hdr)) {
2142 type = ARC_BUFC_DDT;
2143 } else {
2144 type = ARC_BUFC_DATA;
2145 }
2146 VERIFY3U(hdr->b_type, ==, type);
2147 return (type);
2148 }
2149
2150 boolean_t
2151 arc_is_metadata(arc_buf_t *buf)
2152 {
2153 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
2154 }
2155
2156 static uint32_t
2157 arc_bufc_to_flags(arc_buf_contents_t type)
2158 {
2159 switch (type) {
2160 case ARC_BUFC_DATA:
2161 /* metadata field is 0 if buffer contains normal data */
2162 return (0);
2163 case ARC_BUFC_METADATA:
2164 return (ARC_FLAG_BUFC_METADATA);
2165 case ARC_BUFC_DDT:
2166 return (ARC_FLAG_BUFC_DDT);
2167 default:
2168 break;
2169 }
2170 panic("undefined ARC buffer type!");
2171 return ((uint32_t)-1);
2172 }
2173
2174 static arc_buf_contents_t
2175 arc_flags_to_bufc(uint32_t flags)
2176 {
2177 if (flags & ARC_FLAG_BUFC_DDT)
2178 return (ARC_BUFC_DDT);
2179 if (flags & ARC_FLAG_BUFC_METADATA)
2180 return (ARC_BUFC_METADATA);
2181 return (ARC_BUFC_DATA);
2182 }
2183
2184 void
2185 arc_buf_thaw(arc_buf_t *buf)
2186 {
2187 arc_buf_hdr_t *hdr = buf->b_hdr;
2188
2189 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
2190 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2191
2192 arc_cksum_verify(buf);
2193
2194 /*
2195 * Compressed buffers do not manipulate the b_freeze_cksum or
2196 * allocate b_thawed.
2197 */
2198 if (ARC_BUF_COMPRESSED(buf)) {
2199 ASSERT(hdr->b_freeze_cksum == NULL ||
2200 arc_hdr_has_uncompressed_buf(hdr));
2201 return;
2202 }
2203
2204 ASSERT(HDR_HAS_L1HDR(hdr));
2205 arc_cksum_free(hdr);
2206
2207 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
2208 #ifdef ZFS_DEBUG
2209 if (zfs_flags & ZFS_DEBUG_MODIFY) {
2210 if (hdr->b_l1hdr.b_thawed != NULL)
2211 kmem_free(hdr->b_l1hdr.b_thawed, 1);
2212 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
2213 }
2214 #endif
2215
2216 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
2217
2218 arc_buf_unwatch(buf);
2219 }
2220
2221 void
2222 arc_buf_freeze(arc_buf_t *buf)
2223 {
2224 arc_buf_hdr_t *hdr = buf->b_hdr;
2225 kmutex_t *hash_lock;
2226
2227 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
2228 return;
2229
2230 if (ARC_BUF_COMPRESSED(buf)) {
2231 ASSERT(hdr->b_freeze_cksum == NULL ||
2232 arc_hdr_has_uncompressed_buf(hdr));
2233 return;
2234 }
2235
2236 hash_lock = HDR_LOCK(hdr);
2237 mutex_enter(hash_lock);
2238
2239 ASSERT(HDR_HAS_L1HDR(hdr));
2240 ASSERT(hdr->b_freeze_cksum != NULL ||
2241 hdr->b_l1hdr.b_state == arc_anon);
2242 arc_cksum_compute(buf);
2243 mutex_exit(hash_lock);
2244 }
2245
2246 /*
2247 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
2248 * the following functions should be used to ensure that the flags are
2249 * updated in a thread-safe way. When manipulating the flags either
2250 * the hash_lock must be held or the hdr must be undiscoverable. This
2251 * ensures that we're not racing with any other threads when updating
2252 * the flags.
2253 */
2254 static inline void
2255 arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
2256 {
2257 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2258 hdr->b_flags |= flags;
2259 }
2260
2261 static inline void
2262 arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
2263 {
2264 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2265 hdr->b_flags &= ~flags;
2266 }
2267
2268 /*
2269 * Setting the compression bits in the arc_buf_hdr_t's b_flags is
2270 * done in a special way since we have to clear and set bits
2271 * at the same time. Consumers that wish to set the compression bits
2272 * must use this function to ensure that the flags are updated in
2273 * thread-safe manner.
2274 */
2275 static void
2276 arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
2277 {
2278 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2279
2280 /*
2281 * Holes and embedded blocks will always have a psize = 0 so
2282 * we ignore the compression of the blkptr and set the
2283 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF.
2284 * Holes and embedded blocks remain anonymous so we don't
2285 * want to uncompress them. Mark them as uncompressed.
2286 */
2287 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
2288 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
2289 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
2290 ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
2291 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
2292 } else {
2293 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
2294 HDR_SET_COMPRESS(hdr, cmp);
2295 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
2296 ASSERT(HDR_COMPRESSION_ENABLED(hdr));
2297 }
2298 }
2299
2300 /*
2301 * Looks for another buf on the same hdr which has the data decompressed, copies
2302 * from it, and returns true. If no such buf exists, returns false.
2303 */
2304 static boolean_t
2305 arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
2306 {
2307 arc_buf_hdr_t *hdr = buf->b_hdr;
2308 boolean_t copied = B_FALSE;
2309
2310 ASSERT(HDR_HAS_L1HDR(hdr));
2311 ASSERT3P(buf->b_data, !=, NULL);
2312 ASSERT(!ARC_BUF_COMPRESSED(buf));
2313
2314 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
2315 from = from->b_next) {
2316 /* can't use our own data buffer */
2317 if (from == buf) {
2318 continue;
2319 }
2320
2321 if (!ARC_BUF_COMPRESSED(from)) {
2322 bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
2323 copied = B_TRUE;
2324 break;
2325 }
2326 }
2327
2328 /*
2329 * There were no decompressed bufs, so there should not be a
2330 * checksum on the hdr either.
2331 */
2332 EQUIV(!copied, hdr->b_freeze_cksum == NULL);
2333
2334 return (copied);
2335 }
2336
2337 /*
2338 * Given a buf that has a data buffer attached to it, this function will
2339 * efficiently fill the buf with data of the specified compression setting from
2340 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
2341 * are already sharing a data buf, no copy is performed.
2342 *
2343 * If the buf is marked as compressed but uncompressed data was requested, this
2344 * will allocate a new data buffer for the buf, remove that flag, and fill the
2345 * buf with uncompressed data. You can't request a compressed buf on a hdr with
2346 * uncompressed data, and (since we haven't added support for it yet) if you
2347 * want compressed data your buf must already be marked as compressed and have
2348 * the correct-sized data buffer.
2349 */
2350 static int
2351 arc_buf_fill(arc_buf_t *buf, boolean_t compressed)
2352 {
2353 arc_buf_hdr_t *hdr = buf->b_hdr;
2354 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
2355 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
2356
2357 ASSERT3P(buf->b_data, !=, NULL);
2358 IMPLY(compressed, hdr_compressed);
2359 IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
2360
2361 if (hdr_compressed == compressed) {
2362 if (!arc_buf_is_shared(buf)) {
2363 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
2364 arc_buf_size(buf));
2365 }
2366 } else {
2367 ASSERT(hdr_compressed);
2368 ASSERT(!compressed);
2369 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
2370
2371 /*
2372 * If the buf is sharing its data with the hdr, unlink it and
2373 * allocate a new data buffer for the buf.
2374 */
2375 if (arc_buf_is_shared(buf)) {
2376 ASSERT(ARC_BUF_COMPRESSED(buf));
2377
2378 /* We need to give the buf it's own b_data */
2379 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2380 buf->b_data =
2381 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2382 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2383
2384 /* Previously overhead was 0; just add new overhead */
2385 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
2386 } else if (ARC_BUF_COMPRESSED(buf)) {
2387 /* We need to reallocate the buf's b_data */
2388 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
2389 buf);
2390 buf->b_data =
2391 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2392
2393 /* We increased the size of b_data; update overhead */
2394 ARCSTAT_INCR(arcstat_overhead_size,
2395 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
2396 }
2397
2398 /*
2399 * Regardless of the buf's previous compression settings, it
2400 * should not be compressed at the end of this function.
2401 */
2402 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
2403
2404 /*
2405 * Try copying the data from another buf which already has a
2406 * decompressed version. If that's not possible, it's time to
2407 * bite the bullet and decompress the data from the hdr.
2408 */
2409 if (arc_buf_try_copy_decompressed_data(buf)) {
2410 /* Skip byteswapping and checksumming (already done) */
2411 ASSERT3P(hdr->b_freeze_cksum, !=, NULL);
2412 return (0);
2413 } else {
2414 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
2415 hdr->b_l1hdr.b_pabd, buf->b_data,
2416 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2417
2418 /*
2419 * Absent hardware errors or software bugs, this should
2420 * be impossible, but log it anyway so we can debug it.
2421 */
2422 if (error != 0) {
2423 zfs_dbgmsg(
2424 "hdr %p, compress %d, psize %d, lsize %d",
2425 hdr, HDR_GET_COMPRESS(hdr),
2426 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2427 return (SET_ERROR(EIO));
2428 }
2429 }
2430 }
2431
2432 /* Byteswap the buf's data if necessary */
2433 if (bswap != DMU_BSWAP_NUMFUNCS) {
2434 ASSERT(!HDR_SHARED_DATA(hdr));
2435 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
2436 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
2437 }
2438
2439 /* Compute the hdr's checksum if necessary */
2440 arc_cksum_compute(buf);
2441
2442 return (0);
2443 }
2444
2445 int
2446 arc_decompress(arc_buf_t *buf)
2447 {
2448 return (arc_buf_fill(buf, B_FALSE));
2449 }
2450
2451 /*
2452 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
2453 */
2454 static uint64_t
2455 arc_hdr_size(arc_buf_hdr_t *hdr)
2456 {
2457 uint64_t size;
2458
2459 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
2460 HDR_GET_PSIZE(hdr) > 0) {
2461 size = HDR_GET_PSIZE(hdr);
2462 } else {
2463 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
2464 size = HDR_GET_LSIZE(hdr);
2465 }
2466 return (size);
2467 }
2468
2469 /*
2470 * Increment the amount of evictable space in the arc_state_t's refcount.
2471 * We account for the space used by the hdr and the arc buf individually
2472 * so that we can add and remove them from the refcount individually.
2473 */
2474 static void
2475 arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
2476 {
2477 arc_buf_contents_t type = arc_buf_type(hdr);
2478
2479 ASSERT(HDR_HAS_L1HDR(hdr));
2480
2481 if (GHOST_STATE(state)) {
2482 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2483 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2484 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2485 (void) refcount_add_many(&state->arcs_esize[type],
2486 HDR_GET_LSIZE(hdr), hdr);
2487 return;
2488 }
2489
2490 ASSERT(!GHOST_STATE(state));
2491 if (hdr->b_l1hdr.b_pabd != NULL) {
2492 (void) refcount_add_many(&state->arcs_esize[type],
2493 arc_hdr_size(hdr), hdr);
2494 }
2495 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2496 buf = buf->b_next) {
2497 if (arc_buf_is_shared(buf))
2498 continue;
2499 (void) refcount_add_many(&state->arcs_esize[type],
2500 arc_buf_size(buf), buf);
2501 }
2502 }
2503
2504 /*
2505 * Decrement the amount of evictable space in the arc_state_t's refcount.
2506 * We account for the space used by the hdr and the arc buf individually
2507 * so that we can add and remove them from the refcount individually.
2508 */
2509 static void
2510 arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
2511 {
2512 arc_buf_contents_t type = arc_buf_type(hdr);
2513
2514 ASSERT(HDR_HAS_L1HDR(hdr));
2515
2516 if (GHOST_STATE(state)) {
2517 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2518 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2519 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2520 (void) refcount_remove_many(&state->arcs_esize[type],
2521 HDR_GET_LSIZE(hdr), hdr);
2522 return;
2523 }
2524
2525 ASSERT(!GHOST_STATE(state));
2526 if (hdr->b_l1hdr.b_pabd != NULL) {
2527 (void) refcount_remove_many(&state->arcs_esize[type],
2528 arc_hdr_size(hdr), hdr);
2529 }
2530 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2531 buf = buf->b_next) {
2532 if (arc_buf_is_shared(buf))
2533 continue;
2534 (void) refcount_remove_many(&state->arcs_esize[type],
2535 arc_buf_size(buf), buf);
2536 }
2537 }
2538
2539 /*
2540 * Add a reference to this hdr indicating that someone is actively
2541 * referencing that memory. When the refcount transitions from 0 to 1,
2542 * we remove it from the respective arc_state_t list to indicate that
2543 * it is not evictable.
2544 */
2545 static void
2546 add_reference(arc_buf_hdr_t *hdr, void *tag)
2547 {
2548 ASSERT(HDR_HAS_L1HDR(hdr));
2549 if (!MUTEX_HELD(HDR_LOCK(hdr))) {
2550 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
2551 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2552 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2553 }
2554
2555 arc_state_t *state = hdr->b_l1hdr.b_state;
2556
2557 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
2558 (state != arc_anon)) {
2559 /* We don't use the L2-only state list. */
2560 if (state != arc_l2c_only) {
2561 multilist_remove(state->arcs_list[arc_buf_type(hdr)],
2562 hdr);
2563 arc_evictable_space_decrement(hdr, state);
2564 }
2565 /* remove the prefetch flag if we get a reference */
2566 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
2567 }
2568 }
2569
2570 /*
2571 * Remove a reference from this hdr. When the reference transitions from
2572 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
2573 * list making it eligible for eviction.
2574 */
2575 static int
2576 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
2577 {
2578 int cnt;
2579 arc_state_t *state = hdr->b_l1hdr.b_state;
2580
2581 ASSERT(HDR_HAS_L1HDR(hdr));
2582 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
2583 ASSERT(!GHOST_STATE(state));
2584
2585 /*
2586 * arc_l2c_only counts as a ghost state so we don't need to explicitly
2587 * check to prevent usage of the arc_l2c_only list.
2588 */
2589 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
2590 (state != arc_anon)) {
2591 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
2592 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
2593 arc_evictable_space_increment(hdr, state);
2594 }
2595 return (cnt);
2596 }
2597
2598 /*
2599 * Move the supplied buffer to the indicated state. The hash lock
2600 * for the buffer must be held by the caller.
2601 */
2602 static void
2603 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
2604 kmutex_t *hash_lock)
2605 {
2606 arc_state_t *old_state;
2607 int64_t refcnt;
2608 uint32_t bufcnt;
2609 boolean_t update_old, update_new;
2610 arc_buf_contents_t buftype = arc_buf_type(hdr);
2611
2612 /*
2613 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
2614 * in arc_read() when bringing a buffer out of the L2ARC. However, the
2615 * L1 hdr doesn't always exist when we change state to arc_anon before
2616 * destroying a header, in which case reallocating to add the L1 hdr is
2617 * pointless.
2618 */
2619 if (HDR_HAS_L1HDR(hdr)) {
2620 old_state = hdr->b_l1hdr.b_state;
2621 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
2622 bufcnt = hdr->b_l1hdr.b_bufcnt;
2623 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL);
2624 } else {
2625 old_state = arc_l2c_only;
2626 refcnt = 0;
2627 bufcnt = 0;
2628 update_old = B_FALSE;
2629 }
2630 update_new = update_old;
2631
2632 ASSERT(MUTEX_HELD(hash_lock));
2633 ASSERT3P(new_state, !=, old_state);
2634 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
2635 ASSERT(old_state != arc_anon || bufcnt <= 1);
2636
2637 /*
2638 * If this buffer is evictable, transfer it from the
2639 * old state list to the new state list.
2640 */
2641 if (refcnt == 0) {
2642 if (old_state != arc_anon && old_state != arc_l2c_only) {
2643 ASSERT(HDR_HAS_L1HDR(hdr));
2644 multilist_remove(old_state->arcs_list[buftype], hdr);
2645
2646 if (GHOST_STATE(old_state)) {
2647 ASSERT0(bufcnt);
2648 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2649 update_old = B_TRUE;
2650 }
2651 arc_evictable_space_decrement(hdr, old_state);
2652 }
2653 if (new_state != arc_anon && new_state != arc_l2c_only) {
2654
2655 /*
2656 * An L1 header always exists here, since if we're
2657 * moving to some L1-cached state (i.e. not l2c_only or
2658 * anonymous), we realloc the header to add an L1hdr
2659 * beforehand.
2660 */
2661 ASSERT(HDR_HAS_L1HDR(hdr));
2662 multilist_insert(new_state->arcs_list[buftype], hdr);
2663
2664 if (GHOST_STATE(new_state)) {
2665 ASSERT0(bufcnt);
2666 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2667 update_new = B_TRUE;
2668 }
2669 arc_evictable_space_increment(hdr, new_state);
2670 }
2671 }
2672
2673 ASSERT(!HDR_EMPTY(hdr));
2674 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) {
2675 arc_wait_for_krrp(hdr);
2676 buf_hash_remove(hdr);
2677 }
2678
2679 /* adjust state sizes (ignore arc_l2c_only) */
2680
2681 if (update_new && new_state != arc_l2c_only) {
2682 ASSERT(HDR_HAS_L1HDR(hdr));
2683 if (GHOST_STATE(new_state)) {
2684 ASSERT0(bufcnt);
2685
2686 /*
2687 * When moving a header to a ghost state, we first
2688 * remove all arc buffers. Thus, we'll have a
2689 * bufcnt of zero, and no arc buffer to use for
2690 * the reference. As a result, we use the arc
2691 * header pointer for the reference.
2692 */
2693 (void) refcount_add_many(&new_state->arcs_size,
2694 HDR_GET_LSIZE(hdr), hdr);
2695 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2696 } else {
2697 uint32_t buffers = 0;
2698
2699 /*
2700 * Each individual buffer holds a unique reference,
2701 * thus we must remove each of these references one
2702 * at a time.
2703 */
2704 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2705 buf = buf->b_next) {
2706 ASSERT3U(bufcnt, !=, 0);
2707 buffers++;
2708
2709 /*
2710 * When the arc_buf_t is sharing the data
2711 * block with the hdr, the owner of the
2712 * reference belongs to the hdr. Only
2713 * add to the refcount if the arc_buf_t is
2714 * not shared.
2715 */
2716 if (arc_buf_is_shared(buf))
2717 continue;
2718
2719 (void) refcount_add_many(&new_state->arcs_size,
2720 arc_buf_size(buf), buf);
2721 }
2722 ASSERT3U(bufcnt, ==, buffers);
2723
2724 if (hdr->b_l1hdr.b_pabd != NULL) {
2725 (void) refcount_add_many(&new_state->arcs_size,
2726 arc_hdr_size(hdr), hdr);
2727 } else {
2728 ASSERT(GHOST_STATE(old_state));
2729 }
2730 }
2731 }
2732
2733 if (update_old && old_state != arc_l2c_only) {
2734 ASSERT(HDR_HAS_L1HDR(hdr));
2735 if (GHOST_STATE(old_state)) {
2736 ASSERT0(bufcnt);
2737 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2738
2739 /*
2740 * When moving a header off of a ghost state,
2741 * the header will not contain any arc buffers.
2742 * We use the arc header pointer for the reference
2743 * which is exactly what we did when we put the
2744 * header on the ghost state.
2745 */
2746
2747 (void) refcount_remove_many(&old_state->arcs_size,
2748 HDR_GET_LSIZE(hdr), hdr);
2749 } else {
2750 uint32_t buffers = 0;
2751
2752 /*
2753 * Each individual buffer holds a unique reference,
2754 * thus we must remove each of these references one
2755 * at a time.
2756 */
2757 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2758 buf = buf->b_next) {
2759 ASSERT3U(bufcnt, !=, 0);
2760 buffers++;
2761
2762 /*
2763 * When the arc_buf_t is sharing the data
2764 * block with the hdr, the owner of the
2765 * reference belongs to the hdr. Only
2766 * add to the refcount if the arc_buf_t is
2767 * not shared.
2768 */
2769 if (arc_buf_is_shared(buf))
2770 continue;
2771
2772 (void) refcount_remove_many(
2773 &old_state->arcs_size, arc_buf_size(buf),
2774 buf);
2775 }
2776 ASSERT3U(bufcnt, ==, buffers);
2777 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2778 (void) refcount_remove_many(
2779 &old_state->arcs_size, arc_hdr_size(hdr), hdr);
2780 }
2781 }
2782
2783 if (HDR_HAS_L1HDR(hdr))
2784 hdr->b_l1hdr.b_state = new_state;
2785
2786 /*
2787 * L2 headers should never be on the L2 state list since they don't
2788 * have L1 headers allocated.
2789 */
2790 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]));
2791 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
2792 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DDT]));
2793 }
2794
2795 void
2796 arc_space_consume(uint64_t space, arc_space_type_t type)
2797 {
2798 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2799
2800 switch (type) {
2801 case ARC_SPACE_DATA:
2802 ARCSTAT_INCR(arcstat_data_size, space);
2803 break;
2804 case ARC_SPACE_META:
2805 ARCSTAT_INCR(arcstat_metadata_size, space);
2806 break;
2807 case ARC_SPACE_DDT:
2808 ARCSTAT_INCR(arcstat_ddt_size, space);
2809 break;
2810 case ARC_SPACE_OTHER:
2811 ARCSTAT_INCR(arcstat_other_size, space);
2812 break;
2813 case ARC_SPACE_HDRS:
2814 ARCSTAT_INCR(arcstat_hdr_size, space);
2815 break;
2816 case ARC_SPACE_L2HDRS:
2817 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
2818 break;
2819 }
2820
2821 if (type != ARC_SPACE_DATA && type != ARC_SPACE_DDT)
2822 ARCSTAT_INCR(arcstat_meta_used, space);
2823
2824 atomic_add_64(&arc_size, space);
2825 }
2826
2827 void
2828 arc_space_return(uint64_t space, arc_space_type_t type)
2829 {
2830 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2831
2832 switch (type) {
2833 case ARC_SPACE_DATA:
2834 ARCSTAT_INCR(arcstat_data_size, -space);
2835 break;
2836 case ARC_SPACE_META:
2837 ARCSTAT_INCR(arcstat_metadata_size, -space);
2838 break;
2839 case ARC_SPACE_DDT:
2840 ARCSTAT_INCR(arcstat_ddt_size, -space);
2841 break;
2842 case ARC_SPACE_OTHER:
2843 ARCSTAT_INCR(arcstat_other_size, -space);
2844 break;
2845 case ARC_SPACE_HDRS:
2846 ARCSTAT_INCR(arcstat_hdr_size, -space);
2847 break;
2848 case ARC_SPACE_L2HDRS:
2849 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
2850 break;
2851 }
2852
2853 if (type != ARC_SPACE_DATA && type != ARC_SPACE_DDT) {
2854 ASSERT(arc_meta_used >= space);
2855 if (arc_meta_max < arc_meta_used)
2856 arc_meta_max = arc_meta_used;
2857 ARCSTAT_INCR(arcstat_meta_used, -space);
2858 }
2859
2860 ASSERT(arc_size >= space);
2861 atomic_add_64(&arc_size, -space);
2862 }
2863
2864 /*
2865 * Given a hdr and a buf, returns whether that buf can share its b_data buffer
2866 * with the hdr's b_pabd.
2867 */
2868 static boolean_t
2869 arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2870 {
2871 /*
2872 * The criteria for sharing a hdr's data are:
2873 * 1. the hdr's compression matches the buf's compression
2874 * 2. the hdr doesn't need to be byteswapped
2875 * 3. the hdr isn't already being shared
2876 * 4. the buf is either compressed or it is the last buf in the hdr list
2877 *
2878 * Criterion #4 maintains the invariant that shared uncompressed
2879 * bufs must be the final buf in the hdr's b_buf list. Reading this, you
2880 * might ask, "if a compressed buf is allocated first, won't that be the
2881 * last thing in the list?", but in that case it's impossible to create
2882 * a shared uncompressed buf anyway (because the hdr must be compressed
2883 * to have the compressed buf). You might also think that #3 is
2884 * sufficient to make this guarantee, however it's possible
2885 * (specifically in the rare L2ARC write race mentioned in
2886 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that
2887 * is sharable, but wasn't at the time of its allocation. Rather than
2888 * allow a new shared uncompressed buf to be created and then shuffle
2889 * the list around to make it the last element, this simply disallows
2890 * sharing if the new buf isn't the first to be added.
2891 */
2892 ASSERT3P(buf->b_hdr, ==, hdr);
2893 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF;
2894 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
2895 return (buf_compressed == hdr_compressed &&
2896 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
2897 !HDR_SHARED_DATA(hdr) &&
2898 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
2899 }
2900
2901 /*
2902 * Allocate a buf for this hdr. If you care about the data that's in the hdr,
2903 * or if you want a compressed buffer, pass those flags in. Returns 0 if the
2904 * copy was made successfully, or an error code otherwise.
2905 */
2906 static int
2907 arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed,
2908 boolean_t fill, arc_buf_t **ret)
2909 {
2910 arc_buf_t *buf;
2911
2912 ASSERT(HDR_HAS_L1HDR(hdr));
2913 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2914 VERIFY(hdr->b_type == ARC_BUFC_DATA ||
2915 hdr->b_type == ARC_BUFC_METADATA ||
2916 hdr->b_type == ARC_BUFC_DDT);
2917 ASSERT3P(ret, !=, NULL);
2918 ASSERT3P(*ret, ==, NULL);
2919
2920 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2921 buf->b_hdr = hdr;
2922 buf->b_data = NULL;
2923 buf->b_next = hdr->b_l1hdr.b_buf;
2924 buf->b_flags = 0;
2925
2926 add_reference(hdr, tag);
2927
2928 /*
2929 * We're about to change the hdr's b_flags. We must either
2930 * hold the hash_lock or be undiscoverable.
2931 */
2932 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2933
2934 /*
2935 * Only honor requests for compressed bufs if the hdr is actually
2936 * compressed.
2937 */
2938 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF)
2939 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2940
2941 /*
2942 * If the hdr's data can be shared then we share the data buffer and
2943 * set the appropriate bit in the hdr's b_flags to indicate the hdr is
2944 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new
2945 * buffer to store the buf's data.
2946 *
2947 * There are two additional restrictions here because we're sharing
2948 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
2949 * actively involved in an L2ARC write, because if this buf is used by
2950 * an arc_write() then the hdr's data buffer will be released when the
2951 * write completes, even though the L2ARC write might still be using it.
2952 * Second, the hdr's ABD must be linear so that the buf's user doesn't
2953 * need to be ABD-aware.
2954 */
2955 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) &&
2956 abd_is_linear(hdr->b_l1hdr.b_pabd);
2957
2958 /* Set up b_data and sharing */
2959 if (can_share) {
2960 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
2961 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2962 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2963 } else {
2964 buf->b_data =
2965 arc_get_data_buf(hdr, arc_buf_size(buf), buf);
2966 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2967 }
2968 VERIFY3P(buf->b_data, !=, NULL);
2969
2970 hdr->b_l1hdr.b_buf = buf;
2971 hdr->b_l1hdr.b_bufcnt += 1;
2972
2973 /*
2974 * If the user wants the data from the hdr, we need to either copy or
2975 * decompress the data.
2976 */
2977 if (fill) {
2978 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0));
2979 }
2980
2981 return (0);
2982 }
2983
2984 static char *arc_onloan_tag = "onloan";
2985
2986 static inline void
2987 arc_loaned_bytes_update(int64_t delta)
2988 {
2989 atomic_add_64(&arc_loaned_bytes, delta);
2990
2991 /* assert that it did not wrap around */
2992 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
2993 }
2994
2995 /*
2996 * Allocates an ARC buf header that's in an evicted & L2-cached state.
2997 * This is used during l2arc reconstruction to make empty ARC buffers
2998 * which circumvent the regular disk->arc->l2arc path and instead come
2999 * into being in the reverse order, i.e. l2arc->arc.
3000 */
3001 static arc_buf_hdr_t *
3002 arc_buf_alloc_l2only(uint64_t load_guid, arc_buf_contents_t type,
3003 l2arc_dev_t *dev, dva_t dva, uint64_t daddr, uint64_t lsize,
3004 uint64_t psize, uint64_t birth, zio_cksum_t cksum, int checksum_type,
3005 enum zio_compress compress, boolean_t arc_compress)
3006 {
3007 arc_buf_hdr_t *hdr;
3008
3009 if (type == ARC_BUFC_DDT && !zfs_arc_segregate_ddt)
3010 type = ARC_BUFC_METADATA;
3011
3012 ASSERT(lsize != 0);
3013 hdr = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
3014 ASSERT(HDR_EMPTY(hdr));
3015 ASSERT3P(hdr->b_freeze_cksum, ==, NULL);
3016
3017 hdr->b_spa = load_guid;
3018 hdr->b_type = type;
3019 hdr->b_flags = 0;
3020
3021 if (arc_compress)
3022 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
3023 else
3024 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
3025
3026 HDR_SET_COMPRESS(hdr, compress);
3027
3028 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L2HDR);
3029 hdr->b_dva = dva;
3030 hdr->b_birth = birth;
3031 if (checksum_type != ZIO_CHECKSUM_OFF) {
3032 hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
3033 bcopy(&cksum, hdr->b_freeze_cksum, sizeof (cksum));
3034 }
3035
3036 HDR_SET_PSIZE(hdr, psize);
3037 HDR_SET_LSIZE(hdr, lsize);
3038
3039 hdr->b_l2hdr.b_dev = dev;
3040 hdr->b_l2hdr.b_daddr = daddr;
3041
3042 return (hdr);
3043 }
3044
3045 /*
3046 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
3047 * flight data by arc_tempreserve_space() until they are "returned". Loaned
3048 * buffers must be returned to the arc before they can be used by the DMU or
3049 * freed.
3050 */
3051 arc_buf_t *
3052 arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
3053 {
3054 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
3055 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
3056
3057 arc_loaned_bytes_update(size);
3058
3059 return (buf);
3060 }
3061
3062 arc_buf_t *
3063 arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
3064 enum zio_compress compression_type)
3065 {
3066 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
3067 psize, lsize, compression_type);
3068
3069 arc_loaned_bytes_update(psize);
3070
3071 return (buf);
3072 }
3073
3074
3075 /*
3076 * Return a loaned arc buffer to the arc.
3077 */
3078 void
3079 arc_return_buf(arc_buf_t *buf, void *tag)
3080 {
3081 arc_buf_hdr_t *hdr = buf->b_hdr;
3082
3083 ASSERT3P(buf->b_data, !=, NULL);
3084 ASSERT(HDR_HAS_L1HDR(hdr));
3085 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
3086 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
3087
3088 arc_loaned_bytes_update(-arc_buf_size(buf));
3089 }
3090
3091 /* Detach an arc_buf from a dbuf (tag) */
3092 void
3093 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
3094 {
3095 arc_buf_hdr_t *hdr = buf->b_hdr;
3096
3097 ASSERT3P(buf->b_data, !=, NULL);
3098 ASSERT(HDR_HAS_L1HDR(hdr));
3099 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
3100 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
3101
3102 arc_loaned_bytes_update(arc_buf_size(buf));
3103 }
3104
3105 static void
3106 l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
3107 {
3108 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
3109
3110 df->l2df_abd = abd;
3111 df->l2df_size = size;
3112 df->l2df_type = type;
3113 mutex_enter(&l2arc_free_on_write_mtx);
3114 list_insert_head(l2arc_free_on_write, df);
3115 mutex_exit(&l2arc_free_on_write_mtx);
3116 }
3117
3118 static void
3119 arc_hdr_free_on_write(arc_buf_hdr_t *hdr)
3120 {
3121 arc_state_t *state = hdr->b_l1hdr.b_state;
3122 arc_buf_contents_t type = arc_buf_type(hdr);
3123 uint64_t size = arc_hdr_size(hdr);
3124
3125 /* protected by hash lock, if in the hash table */
3126 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
3127 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3128 ASSERT(state != arc_anon && state != arc_l2c_only);
3129
3130 (void) refcount_remove_many(&state->arcs_esize[type],
3131 size, hdr);
3132 }
3133 (void) refcount_remove_many(&state->arcs_size, size, hdr);
3134 if (type == ARC_BUFC_DDT) {
3135 arc_space_return(size, ARC_SPACE_DDT);
3136 } else if (type == ARC_BUFC_METADATA) {
3137 arc_space_return(size, ARC_SPACE_META);
3138 } else {
3139 ASSERT(type == ARC_BUFC_DATA);
3140 arc_space_return(size, ARC_SPACE_DATA);
3141 }
3142
3143 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
3144 }
3145
3146 /*
3147 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the
3148 * data buffer, we transfer the refcount ownership to the hdr and update
3149 * the appropriate kstats.
3150 */
3151 static void
3152 arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3153 {
3154 arc_state_t *state = hdr->b_l1hdr.b_state;
3155
3156 ASSERT(arc_can_share(hdr, buf));
3157 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3158 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3159
3160 /*
3161 * Start sharing the data buffer. We transfer the
3162 * refcount ownership to the hdr since it always owns
3163 * the refcount whenever an arc_buf_t is shared.
3164 */
3165 refcount_transfer_ownership(&state->arcs_size, buf, hdr);
3166 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
3167 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
3168 !HDR_ISTYPE_DATA(hdr));
3169 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
3170 buf->b_flags |= ARC_BUF_FLAG_SHARED;
3171
3172 /*
3173 * Since we've transferred ownership to the hdr we need
3174 * to increment its compressed and uncompressed kstats and
3175 * decrement the overhead size.
3176 */
3177 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
3178 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3179 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
3180 }
3181
3182 static void
3183 arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3184 {
3185 arc_state_t *state = hdr->b_l1hdr.b_state;
3186
3187 ASSERT(arc_buf_is_shared(buf));
3188 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3189 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3190
3191 /*
3192 * We are no longer sharing this buffer so we need
3193 * to transfer its ownership to the rightful owner.
3194 */
3195 refcount_transfer_ownership(&state->arcs_size, hdr, buf);
3196 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
3197 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
3198 abd_put(hdr->b_l1hdr.b_pabd);
3199 hdr->b_l1hdr.b_pabd = NULL;
3200 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
3201
3202 /*
3203 * Since the buffer is no longer shared between
3204 * the arc buf and the hdr, count it as overhead.
3205 */
3206 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
3207 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3208 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
3209 }
3210
3211 /*
3212 * Remove an arc_buf_t from the hdr's buf list and return the last
3213 * arc_buf_t on the list. If no buffers remain on the list then return
3214 * NULL.
3215 */
3216 static arc_buf_t *
3217 arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3218 {
3219 ASSERT(HDR_HAS_L1HDR(hdr));
3220 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3221
3222 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
3223 arc_buf_t *lastbuf = NULL;
3224
3225 /*
3226 * Remove the buf from the hdr list and locate the last
3227 * remaining buffer on the list.
3228 */
3229 while (*bufp != NULL) {
3230 if (*bufp == buf)
3231 *bufp = buf->b_next;
3232
3233 /*
3234 * If we've removed a buffer in the middle of
3235 * the list then update the lastbuf and update
3236 * bufp.
3237 */
3238 if (*bufp != NULL) {
3239 lastbuf = *bufp;
3240 bufp = &(*bufp)->b_next;
3241 }
3242 }
3243 buf->b_next = NULL;
3244 ASSERT3P(lastbuf, !=, buf);
3245 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
3246 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
3247 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
3248
3249 return (lastbuf);
3250 }
3251
3252 /*
3253 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
3254 * list and free it.
3255 */
3256 static void
3257 arc_buf_destroy_impl(arc_buf_t *buf)
3258 {
3259 arc_buf_hdr_t *hdr = buf->b_hdr;
3260
3261 /*
3262 * Free up the data associated with the buf but only if we're not
3263 * sharing this with the hdr. If we are sharing it with the hdr, the
3264 * hdr is responsible for doing the free.
3265 */
3266 if (buf->b_data != NULL) {
3267 /*
3268 * We're about to change the hdr's b_flags. We must either
3269 * hold the hash_lock or be undiscoverable.
3270 */
3271 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3272
3273 arc_cksum_verify(buf);
3274 arc_buf_unwatch(buf);
3275
3276 if (arc_buf_is_shared(buf)) {
3277 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
3278 } else {
3279 uint64_t size = arc_buf_size(buf);
3280 arc_free_data_buf(hdr, buf->b_data, size, buf);
3281 ARCSTAT_INCR(arcstat_overhead_size, -size);
3282 }
3283 buf->b_data = NULL;
3284
3285 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3286 hdr->b_l1hdr.b_bufcnt -= 1;
3287 }
3288
3289 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
3290
3291 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
3292 /*
3293 * If the current arc_buf_t is sharing its data buffer with the
3294 * hdr, then reassign the hdr's b_pabd to share it with the new
3295 * buffer at the end of the list. The shared buffer is always
3296 * the last one on the hdr's buffer list.
3297 *
3298 * There is an equivalent case for compressed bufs, but since
3299 * they aren't guaranteed to be the last buf in the list and
3300 * that is an exceedingly rare case, we just allow that space be
3301 * wasted temporarily.
3302 */
3303 if (lastbuf != NULL) {
3304 /* Only one buf can be shared at once */
3305 VERIFY(!arc_buf_is_shared(lastbuf));
3306 /* hdr is uncompressed so can't have compressed buf */
3307 VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
3308
3309 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3310 arc_hdr_free_pabd(hdr);
3311
3312 /*
3313 * We must setup a new shared block between the
3314 * last buffer and the hdr. The data would have
3315 * been allocated by the arc buf so we need to transfer
3316 * ownership to the hdr since it's now being shared.
3317 */
3318 arc_share_buf(hdr, lastbuf);
3319 }
3320 } else if (HDR_SHARED_DATA(hdr)) {
3321 /*
3322 * Uncompressed shared buffers are always at the end
3323 * of the list. Compressed buffers don't have the
3324 * same requirements. This makes it hard to
3325 * simply assert that the lastbuf is shared so
3326 * we rely on the hdr's compression flags to determine
3327 * if we have a compressed, shared buffer.
3328 */
3329 ASSERT3P(lastbuf, !=, NULL);
3330 ASSERT(arc_buf_is_shared(lastbuf) ||
3331 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
3332 }
3333
3334 /*
3335 * Free the checksum if we're removing the last uncompressed buf from
3336 * this hdr.
3337 */
3338 if (!arc_hdr_has_uncompressed_buf(hdr)) {
3339 arc_cksum_free(hdr);
3340 }
3341
3342 /* clean up the buf */
3343 buf->b_hdr = NULL;
3344 kmem_cache_free(buf_cache, buf);
3345 }
3346
3347 static void
3348 arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr)
3349 {
3350 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
3351 ASSERT(HDR_HAS_L1HDR(hdr));
3352 ASSERT(!HDR_SHARED_DATA(hdr));
3353
3354 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3355 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr);
3356 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3357 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3358
3359 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
3360 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3361 arc_update_hit_stat(hdr, B_TRUE);
3362 }
3363
3364 static void
3365 arc_hdr_free_pabd(arc_buf_hdr_t *hdr)
3366 {
3367 ASSERT(HDR_HAS_L1HDR(hdr));
3368 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3369
3370 /*
3371 * If the hdr is currently being written to the l2arc then
3372 * we defer freeing the data by adding it to the l2arc_free_on_write
3373 * list. The l2arc will free the data once it's finished
3374 * writing it to the l2arc device.
3375 */
3376 if (HDR_L2_WRITING(hdr)) {
3377 arc_hdr_free_on_write(hdr);
3378 ARCSTAT_BUMP(arcstat_l2_free_on_write);
3379 } else {
3380 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
3381 arc_hdr_size(hdr), hdr);
3382 }
3383 hdr->b_l1hdr.b_pabd = NULL;
3384 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3385
3386 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
3387 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3388 }
3389
3390 static arc_buf_hdr_t *
3391 arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
3392 enum zio_compress compression_type, arc_buf_contents_t type)
3393 {
3394 arc_buf_hdr_t *hdr;
3395
3396 ASSERT3U(lsize, >, 0);
3397
3398 if (type == ARC_BUFC_DDT && !zfs_arc_segregate_ddt)
3399 type = ARC_BUFC_METADATA;
3400 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA ||
3401 type == ARC_BUFC_DDT);
3402
3403 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
3404 ASSERT(HDR_EMPTY(hdr));
3405 ASSERT3P(hdr->b_freeze_cksum, ==, NULL);
3406 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL);
3407 HDR_SET_PSIZE(hdr, psize);
3408 HDR_SET_LSIZE(hdr, lsize);
3409 hdr->b_spa = spa;
3410 hdr->b_type = type;
3411 hdr->b_flags = 0;
3412 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
3413 arc_hdr_set_compress(hdr, compression_type);
3414
3415 hdr->b_l1hdr.b_state = arc_anon;
3416 hdr->b_l1hdr.b_arc_access = 0;
3417 hdr->b_l1hdr.b_bufcnt = 0;
3418 hdr->b_l1hdr.b_buf = NULL;
3419
3420 /*
3421 * Allocate the hdr's buffer. This will contain either
3422 * the compressed or uncompressed data depending on the block
3423 * it references and compressed arc enablement.
3424 */
3425 arc_hdr_alloc_pabd(hdr);
3426 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3427
3428 return (hdr);
3429 }
3430
3431 /*
3432 * Transition between the two allocation states for the arc_buf_hdr struct.
3433 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
3434 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
3435 * version is used when a cache buffer is only in the L2ARC in order to reduce
3436 * memory usage.
3437 */
3438 static arc_buf_hdr_t *
3439 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
3440 {
3441 ASSERT(HDR_HAS_L2HDR(hdr));
3442
3443 arc_buf_hdr_t *nhdr;
3444 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3445
3446 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
3447 (old == hdr_l2only_cache && new == hdr_full_cache));
3448
3449 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
3450
3451 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
3452 buf_hash_remove(hdr);
3453
3454 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
3455
3456 if (new == hdr_full_cache) {
3457 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3458 /*
3459 * arc_access and arc_change_state need to be aware that a
3460 * header has just come out of L2ARC, so we set its state to
3461 * l2c_only even though it's about to change.
3462 */
3463 nhdr->b_l1hdr.b_state = arc_l2c_only;
3464
3465 /* Verify previous threads set to NULL before freeing */
3466 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
3467 } else {
3468 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3469 ASSERT0(hdr->b_l1hdr.b_bufcnt);
3470 ASSERT3P(hdr->b_freeze_cksum, ==, NULL);
3471
3472 /*
3473 * If we've reached here, We must have been called from
3474 * arc_evict_hdr(), as such we should have already been
3475 * removed from any ghost list we were previously on
3476 * (which protects us from racing with arc_evict_state),
3477 * thus no locking is needed during this check.
3478 */
3479 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3480
3481 /*
3482 * A buffer must not be moved into the arc_l2c_only
3483 * state if it's not finished being written out to the
3484 * l2arc device. Otherwise, the b_l1hdr.b_pabd field
3485 * might try to be accessed, even though it was removed.
3486 */
3487 VERIFY(!HDR_L2_WRITING(hdr));
3488 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3489
3490 #ifdef ZFS_DEBUG
3491 if (hdr->b_l1hdr.b_thawed != NULL) {
3492 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3493 hdr->b_l1hdr.b_thawed = NULL;
3494 }
3495 #endif
3496
3497 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3498 }
3499 /*
3500 * The header has been reallocated so we need to re-insert it into any
3501 * lists it was on.
3502 */
3503 (void) buf_hash_insert(nhdr, NULL);
3504
3505 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
3506
3507 mutex_enter(&dev->l2ad_mtx);
3508
3509 /*
3510 * We must place the realloc'ed header back into the list at
3511 * the same spot. Otherwise, if it's placed earlier in the list,
3512 * l2arc_write_buffers() could find it during the function's
3513 * write phase, and try to write it out to the l2arc.
3514 */
3515 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
3516 list_remove(&dev->l2ad_buflist, hdr);
3517
3518 mutex_exit(&dev->l2ad_mtx);
3519
3520 /*
3521 * Since we're using the pointer address as the tag when
3522 * incrementing and decrementing the l2ad_alloc refcount, we
3523 * must remove the old pointer (that we're about to destroy) and
3524 * add the new pointer to the refcount. Otherwise we'd remove
3525 * the wrong pointer address when calling arc_hdr_destroy() later.
3526 */
3527
3528 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
3529 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr);
3530
3531 buf_discard_identity(hdr);
3532 kmem_cache_free(old, hdr);
3533
3534 return (nhdr);
3535 }
3536
3537 /*
3538 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
3539 * The buf is returned thawed since we expect the consumer to modify it.
3540 */
3541 arc_buf_t *
3542 arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
3543 {
3544 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
3545 ZIO_COMPRESS_OFF, type);
3546 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3547
3548 arc_buf_t *buf = NULL;
3549 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf));
3550 arc_buf_thaw(buf);
3551
3552 return (buf);
3553 }
3554
3555 /*
3556 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
3557 * for bufs containing metadata.
3558 */
3559 arc_buf_t *
3560 arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
3561 enum zio_compress compression_type)
3562 {
3563 ASSERT3U(lsize, >, 0);
3564 ASSERT3U(lsize, >=, psize);
3565 ASSERT(compression_type > ZIO_COMPRESS_OFF);
3566 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS);
3567
3568 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
3569 compression_type, ARC_BUFC_DATA);
3570 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3571
3572 arc_buf_t *buf = NULL;
3573 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf));
3574 arc_buf_thaw(buf);
3575 ASSERT3P(hdr->b_freeze_cksum, ==, NULL);
3576
3577 if (!arc_buf_is_shared(buf)) {
3578 /*
3579 * To ensure that the hdr has the correct data in it if we call
3580 * arc_decompress() on this buf before it's been written to
3581 * disk, it's easiest if we just set up sharing between the
3582 * buf and the hdr.
3583 */
3584 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd));
3585 arc_hdr_free_pabd(hdr);
3586 arc_share_buf(hdr, buf);
3587 }
3588
3589 return (buf);
3590 }
3591
3592 static void
3593 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
3594 {
3595 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3596 l2arc_dev_t *dev = l2hdr->b_dev;
3597 uint64_t psize = arc_hdr_size(hdr);
3598
3599 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
3600 ASSERT(HDR_HAS_L2HDR(hdr));
3601
3602 list_remove(&dev->l2ad_buflist, hdr);
3603
3604 ARCSTAT_INCR(arcstat_l2_psize, -psize);
3605 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
3606
3607 /*
3608 * l2ad_vdev can be NULL here if we async evicted it
3609 */
3610 if (dev->l2ad_vdev != NULL)
3611 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0);
3612
3613 (void) refcount_remove_many(&dev->l2ad_alloc, psize, hdr);
3614 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
3615 }
3616
3617 static void
3618 arc_hdr_destroy(arc_buf_hdr_t *hdr)
3619 {
3620 if (HDR_HAS_L1HDR(hdr)) {
3621 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
3622 hdr->b_l1hdr.b_bufcnt > 0);
3623 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3624 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3625 }
3626 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3627 ASSERT(!HDR_IN_HASH_TABLE(hdr));
3628
3629 if (HDR_HAS_L2HDR(hdr)) {
3630 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3631 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
3632
3633 /* To avoid racing with L2ARC the header needs to be locked */
3634 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
3635
3636 if (!buflist_held)
3637 mutex_enter(&dev->l2ad_mtx);
3638
3639 /*
3640 * L2ARC buflist has been held, so we can safety discard
3641 * identity, otherwise L2ARC can lock incorrect mutex
3642 * for the hdr, that will cause a panic. That is possible,
3643 * because a mutex is selected according to identity.
3644 */
3645 if (!HDR_EMPTY(hdr))
3646 buf_discard_identity(hdr);
3647
3648 /*
3649 * Even though we checked this conditional above, we
3650 * need to check this again now that we have the
3651 * l2ad_mtx. This is because we could be racing with
3652 * another thread calling l2arc_evict() which might have
3653 * destroyed this header's L2 portion as we were waiting
3654 * to acquire the l2ad_mtx. If that happens, we don't
3655 * want to re-destroy the header's L2 portion.
3656 */
3657 if (HDR_HAS_L2HDR(hdr))
3658 arc_hdr_l2hdr_destroy(hdr);
3659
3660 if (!buflist_held)
3661 mutex_exit(&dev->l2ad_mtx);
3662 }
3663
3664 if (!HDR_EMPTY(hdr))
3665 buf_discard_identity(hdr);
3666
3667 if (HDR_HAS_L1HDR(hdr)) {
3668 arc_cksum_free(hdr);
3669
3670 while (hdr->b_l1hdr.b_buf != NULL)
3671 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
3672
3673 #ifdef ZFS_DEBUG
3674 if (hdr->b_l1hdr.b_thawed != NULL) {
3675 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3676 hdr->b_l1hdr.b_thawed = NULL;
3677 }
3678 #endif
3679
3680 if (hdr->b_l1hdr.b_pabd != NULL) {
3681 arc_hdr_free_pabd(hdr);
3682 }
3683 }
3684
3685 ASSERT3P(hdr->b_hash_next, ==, NULL);
3686 if (HDR_HAS_L1HDR(hdr)) {
3687 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3688 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
3689 kmem_cache_free(hdr_full_cache, hdr);
3690 } else {
3691 kmem_cache_free(hdr_l2only_cache, hdr);
3692 }
3693 }
3694
3695 void
3696 arc_buf_destroy(arc_buf_t *buf, void* tag)
3697 {
3698 arc_buf_hdr_t *hdr = buf->b_hdr;
3699 kmutex_t *hash_lock = HDR_LOCK(hdr);
3700
3701 if (hdr->b_l1hdr.b_state == arc_anon) {
3702 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
3703 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3704 VERIFY0(remove_reference(hdr, NULL, tag));
3705 arc_hdr_destroy(hdr);
3706 return;
3707 }
3708
3709 mutex_enter(hash_lock);
3710 ASSERT3P(hdr, ==, buf->b_hdr);
3711 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3712 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3713 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
3714 ASSERT3P(buf->b_data, !=, NULL);
3715
3716 (void) remove_reference(hdr, hash_lock, tag);
3717 arc_buf_destroy_impl(buf);
3718 mutex_exit(hash_lock);
3719 }
3720
3721 /*
3722 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
3723 * state of the header is dependent on it's state prior to entering this
3724 * function. The following transitions are possible:
3725 *
3726 * - arc_mru -> arc_mru_ghost
3727 * - arc_mfu -> arc_mfu_ghost
3728 * - arc_mru_ghost -> arc_l2c_only
3729 * - arc_mru_ghost -> deleted
3730 * - arc_mfu_ghost -> arc_l2c_only
3731 * - arc_mfu_ghost -> deleted
3732 */
3733 static int64_t
3734 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3735 {
3736 arc_state_t *evicted_state, *state;
3737 int64_t bytes_evicted = 0;
3738
3739 ASSERT(MUTEX_HELD(hash_lock));
3740 ASSERT(HDR_HAS_L1HDR(hdr));
3741
3742 arc_wait_for_krrp(hdr);
3743
3744 state = hdr->b_l1hdr.b_state;
3745 if (GHOST_STATE(state)) {
3746 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3747 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3748
3749 /*
3750 * l2arc_write_buffers() relies on a header's L1 portion
3751 * (i.e. its b_pabd field) during it's write phase.
3752 * Thus, we cannot push a header onto the arc_l2c_only
3753 * state (removing it's L1 piece) until the header is
3754 * done being written to the l2arc.
3755 */
3756 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
3757 ARCSTAT_BUMP(arcstat_evict_l2_skip);
3758 return (bytes_evicted);
3759 }
3760
3761 ARCSTAT_BUMP(arcstat_deleted);
3762 bytes_evicted += HDR_GET_LSIZE(hdr);
3763
3764 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
3765
3766 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3767 if (HDR_HAS_L2HDR(hdr)) {
3768 /*
3769 * This buffer is cached on the 2nd Level ARC;
3770 * don't destroy the header.
3771 */
3772 arc_change_state(arc_l2c_only, hdr, hash_lock);
3773 /*
3774 * dropping from L1+L2 cached to L2-only,
3775 * realloc to remove the L1 header.
3776 */
3777 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
3778 hdr_l2only_cache);
3779 } else {
3780 arc_change_state(arc_anon, hdr, hash_lock);
3781 arc_hdr_destroy(hdr);
3782 }
3783 return (bytes_evicted);
3784 }
3785
3786 ASSERT(state == arc_mru || state == arc_mfu);
3787 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3788
3789 /* prefetch buffers have a minimum lifespan */
3790 if (HDR_IO_IN_PROGRESS(hdr) ||
3791 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
3792 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
3793 arc_min_prefetch_lifespan)) {
3794 ARCSTAT_BUMP(arcstat_evict_skip);
3795 return (bytes_evicted);
3796 }
3797
3798 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
3799 while (hdr->b_l1hdr.b_buf) {
3800 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
3801 if (!mutex_tryenter(&buf->b_evict_lock)) {
3802 ARCSTAT_BUMP(arcstat_mutex_miss);
3803 break;
3804 }
3805 if (buf->b_data != NULL)
3806 bytes_evicted += HDR_GET_LSIZE(hdr);
3807 mutex_exit(&buf->b_evict_lock);
3808 arc_buf_destroy_impl(buf);
3809 }
3810
3811 if (HDR_HAS_L2HDR(hdr)) {
3812 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
3813 } else {
3814 if (l2arc_write_eligible(hdr->b_spa, hdr)) {
3815 ARCSTAT_INCR(arcstat_evict_l2_eligible,
3816 HDR_GET_LSIZE(hdr));
3817 } else {
3818 ARCSTAT_INCR(arcstat_evict_l2_ineligible,
3819 HDR_GET_LSIZE(hdr));
3820 }
3821 }
3822
3823 if (hdr->b_l1hdr.b_bufcnt == 0) {
3824 arc_cksum_free(hdr);
3825
3826 bytes_evicted += arc_hdr_size(hdr);
3827
3828 /*
3829 * If this hdr is being evicted and has a compressed
3830 * buffer then we discard it here before we change states.
3831 * This ensures that the accounting is updated correctly
3832 * in arc_free_data_impl().
3833 */
3834 arc_hdr_free_pabd(hdr);
3835
3836 arc_change_state(evicted_state, hdr, hash_lock);
3837 ASSERT(HDR_IN_HASH_TABLE(hdr));
3838 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
3839 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
3840 }
3841
3842 return (bytes_evicted);
3843 }
3844
3845 static uint64_t
3846 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
3847 uint64_t spa, int64_t bytes)
3848 {
3849 multilist_sublist_t *mls;
3850 uint64_t bytes_evicted = 0;
3851 arc_buf_hdr_t *hdr;
3852 kmutex_t *hash_lock;
3853 int evict_count = 0;
3854
3855 ASSERT3P(marker, !=, NULL);
3856 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3857
3858 mls = multilist_sublist_lock(ml, idx);
3859
3860 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
3861 hdr = multilist_sublist_prev(mls, marker)) {
3862 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
3863 (evict_count >= zfs_arc_evict_batch_limit))
3864 break;
3865
3866 /*
3867 * To keep our iteration location, move the marker
3868 * forward. Since we're not holding hdr's hash lock, we
3869 * must be very careful and not remove 'hdr' from the
3870 * sublist. Otherwise, other consumers might mistake the
3871 * 'hdr' as not being on a sublist when they call the
3872 * multilist_link_active() function (they all rely on
3873 * the hash lock protecting concurrent insertions and
3874 * removals). multilist_sublist_move_forward() was
3875 * specifically implemented to ensure this is the case
3876 * (only 'marker' will be removed and re-inserted).
3877 */
3878 multilist_sublist_move_forward(mls, marker);
3879
3880 /*
3881 * The only case where the b_spa field should ever be
3882 * zero, is the marker headers inserted by
3883 * arc_evict_state(). It's possible for multiple threads
3884 * to be calling arc_evict_state() concurrently (e.g.
3885 * dsl_pool_close() and zio_inject_fault()), so we must
3886 * skip any markers we see from these other threads.
3887 */
3888 if (hdr->b_spa == 0)
3889 continue;
3890
3891 /* we're only interested in evicting buffers of a certain spa */
3892 if (spa != 0 && hdr->b_spa != spa) {
3893 ARCSTAT_BUMP(arcstat_evict_skip);
3894 continue;
3895 }
3896
3897 hash_lock = HDR_LOCK(hdr);
3898
3899 /*
3900 * We aren't calling this function from any code path
3901 * that would already be holding a hash lock, so we're
3902 * asserting on this assumption to be defensive in case
3903 * this ever changes. Without this check, it would be
3904 * possible to incorrectly increment arcstat_mutex_miss
3905 * below (e.g. if the code changed such that we called
3906 * this function with a hash lock held).
3907 */
3908 ASSERT(!MUTEX_HELD(hash_lock));
3909
3910 if (mutex_tryenter(hash_lock)) {
3911 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
3912 mutex_exit(hash_lock);
3913
3914 bytes_evicted += evicted;
3915
3916 /*
3917 * If evicted is zero, arc_evict_hdr() must have
3918 * decided to skip this header, don't increment
3919 * evict_count in this case.
3920 */
3921 if (evicted != 0)
3922 evict_count++;
3923
3924 /*
3925 * If arc_size isn't overflowing, signal any
3926 * threads that might happen to be waiting.
3927 *
3928 * For each header evicted, we wake up a single
3929 * thread. If we used cv_broadcast, we could
3930 * wake up "too many" threads causing arc_size
3931 * to significantly overflow arc_c; since
3932 * arc_get_data_impl() doesn't check for overflow
3933 * when it's woken up (it doesn't because it's
3934 * possible for the ARC to be overflowing while
3935 * full of un-evictable buffers, and the
3936 * function should proceed in this case).
3937 *
3938 * If threads are left sleeping, due to not
3939 * using cv_broadcast, they will be woken up
3940 * just before arc_reclaim_thread() sleeps.
3941 */
3942 mutex_enter(&arc_reclaim_lock);
3943 if (!arc_is_overflowing())
3944 cv_signal(&arc_reclaim_waiters_cv);
3945 mutex_exit(&arc_reclaim_lock);
3946 } else {
3947 ARCSTAT_BUMP(arcstat_mutex_miss);
3948 }
3949 }
3950
3951 multilist_sublist_unlock(mls);
3952
3953 return (bytes_evicted);
3954 }
3955
3956 /*
3957 * Evict buffers from the given arc state, until we've removed the
3958 * specified number of bytes. Move the removed buffers to the
3959 * appropriate evict state.
3960 *
3961 * This function makes a "best effort". It skips over any buffers
3962 * it can't get a hash_lock on, and so, may not catch all candidates.
3963 * It may also return without evicting as much space as requested.
3964 *
3965 * If bytes is specified using the special value ARC_EVICT_ALL, this
3966 * will evict all available (i.e. unlocked and evictable) buffers from
3967 * the given arc state; which is used by arc_flush().
3968 */
3969 static uint64_t
3970 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
3971 arc_buf_contents_t type)
3972 {
3973 uint64_t total_evicted = 0;
3974 multilist_t *ml = state->arcs_list[type];
3975 int num_sublists;
3976 arc_buf_hdr_t **markers;
3977
3978 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3979
3980 num_sublists = multilist_get_num_sublists(ml);
3981
3982 /*
3983 * If we've tried to evict from each sublist, made some
3984 * progress, but still have not hit the target number of bytes
3985 * to evict, we want to keep trying. The markers allow us to
3986 * pick up where we left off for each individual sublist, rather
3987 * than starting from the tail each time.
3988 */
3989 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
3990 for (int i = 0; i < num_sublists; i++) {
3991 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
3992
3993 /*
3994 * A b_spa of 0 is used to indicate that this header is
3995 * a marker. This fact is used in arc_adjust_type() and
3996 * arc_evict_state_impl().
3997 */
3998 markers[i]->b_spa = 0;
3999
4000 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
4001 multilist_sublist_insert_tail(mls, markers[i]);
4002 multilist_sublist_unlock(mls);
4003 }
4004
4005 /*
4006 * While we haven't hit our target number of bytes to evict, or
4007 * we're evicting all available buffers.
4008 */
4009 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
4010 /*
4011 * Start eviction using a randomly selected sublist,
4012 * this is to try and evenly balance eviction across all
4013 * sublists. Always starting at the same sublist
4014 * (e.g. index 0) would cause evictions to favor certain
4015 * sublists over others.
4016 */
4017 int sublist_idx = multilist_get_random_index(ml);
4018 uint64_t scan_evicted = 0;
4019
4020 for (int i = 0; i < num_sublists; i++) {
4021 uint64_t bytes_remaining;
4022 uint64_t bytes_evicted;
4023
4024 if (bytes == ARC_EVICT_ALL)
4025 bytes_remaining = ARC_EVICT_ALL;
4026 else if (total_evicted < bytes)
4027 bytes_remaining = bytes - total_evicted;
4028 else
4029 break;
4030
4031 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
4032 markers[sublist_idx], spa, bytes_remaining);
4033
4034 scan_evicted += bytes_evicted;
4035 total_evicted += bytes_evicted;
4036
4037 /* we've reached the end, wrap to the beginning */
4038 if (++sublist_idx >= num_sublists)
4039 sublist_idx = 0;
4040 }
4041
4042 /*
4043 * If we didn't evict anything during this scan, we have
4044 * no reason to believe we'll evict more during another
4045 * scan, so break the loop.
4046 */
4047 if (scan_evicted == 0) {
4048 /* This isn't possible, let's make that obvious */
4049 ASSERT3S(bytes, !=, 0);
4050
4051 /*
4052 * When bytes is ARC_EVICT_ALL, the only way to
4053 * break the loop is when scan_evicted is zero.
4054 * In that case, we actually have evicted enough,
4055 * so we don't want to increment the kstat.
4056 */
4057 if (bytes != ARC_EVICT_ALL) {
4058 ASSERT3S(total_evicted, <, bytes);
4059 ARCSTAT_BUMP(arcstat_evict_not_enough);
4060 }
4061
4062 break;
4063 }
4064 }
4065
4066 for (int i = 0; i < num_sublists; i++) {
4067 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
4068 multilist_sublist_remove(mls, markers[i]);
4069 multilist_sublist_unlock(mls);
4070
4071 kmem_cache_free(hdr_full_cache, markers[i]);
4072 }
4073 kmem_free(markers, sizeof (*markers) * num_sublists);
4074
4075 return (total_evicted);
4076 }
4077
4078 /*
4079 * Flush all "evictable" data of the given type from the arc state
4080 * specified. This will not evict any "active" buffers (i.e. referenced).
4081 *
4082 * When 'retry' is set to B_FALSE, the function will make a single pass
4083 * over the state and evict any buffers that it can. Since it doesn't
4084 * continually retry the eviction, it might end up leaving some buffers
4085 * in the ARC due to lock misses.
4086 *
4087 * When 'retry' is set to B_TRUE, the function will continually retry the
4088 * eviction until *all* evictable buffers have been removed from the
4089 * state. As a result, if concurrent insertions into the state are
4090 * allowed (e.g. if the ARC isn't shutting down), this function might
4091 * wind up in an infinite loop, continually trying to evict buffers.
4092 */
4093 static uint64_t
4094 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
4095 boolean_t retry)
4096 {
4097 uint64_t evicted = 0;
4098
4099 while (refcount_count(&state->arcs_esize[type]) != 0) {
4100 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
4101
4102 if (!retry)
4103 break;
4104 }
4105
4106 return (evicted);
4107 }
4108
4109 /*
4110 * Evict the specified number of bytes from the state specified,
4111 * restricting eviction to the spa and type given. This function
4112 * prevents us from trying to evict more from a state's list than
4113 * is "evictable", and to skip evicting altogether when passed a
4114 * negative value for "bytes". In contrast, arc_evict_state() will
4115 * evict everything it can, when passed a negative value for "bytes".
4116 */
4117 static uint64_t
4118 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
4119 arc_buf_contents_t type)
4120 {
4121 int64_t delta;
4122
4123 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) {
4124 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes);
4125 return (arc_evict_state(state, spa, delta, type));
4126 }
4127
4128 return (0);
4129 }
4130
4131 /*
4132 * Depending on the value of adjust_ddt arg evict either DDT (B_TRUE)
4133 * or metadata (B_TRUE) buffers.
4134 * Evict metadata or DDT buffers from the cache, such that arc_meta_used or
4135 * arc_ddt_size is capped by the arc_meta_limit or arc_ddt_limit tunable.
4136 */
4137 static uint64_t
4138 arc_adjust_meta_or_ddt(boolean_t adjust_ddt)
4139 {
4140 uint64_t total_evicted = 0;
4141 int64_t target, over_limit;
4142 arc_buf_contents_t type;
4143
4144 if (adjust_ddt) {
4145 over_limit = arc_ddt_size - arc_ddt_limit;
4146 type = ARC_BUFC_DDT;
4147 } else {
4148 over_limit = arc_meta_used - arc_meta_limit;
4149 type = ARC_BUFC_METADATA;
4150 }
4151
4152 /*
4153 * If we're over the limit, we want to evict enough
4154 * to get back under the limit. We don't want to
4155 * evict so much that we drop the MRU below arc_p, though. If
4156 * we're over the meta limit more than we're over arc_p, we
4157 * evict some from the MRU here, and some from the MFU below.
4158 */
4159 target = MIN(over_limit,
4160 (int64_t)(refcount_count(&arc_anon->arcs_size) +
4161 refcount_count(&arc_mru->arcs_size) - arc_p));
4162
4163 total_evicted += arc_adjust_impl(arc_mru, 0, target, type);
4164
4165 over_limit = adjust_ddt ? arc_ddt_size - arc_ddt_limit :
4166 arc_meta_used - arc_meta_limit;
4167
4168 /*
4169 * Similar to the above, we want to evict enough bytes to get us
4170 * below the meta limit, but not so much as to drop us below the
4171 * space allotted to the MFU (which is defined as arc_c - arc_p).
4172 */
4173 target = MIN(over_limit,
4174 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p)));
4175
4176 total_evicted += arc_adjust_impl(arc_mfu, 0, target, type);
4177
4178 return (total_evicted);
4179 }
4180
4181 /*
4182 * Return the type of the oldest buffer in the given arc state
4183 *
4184 * This function will select a random sublists of type ARC_BUFC_DATA,
4185 * ARC_BUFC_METADATA, and ARC_BUFC_DDT. The tail of each sublist
4186 * is compared, and the type which contains the "older" buffer will be
4187 * returned.
4188 */
4189 static arc_buf_contents_t
4190 arc_adjust_type(arc_state_t *state)
4191 {
4192 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
4193 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
4194 multilist_t *ddt_ml = state->arcs_list[ARC_BUFC_DDT];
4195 int data_idx = multilist_get_random_index(data_ml);
4196 int meta_idx = multilist_get_random_index(meta_ml);
4197 int ddt_idx = multilist_get_random_index(ddt_ml);
4198 multilist_sublist_t *data_mls;
4199 multilist_sublist_t *meta_mls;
4200 multilist_sublist_t *ddt_mls;
4201 arc_buf_contents_t type = ARC_BUFC_DATA; /* silence compiler warning */
4202 arc_buf_hdr_t *data_hdr;
4203 arc_buf_hdr_t *meta_hdr;
4204 arc_buf_hdr_t *ddt_hdr;
4205 clock_t oldest;
4206
4207 /*
4208 * We keep the sublist lock until we're finished, to prevent
4209 * the headers from being destroyed via arc_evict_state().
4210 */
4211 data_mls = multilist_sublist_lock(data_ml, data_idx);
4212 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
4213 ddt_mls = multilist_sublist_lock(ddt_ml, ddt_idx);
4214
4215 /*
4216 * These two loops are to ensure we skip any markers that
4217 * might be at the tail of the lists due to arc_evict_state().
4218 */
4219
4220 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
4221 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
4222 if (data_hdr->b_spa != 0)
4223 break;
4224 }
4225
4226 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
4227 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
4228 if (meta_hdr->b_spa != 0)
4229 break;
4230 }
4231
4232 for (ddt_hdr = multilist_sublist_tail(ddt_mls); ddt_hdr != NULL;
4233 ddt_hdr = multilist_sublist_prev(ddt_mls, ddt_hdr)) {
4234 if (ddt_hdr->b_spa != 0)
4235 break;
4236 }
4237
4238 if (data_hdr == NULL && meta_hdr == NULL && ddt_hdr == NULL) {
4239 type = ARC_BUFC_DATA;
4240 } else if (data_hdr != NULL && meta_hdr != NULL && ddt_hdr != NULL) {
4241 /* The headers can't be on the sublist without an L1 header */
4242 ASSERT(HDR_HAS_L1HDR(data_hdr));
4243 ASSERT(HDR_HAS_L1HDR(meta_hdr));
4244 ASSERT(HDR_HAS_L1HDR(ddt_hdr));
4245
4246 oldest = data_hdr->b_l1hdr.b_arc_access;
4247 type = ARC_BUFC_DATA;
4248 if (oldest > meta_hdr->b_l1hdr.b_arc_access) {
4249 oldest = meta_hdr->b_l1hdr.b_arc_access;
4250 type = ARC_BUFC_METADATA;
4251 }
4252 if (oldest > ddt_hdr->b_l1hdr.b_arc_access) {
4253 type = ARC_BUFC_DDT;
4254 }
4255 } else if (data_hdr == NULL && ddt_hdr == NULL) {
4256 ASSERT3P(meta_hdr, !=, NULL);
4257 type = ARC_BUFC_METADATA;
4258 } else if (meta_hdr == NULL && ddt_hdr == NULL) {
4259 ASSERT3P(data_hdr, !=, NULL);
4260 type = ARC_BUFC_DATA;
4261 } else if (meta_hdr == NULL && data_hdr == NULL) {
4262 ASSERT3P(ddt_hdr, !=, NULL);
4263 type = ARC_BUFC_DDT;
4264 } else if (data_hdr != NULL && ddt_hdr != NULL) {
4265 ASSERT3P(meta_hdr, ==, NULL);
4266
4267 /* The headers can't be on the sublist without an L1 header */
4268 ASSERT(HDR_HAS_L1HDR(data_hdr));
4269 ASSERT(HDR_HAS_L1HDR(ddt_hdr));
4270
4271 if (data_hdr->b_l1hdr.b_arc_access <
4272 ddt_hdr->b_l1hdr.b_arc_access) {
4273 type = ARC_BUFC_DATA;
4274 } else {
4275 type = ARC_BUFC_DDT;
4276 }
4277 } else if (meta_hdr != NULL && ddt_hdr != NULL) {
4278 ASSERT3P(data_hdr, ==, NULL);
4279
4280 /* The headers can't be on the sublist without an L1 header */
4281 ASSERT(HDR_HAS_L1HDR(meta_hdr));
4282 ASSERT(HDR_HAS_L1HDR(ddt_hdr));
4283
4284 if (meta_hdr->b_l1hdr.b_arc_access <
4285 ddt_hdr->b_l1hdr.b_arc_access) {
4286 type = ARC_BUFC_METADATA;
4287 } else {
4288 type = ARC_BUFC_DDT;
4289 }
4290 } else if (meta_hdr != NULL && data_hdr != NULL) {
4291 ASSERT3P(ddt_hdr, ==, NULL);
4292
4293 /* The headers can't be on the sublist without an L1 header */
4294 ASSERT(HDR_HAS_L1HDR(data_hdr));
4295 ASSERT(HDR_HAS_L1HDR(meta_hdr));
4296
4297 if (data_hdr->b_l1hdr.b_arc_access <
4298 meta_hdr->b_l1hdr.b_arc_access) {
4299 type = ARC_BUFC_DATA;
4300 } else {
4301 type = ARC_BUFC_METADATA;
4302 }
4303 } else {
4304 /* should never get here */
4305 ASSERT(0);
4306 }
4307
4308 multilist_sublist_unlock(ddt_mls);
4309 multilist_sublist_unlock(meta_mls);
4310 multilist_sublist_unlock(data_mls);
4311
4312 return (type);
4313 }
4314
4315 /*
4316 * Evict buffers from the cache, such that arc_size is capped by arc_c.
4317 */
4318 static uint64_t
4319 arc_adjust(void)
4320 {
4321 uint64_t total_evicted = 0;
4322 uint64_t bytes;
4323 int64_t target;
4324
4325 /*
4326 * If we're over arc_meta_limit, we want to correct that before
4327 * potentially evicting data buffers below.
4328 */
4329 total_evicted += arc_adjust_meta_or_ddt(B_FALSE);
4330
4331 /*
4332 * If we're over arc_ddt_limit, we want to correct that before
4333 * potentially evicting data buffers below.
4334 */
4335 total_evicted += arc_adjust_meta_or_ddt(B_TRUE);
4336
4337 /*
4338 * Adjust MRU size
4339 *
4340 * If we're over the target cache size, we want to evict enough
4341 * from the list to get back to our target size. We don't want
4342 * to evict too much from the MRU, such that it drops below
4343 * arc_p. So, if we're over our target cache size more than
4344 * the MRU is over arc_p, we'll evict enough to get back to
4345 * arc_p here, and then evict more from the MFU below.
4346 */
4347 target = MIN((int64_t)(arc_size - arc_c),
4348 (int64_t)(refcount_count(&arc_anon->arcs_size) +
4349 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p));
4350
4351 /*
4352 * If we're below arc_meta_min, always prefer to evict data.
4353 * Otherwise, try to satisfy the requested number of bytes to
4354 * evict from the type which contains older buffers; in an
4355 * effort to keep newer buffers in the cache regardless of their
4356 * type. If we cannot satisfy the number of bytes from this
4357 * type, spill over into the next type.
4358 */
4359 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
4360 arc_meta_used > arc_meta_min) {
4361 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4362 total_evicted += bytes;
4363
4364 /*
4365 * If we couldn't evict our target number of bytes from
4366 * metadata, we try to get the rest from data.
4367 */
4368 target -= bytes;
4369
4370 bytes += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4371 total_evicted += bytes;
4372 } else {
4373 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4374 total_evicted += bytes;
4375
4376 /*
4377 * If we couldn't evict our target number of bytes from
4378 * data, we try to get the rest from metadata.
4379 */
4380 target -= bytes;
4381
4382 bytes += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4383 total_evicted += bytes;
4384 }
4385
4386 /*
4387 * If we couldn't evict our target number of bytes from
4388 * data and metadata, we try to get the rest from ddt.
4389 */
4390 target -= bytes;
4391 total_evicted +=
4392 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DDT);
4393
4394 /*
4395 * Adjust MFU size
4396 *
4397 * Now that we've tried to evict enough from the MRU to get its
4398 * size back to arc_p, if we're still above the target cache
4399 * size, we evict the rest from the MFU.
4400 */
4401 target = arc_size - arc_c;
4402
4403 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
4404 arc_meta_used > arc_meta_min) {
4405 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4406 total_evicted += bytes;
4407
4408 /*
4409 * If we couldn't evict our target number of bytes from
4410 * metadata, we try to get the rest from data.
4411 */
4412 target -= bytes;
4413
4414 bytes += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4415 total_evicted += bytes;
4416 } else {
4417 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4418 total_evicted += bytes;
4419
4420 /*
4421 * If we couldn't evict our target number of bytes from
4422 * data, we try to get the rest from data.
4423 */
4424 target -= bytes;
4425
4426 bytes += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4427 total_evicted += bytes;
4428 }
4429
4430 /*
4431 * If we couldn't evict our target number of bytes from
4432 * data and metadata, we try to get the rest from ddt.
4433 */
4434 target -= bytes;
4435 total_evicted +=
4436 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DDT);
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 = refcount_count(&arc_mru->arcs_size) +
4450 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 bytes += arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
4458 total_evicted += bytes;
4459
4460 target -= bytes;
4461
4462 total_evicted +=
4463 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DDT);
4464
4465 /*
4466 * We assume the sum of the mru list and mfu list is less than
4467 * or equal to arc_c (we enforced this above), which means we
4468 * can use the simpler of the two equations below:
4469 *
4470 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
4471 * mru ghost + mfu ghost <= arc_c
4472 */
4473 target = refcount_count(&arc_mru_ghost->arcs_size) +
4474 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
4475
4476 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
4477 total_evicted += bytes;
4478
4479 target -= bytes;
4480
4481 bytes += arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
4482 total_evicted += bytes;
4483
4484 target -= bytes;
4485
4486 total_evicted +=
4487 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DDT);
4488
4489 return (total_evicted);
4490 }
4491
4492 typedef struct arc_async_flush_data {
4493 uint64_t aaf_guid;
4494 boolean_t aaf_retry;
4495 } arc_async_flush_data_t;
4496
4497 static taskq_t *arc_flush_taskq;
4498
4499 static void
4500 arc_flush_impl(uint64_t guid, boolean_t retry)
4501 {
4502 arc_buf_contents_t arcs;
4503
4504 for (arcs = ARC_BUFC_DATA; arcs < ARC_BUFC_NUMTYPES; ++arcs) {
4505 (void) arc_flush_state(arc_mru, guid, arcs, retry);
4506 (void) arc_flush_state(arc_mfu, guid, arcs, retry);
4507 (void) arc_flush_state(arc_mru_ghost, guid, arcs, retry);
4508 (void) arc_flush_state(arc_mfu_ghost, guid, arcs, retry);
4509 }
4510 }
4511
4512 static void
4513 arc_flush_task(void *arg)
4514 {
4515 arc_async_flush_data_t *aaf = (arc_async_flush_data_t *)arg;
4516 arc_flush_impl(aaf->aaf_guid, aaf->aaf_retry);
4517 kmem_free(aaf, sizeof (arc_async_flush_data_t));
4518 }
4519
4520 boolean_t zfs_fastflush = B_TRUE;
4521
4522 void
4523 arc_flush(spa_t *spa, boolean_t retry)
4524 {
4525 uint64_t guid = 0;
4526 boolean_t async_flush = (spa != NULL ? zfs_fastflush : FALSE);
4527 arc_async_flush_data_t *aaf = NULL;
4528
4529 /*
4530 * If retry is B_TRUE, a spa must not be specified since we have
4531 * no good way to determine if all of a spa's buffers have been
4532 * evicted from an arc state.
4533 */
4534 ASSERT(!retry || spa == NULL);
4535
4536 if (spa != NULL) {
4537 guid = spa_load_guid(spa);
4538 if (async_flush) {
4539 aaf = kmem_alloc(sizeof (arc_async_flush_data_t),
4540 KM_SLEEP);
4541 aaf->aaf_guid = guid;
4542 aaf->aaf_retry = retry;
4543 }
4544 }
4545
4546 /*
4547 * Try to flush per-spa remaining ARC ghost buffers asynchronously
4548 * while a pool is being closed.
4549 * An ARC buffer is bound to spa only by guid, so buffer can
4550 * exist even when pool has already gone. If asynchronous flushing
4551 * fails we fall back to regular (synchronous) one.
4552 * NOTE: If asynchronous flushing had not yet finished when the pool
4553 * was imported again it wouldn't be a problem, even when guids before
4554 * and after export/import are the same. We can evict only unreferenced
4555 * buffers, other are skipped.
4556 */
4557 if (!async_flush || (taskq_dispatch(arc_flush_taskq, arc_flush_task,
4558 aaf, TQ_NOSLEEP) == NULL)) {
4559 arc_flush_impl(guid, retry);
4560 if (async_flush)
4561 kmem_free(aaf, sizeof (arc_async_flush_data_t));
4562 }
4563 }
4564
4565 void
4566 arc_shrink(int64_t to_free)
4567 {
4568 if (arc_c > arc_c_min) {
4569
4570 if (arc_c > arc_c_min + to_free)
4571 atomic_add_64(&arc_c, -to_free);
4572 else
4573 arc_c = arc_c_min;
4574
4575 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
4576 if (arc_c > arc_size)
4577 arc_c = MAX(arc_size, arc_c_min);
4578 if (arc_p > arc_c)
4579 arc_p = (arc_c >> 1);
4580 ASSERT(arc_c >= arc_c_min);
4581 ASSERT((int64_t)arc_p >= 0);
4582 }
4583
4584 if (arc_size > arc_c)
4585 (void) arc_adjust();
4586 }
4587
4588 typedef enum free_memory_reason_t {
4589 FMR_UNKNOWN,
4590 FMR_NEEDFREE,
4591 FMR_LOTSFREE,
4592 FMR_SWAPFS_MINFREE,
4593 FMR_PAGES_PP_MAXIMUM,
4594 FMR_HEAP_ARENA,
4595 FMR_ZIO_ARENA,
4596 } free_memory_reason_t;
4597
4598 int64_t last_free_memory;
4599 free_memory_reason_t last_free_reason;
4600
4601 /*
4602 * Additional reserve of pages for pp_reserve.
4603 */
4604 int64_t arc_pages_pp_reserve = 64;
4605
4606 /*
4607 * Additional reserve of pages for swapfs.
4608 */
4609 int64_t arc_swapfs_reserve = 64;
4610
4611 /*
4612 * Return the amount of memory that can be consumed before reclaim will be
4613 * needed. Positive if there is sufficient free memory, negative indicates
4614 * the amount of memory that needs to be freed up.
4615 */
4616 static int64_t
4617 arc_available_memory(void)
4618 {
4619 int64_t lowest = INT64_MAX;
4620 int64_t n;
4621 free_memory_reason_t r = FMR_UNKNOWN;
4622
4623 #ifdef _KERNEL
4624 if (needfree > 0) {
4625 n = PAGESIZE * (-needfree);
4626 if (n < lowest) {
4627 lowest = n;
4628 r = FMR_NEEDFREE;
4629 }
4630 }
4631
4632 /*
4633 * check that we're out of range of the pageout scanner. It starts to
4634 * schedule paging if freemem is less than lotsfree and needfree.
4635 * lotsfree is the high-water mark for pageout, and needfree is the
4636 * number of needed free pages. We add extra pages here to make sure
4637 * the scanner doesn't start up while we're freeing memory.
4638 */
4639 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
4640 if (n < lowest) {
4641 lowest = n;
4642 r = FMR_LOTSFREE;
4643 }
4644
4645 /*
4646 * check to make sure that swapfs has enough space so that anon
4647 * reservations can still succeed. anon_resvmem() checks that the
4648 * availrmem is greater than swapfs_minfree, and the number of reserved
4649 * swap pages. We also add a bit of extra here just to prevent
4650 * circumstances from getting really dire.
4651 */
4652 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
4653 desfree - arc_swapfs_reserve);
4654 if (n < lowest) {
4655 lowest = n;
4656 r = FMR_SWAPFS_MINFREE;
4657 }
4658
4659
4660 /*
4661 * Check that we have enough availrmem that memory locking (e.g., via
4662 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
4663 * stores the number of pages that cannot be locked; when availrmem
4664 * drops below pages_pp_maximum, page locking mechanisms such as
4665 * page_pp_lock() will fail.)
4666 */
4667 n = PAGESIZE * (availrmem - pages_pp_maximum -
4668 arc_pages_pp_reserve);
4669 if (n < lowest) {
4670 lowest = n;
4671 r = FMR_PAGES_PP_MAXIMUM;
4672 }
4673
4674 #if defined(__i386)
4675 /*
4676 * If we're on an i386 platform, it's possible that we'll exhaust the
4677 * kernel heap space before we ever run out of available physical
4678 * memory. Most checks of the size of the heap_area compare against
4679 * tune.t_minarmem, which is the minimum available real memory that we
4680 * can have in the system. However, this is generally fixed at 25 pages
4681 * which is so low that it's useless. In this comparison, we seek to
4682 * calculate the total heap-size, and reclaim if more than 3/4ths of the
4683 * heap is allocated. (Or, in the calculation, if less than 1/4th is
4684 * free)
4685 */
4686 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) -
4687 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
4688 if (n < lowest) {
4689 lowest = n;
4690 r = FMR_HEAP_ARENA;
4691 }
4692 #endif
4693
4694 /*
4695 * If zio data pages are being allocated out of a separate heap segment,
4696 * then enforce that the size of available vmem for this arena remains
4697 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free.
4698 *
4699 * Note that reducing the arc_zio_arena_free_shift keeps more virtual
4700 * memory (in the zio_arena) free, which can avoid memory
4701 * fragmentation issues.
4702 */
4703 if (zio_arena != NULL) {
4704 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
4705 (vmem_size(zio_arena, VMEM_ALLOC) >>
4706 arc_zio_arena_free_shift);
4707 if (n < lowest) {
4708 lowest = n;
4709 r = FMR_ZIO_ARENA;
4710 }
4711 }
4712 #else
4713 /* Every 100 calls, free a small amount */
4714 if (spa_get_random(100) == 0)
4715 lowest = -1024;
4716 #endif
4717
4718 last_free_memory = lowest;
4719 last_free_reason = r;
4720
4721 return (lowest);
4722 }
4723
4724
4725 /*
4726 * Determine if the system is under memory pressure and is asking
4727 * to reclaim memory. A return value of B_TRUE indicates that the system
4728 * is under memory pressure and that the arc should adjust accordingly.
4729 */
4730 static boolean_t
4731 arc_reclaim_needed(void)
4732 {
4733 return (arc_available_memory() < 0);
4734 }
4735
4736 static void
4737 arc_kmem_reap_now(void)
4738 {
4739 size_t i;
4740 kmem_cache_t *prev_cache = NULL;
4741 kmem_cache_t *prev_data_cache = NULL;
4742 extern kmem_cache_t *zio_buf_cache[];
4743 extern kmem_cache_t *zio_data_buf_cache[];
4744 extern kmem_cache_t *range_seg_cache;
4745 extern kmem_cache_t *abd_chunk_cache;
4746
4747 #ifdef _KERNEL
4748 if (arc_meta_used >= arc_meta_limit || arc_ddt_size >= arc_ddt_limit) {
4749 /*
4750 * We are exceeding our meta-data or DDT cache limit.
4751 * Purge some DNLC entries to release holds on meta-data/DDT.
4752 */
4753 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
4754 }
4755 #if defined(__i386)
4756 /*
4757 * Reclaim unused memory from all kmem caches.
4758 */
4759 kmem_reap();
4760 #endif
4761 #endif
4762
4763 /*
4764 * If a kmem reap is already active, don't schedule more. We must
4765 * check for this because kmem_cache_reap_soon() won't actually
4766 * block on the cache being reaped (this is to prevent callers from
4767 * becoming implicitly blocked by a system-wide kmem reap -- which,
4768 * on a system with many, many full magazines, can take minutes).
4769 */
4770 if (kmem_cache_reap_active())
4771 return;
4772
4773 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
4774 if (zio_buf_cache[i] != prev_cache) {
4775 prev_cache = zio_buf_cache[i];
4776 kmem_cache_reap_soon(zio_buf_cache[i]);
4777 }
4778 if (zio_data_buf_cache[i] != prev_data_cache) {
4779 prev_data_cache = zio_data_buf_cache[i];
4780 kmem_cache_reap_soon(zio_data_buf_cache[i]);
4781 }
4782 }
4783 kmem_cache_reap_soon(abd_chunk_cache);
4784 kmem_cache_reap_soon(buf_cache);
4785 kmem_cache_reap_soon(hdr_full_cache);
4786 kmem_cache_reap_soon(hdr_l2only_cache);
4787 kmem_cache_reap_soon(range_seg_cache);
4788
4789 if (zio_arena != NULL) {
4790 /*
4791 * Ask the vmem arena to reclaim unused memory from its
4792 * quantum caches.
4793 */
4794 vmem_qcache_reap(zio_arena);
4795 }
4796 }
4797
4798 /*
4799 * Threads can block in arc_get_data_impl() waiting for this thread to evict
4800 * enough data and signal them to proceed. When this happens, the threads in
4801 * arc_get_data_impl() are sleeping while holding the hash lock for their
4802 * particular arc header. Thus, we must be careful to never sleep on a
4803 * hash lock in this thread. This is to prevent the following deadlock:
4804 *
4805 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L",
4806 * waiting for the reclaim thread to signal it.
4807 *
4808 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
4809 * fails, and goes to sleep forever.
4810 *
4811 * This possible deadlock is avoided by always acquiring a hash lock
4812 * using mutex_tryenter() from arc_reclaim_thread().
4813 */
4814 /* ARGSUSED */
4815 static void
4816 arc_reclaim_thread(void *unused)
4817 {
4818 hrtime_t growtime = 0;
4819 hrtime_t kmem_reap_time = 0;
4820 callb_cpr_t cpr;
4821
4822 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
4823
4824 mutex_enter(&arc_reclaim_lock);
4825 while (!arc_reclaim_thread_exit) {
4826 uint64_t evicted = 0;
4827
4828 /*
4829 * This is necessary in order for the mdb ::arc dcmd to
4830 * show up to date information. Since the ::arc command
4831 * does not call the kstat's update function, without
4832 * this call, the command may show stale stats for the
4833 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
4834 * with this change, the data might be up to 1 second
4835 * out of date; but that should suffice. The arc_state_t
4836 * structures can be queried directly if more accurate
4837 * information is needed.
4838 */
4839 if (arc_ksp != NULL)
4840 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
4841
4842 mutex_exit(&arc_reclaim_lock);
4843
4844 /*
4845 * We call arc_adjust() before (possibly) calling
4846 * arc_kmem_reap_now(), so that we can wake up
4847 * arc_get_data_impl() sooner.
4848 */
4849 evicted = arc_adjust();
4850
4851 int64_t free_memory = arc_available_memory();
4852 if (free_memory < 0) {
4853 hrtime_t curtime = gethrtime();
4854 arc_no_grow = B_TRUE;
4855 arc_warm = B_TRUE;
4856
4857 /*
4858 * Wait at least zfs_grow_retry (default 60) seconds
4859 * before considering growing.
4860 */
4861 growtime = curtime + SEC2NSEC(arc_grow_retry);
4862
4863 /*
4864 * Wait at least arc_kmem_cache_reap_retry_ms
4865 * between arc_kmem_reap_now() calls. Without
4866 * this check it is possible to end up in a
4867 * situation where we spend lots of time
4868 * reaping caches, while we're near arc_c_min.
4869 */
4870 if (curtime >= kmem_reap_time) {
4871 arc_kmem_reap_now();
4872 kmem_reap_time = gethrtime() +
4873 MSEC2NSEC(arc_kmem_cache_reap_retry_ms);
4874 }
4875
4876 /*
4877 * If we are still low on memory, shrink the ARC
4878 * so that we have arc_shrink_min free space.
4879 */
4880 free_memory = arc_available_memory();
4881
4882 int64_t to_free =
4883 (arc_c >> arc_shrink_shift) - free_memory;
4884 if (to_free > 0) {
4885 #ifdef _KERNEL
4886 to_free = MAX(to_free, ptob(needfree));
4887 #endif
4888 arc_shrink(to_free);
4889 }
4890 } else if (free_memory < arc_c >> arc_no_grow_shift) {
4891 arc_no_grow = B_TRUE;
4892 } else if (gethrtime() >= growtime) {
4893 arc_no_grow = B_FALSE;
4894 }
4895
4896 mutex_enter(&arc_reclaim_lock);
4897
4898 /*
4899 * If evicted is zero, we couldn't evict anything via
4900 * arc_adjust(). This could be due to hash lock
4901 * collisions, but more likely due to the majority of
4902 * arc buffers being unevictable. Therefore, even if
4903 * arc_size is above arc_c, another pass is unlikely to
4904 * be helpful and could potentially cause us to enter an
4905 * infinite loop.
4906 */
4907 if (arc_size <= arc_c || evicted == 0) {
4908 /*
4909 * We're either no longer overflowing, or we
4910 * can't evict anything more, so we should wake
4911 * up any threads before we go to sleep.
4912 */
4913 cv_broadcast(&arc_reclaim_waiters_cv);
4914
4915 /*
4916 * Block until signaled, or after one second (we
4917 * might need to perform arc_kmem_reap_now()
4918 * even if we aren't being signalled)
4919 */
4920 CALLB_CPR_SAFE_BEGIN(&cpr);
4921 (void) cv_timedwait_hires(&arc_reclaim_thread_cv,
4922 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0);
4923 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
4924 }
4925 }
4926
4927 arc_reclaim_thread_exit = B_FALSE;
4928 cv_broadcast(&arc_reclaim_thread_cv);
4929 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
4930 thread_exit();
4931 }
4932
4933 /*
4934 * Adapt arc info given the number of bytes we are trying to add and
4935 * the state that we are comming from. This function is only called
4936 * when we are adding new content to the cache.
4937 */
4938 static void
4939 arc_adapt(int bytes, arc_state_t *state)
4940 {
4941 int mult;
4942 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
4943 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
4944 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
4945
4946 if (state == arc_l2c_only)
4947 return;
4948
4949 ASSERT(bytes > 0);
4950 /*
4951 * Adapt the target size of the MRU list:
4952 * - if we just hit in the MRU ghost list, then increase
4953 * the target size of the MRU list.
4954 * - if we just hit in the MFU ghost list, then increase
4955 * the target size of the MFU list by decreasing the
4956 * target size of the MRU list.
4957 */
4958 if (state == arc_mru_ghost) {
4959 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
4960 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
4961
4962 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
4963 } else if (state == arc_mfu_ghost) {
4964 uint64_t delta;
4965
4966 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
4967 mult = MIN(mult, 10);
4968
4969 delta = MIN(bytes * mult, arc_p);
4970 arc_p = MAX(arc_p_min, arc_p - delta);
4971 }
4972 ASSERT((int64_t)arc_p >= 0);
4973
4974 if (arc_reclaim_needed()) {
4975 cv_signal(&arc_reclaim_thread_cv);
4976 return;
4977 }
4978
4979 if (arc_no_grow)
4980 return;
4981
4982 if (arc_c >= arc_c_max)
4983 return;
4984
4985 /*
4986 * If we're within (2 * maxblocksize) bytes of the target
4987 * cache size, increment the target cache size
4988 */
4989 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
4990 atomic_add_64(&arc_c, (int64_t)bytes);
4991 if (arc_c > arc_c_max)
4992 arc_c = arc_c_max;
4993 else if (state == arc_anon)
4994 atomic_add_64(&arc_p, (int64_t)bytes);
4995 if (arc_p > arc_c)
4996 arc_p = arc_c;
4997 }
4998 ASSERT((int64_t)arc_p >= 0);
4999 }
5000
5001 /*
5002 * Check if arc_size has grown past our upper threshold, determined by
5003 * zfs_arc_overflow_shift.
5004 */
5005 static boolean_t
5006 arc_is_overflowing(void)
5007 {
5008 /* Always allow at least one block of overflow */
5009 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
5010 arc_c >> zfs_arc_overflow_shift);
5011
5012 return (arc_size >= arc_c + overflow);
5013 }
5014
5015 static abd_t *
5016 arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5017 {
5018 arc_buf_contents_t type = arc_buf_type(hdr);
5019
5020 arc_get_data_impl(hdr, size, tag);
5021 if (type == ARC_BUFC_METADATA || type == ARC_BUFC_DDT) {
5022 return (abd_alloc(size, B_TRUE));
5023 } else {
5024 ASSERT(type == ARC_BUFC_DATA);
5025 return (abd_alloc(size, B_FALSE));
5026 }
5027 }
5028
5029 static void *
5030 arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5031 {
5032 arc_buf_contents_t type = arc_buf_type(hdr);
5033
5034 arc_get_data_impl(hdr, size, tag);
5035 if (type == ARC_BUFC_METADATA || type == ARC_BUFC_DDT) {
5036 return (zio_buf_alloc(size));
5037 } else {
5038 ASSERT(type == ARC_BUFC_DATA);
5039 return (zio_data_buf_alloc(size));
5040 }
5041 }
5042
5043 /*
5044 * Allocate a block and return it to the caller. If we are hitting the
5045 * hard limit for the cache size, we must sleep, waiting for the eviction
5046 * thread to catch up. If we're past the target size but below the hard
5047 * limit, we'll only signal the reclaim thread and continue on.
5048 */
5049 static void
5050 arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5051 {
5052 arc_state_t *state = hdr->b_l1hdr.b_state;
5053 arc_buf_contents_t type = arc_buf_type(hdr);
5054
5055 arc_adapt(size, state);
5056
5057 /*
5058 * If arc_size is currently overflowing, and has grown past our
5059 * upper limit, we must be adding data faster than the evict
5060 * thread can evict. Thus, to ensure we don't compound the
5061 * problem by adding more data and forcing arc_size to grow even
5062 * further past it's target size, we halt and wait for the
5063 * eviction thread to catch up.
5064 *
5065 * It's also possible that the reclaim thread is unable to evict
5066 * enough buffers to get arc_size below the overflow limit (e.g.
5067 * due to buffers being un-evictable, or hash lock collisions).
5068 * In this case, we want to proceed regardless if we're
5069 * overflowing; thus we don't use a while loop here.
5070 */
5071 if (arc_is_overflowing()) {
5072 mutex_enter(&arc_reclaim_lock);
5073
5074 /*
5075 * Now that we've acquired the lock, we may no longer be
5076 * over the overflow limit, lets check.
5077 *
5078 * We're ignoring the case of spurious wake ups. If that
5079 * were to happen, it'd let this thread consume an ARC
5080 * buffer before it should have (i.e. before we're under
5081 * the overflow limit and were signalled by the reclaim
5082 * thread). As long as that is a rare occurrence, it
5083 * shouldn't cause any harm.
5084 */
5085 if (arc_is_overflowing()) {
5086 cv_signal(&arc_reclaim_thread_cv);
5087 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
5088 }
5089
5090 mutex_exit(&arc_reclaim_lock);
5091 }
5092
5093 VERIFY3U(hdr->b_type, ==, type);
5094 if (type == ARC_BUFC_DDT) {
5095 arc_space_consume(size, ARC_SPACE_DDT);
5096 } else if (type == ARC_BUFC_METADATA) {
5097 arc_space_consume(size, ARC_SPACE_META);
5098 } else {
5099 arc_space_consume(size, ARC_SPACE_DATA);
5100 }
5101
5102 /*
5103 * Update the state size. Note that ghost states have a
5104 * "ghost size" and so don't need to be updated.
5105 */
5106 if (!GHOST_STATE(state)) {
5107
5108 (void) refcount_add_many(&state->arcs_size, size, tag);
5109
5110 /*
5111 * If this is reached via arc_read, the link is
5112 * protected by the hash lock. If reached via
5113 * arc_buf_alloc, the header should not be accessed by
5114 * any other thread. And, if reached via arc_read_done,
5115 * the hash lock will protect it if it's found in the
5116 * hash table; otherwise no other thread should be
5117 * trying to [add|remove]_reference it.
5118 */
5119 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
5120 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5121 (void) refcount_add_many(&state->arcs_esize[type],
5122 size, tag);
5123 }
5124
5125 /*
5126 * If we are growing the cache, and we are adding anonymous
5127 * data, and we have outgrown arc_p, update arc_p
5128 */
5129 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon &&
5130 (refcount_count(&arc_anon->arcs_size) +
5131 refcount_count(&arc_mru->arcs_size) > arc_p))
5132 arc_p = MIN(arc_c, arc_p + size);
5133 }
5134 }
5135
5136 static void
5137 arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag)
5138 {
5139 arc_free_data_impl(hdr, size, tag);
5140 abd_free(abd);
5141 }
5142
5143 static void
5144 arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag)
5145 {
5146 arc_buf_contents_t type = arc_buf_type(hdr);
5147
5148 arc_free_data_impl(hdr, size, tag);
5149 if (type == ARC_BUFC_METADATA || type == ARC_BUFC_DDT) {
5150 zio_buf_free(buf, size);
5151 } else {
5152 ASSERT(type == ARC_BUFC_DATA);
5153 zio_data_buf_free(buf, size);
5154 }
5155 }
5156
5157 /*
5158 * Free the arc data buffer.
5159 */
5160 static void
5161 arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5162 {
5163 arc_state_t *state = hdr->b_l1hdr.b_state;
5164 arc_buf_contents_t type = arc_buf_type(hdr);
5165
5166 /* protected by hash lock, if in the hash table */
5167 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
5168 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5169 ASSERT(state != arc_anon && state != arc_l2c_only);
5170
5171 (void) refcount_remove_many(&state->arcs_esize[type],
5172 size, tag);
5173 }
5174 (void) refcount_remove_many(&state->arcs_size, size, tag);
5175
5176 VERIFY3U(hdr->b_type, ==, type);
5177 if (type == ARC_BUFC_DDT) {
5178 arc_space_return(size, ARC_SPACE_DDT);
5179 } else if (type == ARC_BUFC_METADATA) {
5180 arc_space_return(size, ARC_SPACE_META);
5181 } else {
5182 ASSERT(type == ARC_BUFC_DATA);
5183 arc_space_return(size, ARC_SPACE_DATA);
5184 }
5185 }
5186
5187 /*
5188 * This routine is called whenever a buffer is accessed.
5189 * NOTE: the hash lock is dropped in this function.
5190 */
5191 static void
5192 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
5193 {
5194 clock_t now;
5195
5196 ASSERT(MUTEX_HELD(hash_lock));
5197 ASSERT(HDR_HAS_L1HDR(hdr));
5198
5199 if (hdr->b_l1hdr.b_state == arc_anon) {
5200 /*
5201 * This buffer is not in the cache, and does not
5202 * appear in our "ghost" list. Add the new buffer
5203 * to the MRU state.
5204 */
5205
5206 ASSERT0(hdr->b_l1hdr.b_arc_access);
5207 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5208 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5209 arc_change_state(arc_mru, hdr, hash_lock);
5210
5211 } else if (hdr->b_l1hdr.b_state == arc_mru) {
5212 now = ddi_get_lbolt();
5213
5214 /*
5215 * If this buffer is here because of a prefetch, then either:
5216 * - clear the flag if this is a "referencing" read
5217 * (any subsequent access will bump this into the MFU state).
5218 * or
5219 * - move the buffer to the head of the list if this is
5220 * another prefetch (to make it less likely to be evicted).
5221 */
5222 if (HDR_PREFETCH(hdr)) {
5223 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
5224 /* link protected by hash lock */
5225 ASSERT(multilist_link_active(
5226 &hdr->b_l1hdr.b_arc_node));
5227 } else {
5228 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
5229 ARCSTAT_BUMP(arcstat_mru_hits);
5230 }
5231 hdr->b_l1hdr.b_arc_access = now;
5232 return;
5233 }
5234
5235 /*
5236 * This buffer has been "accessed" only once so far,
5237 * but it is still in the cache. Move it to the MFU
5238 * state.
5239 */
5240 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
5241 /*
5242 * More than 125ms have passed since we
5243 * instantiated this buffer. Move it to the
5244 * most frequently used state.
5245 */
5246 hdr->b_l1hdr.b_arc_access = now;
5247 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5248 arc_change_state(arc_mfu, hdr, hash_lock);
5249 }
5250 ARCSTAT_BUMP(arcstat_mru_hits);
5251 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
5252 arc_state_t *new_state;
5253 /*
5254 * This buffer has been "accessed" recently, but
5255 * was evicted from the cache. Move it to the
5256 * MFU state.
5257 */
5258
5259 if (HDR_PREFETCH(hdr)) {
5260 new_state = arc_mru;
5261 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0)
5262 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
5263 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5264 } else {
5265 new_state = arc_mfu;
5266 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5267 }
5268
5269 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5270 arc_change_state(new_state, hdr, hash_lock);
5271
5272 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
5273 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
5274 /*
5275 * This buffer has been accessed more than once and is
5276 * still in the cache. Keep it in the MFU state.
5277 *
5278 * NOTE: an add_reference() that occurred when we did
5279 * the arc_read() will have kicked this off the list.
5280 * If it was a prefetch, we will explicitly move it to
5281 * the head of the list now.
5282 */
5283 if ((HDR_PREFETCH(hdr)) != 0) {
5284 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5285 /* link protected by hash_lock */
5286 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node));
5287 }
5288 ARCSTAT_BUMP(arcstat_mfu_hits);
5289 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5290 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
5291 arc_state_t *new_state = arc_mfu;
5292 /*
5293 * This buffer has been accessed more than once but has
5294 * been evicted from the cache. Move it back to the
5295 * MFU state.
5296 */
5297
5298 if (HDR_PREFETCH(hdr)) {
5299 /*
5300 * This is a prefetch access...
5301 * move this block back to the MRU state.
5302 */
5303 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
5304 new_state = arc_mru;
5305 }
5306
5307 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5308 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5309 arc_change_state(new_state, hdr, hash_lock);
5310
5311 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
5312 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
5313 /*
5314 * This buffer is on the 2nd Level ARC.
5315 */
5316
5317 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5318 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5319 arc_change_state(arc_mfu, hdr, hash_lock);
5320 } else {
5321 ASSERT(!"invalid arc state");
5322 }
5323 }
5324
5325 /*
5326 * This routine is called by dbuf_hold() to update the arc_access() state
5327 * which otherwise would be skipped for entries in the dbuf cache.
5328 */
5329 void
5330 arc_buf_access(arc_buf_t *buf)
5331 {
5332 mutex_enter(&buf->b_evict_lock);
5333 arc_buf_hdr_t *hdr = buf->b_hdr;
5334
5335 /*
5336 * Avoid taking the hash_lock when possible as an optimization.
5337 * The header must be checked again under the hash_lock in order
5338 * to handle the case where it is concurrently being released.
5339 */
5340 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5341 mutex_exit(&buf->b_evict_lock);
5342 return;
5343 }
5344
5345 kmutex_t *hash_lock = HDR_LOCK(hdr);
5346 mutex_enter(hash_lock);
5347
5348 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5349 mutex_exit(hash_lock);
5350 mutex_exit(&buf->b_evict_lock);
5351 ARCSTAT_BUMP(arcstat_access_skip);
5352 return;
5353 }
5354
5355 mutex_exit(&buf->b_evict_lock);
5356
5357 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5358 hdr->b_l1hdr.b_state == arc_mfu);
5359
5360 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5361 arc_access(hdr, hash_lock);
5362 mutex_exit(hash_lock);
5363
5364 ARCSTAT_BUMP(arcstat_hits);
5365 /*
5366 * Upstream used the ARCSTAT_CONDSTAT macro here, but they changed
5367 * the argument format for that macro, which would requie that we
5368 * go and modify all other uses of it. So it's easier to just expand
5369 * this one invocation of the macro to do the right thing.
5370 */
5371 if (!HDR_PREFETCH(hdr)) {
5372 if (!HDR_ISTYPE_METADATA(hdr))
5373 ARCSTAT_BUMP(arcstat_demand_data_hits);
5374 else
5375 ARCSTAT_BUMP(arcstat_demand_metadata_hits);
5376 } else {
5377 if (!HDR_ISTYPE_METADATA(hdr))
5378 ARCSTAT_BUMP(arcstat_prefetch_data_hits);
5379 else
5380 ARCSTAT_BUMP(arcstat_prefetch_metadata_hits);
5381 }
5382 }
5383
5384 /* a generic arc_done_func_t which you can use */
5385 /* ARGSUSED */
5386 void
5387 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
5388 {
5389 if (zio == NULL || zio->io_error == 0)
5390 bcopy(buf->b_data, arg, arc_buf_size(buf));
5391 arc_buf_destroy(buf, arg);
5392 }
5393
5394 /* a generic arc_done_func_t */
5395 void
5396 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
5397 {
5398 arc_buf_t **bufp = arg;
5399 if (zio && zio->io_error) {
5400 arc_buf_destroy(buf, arg);
5401 *bufp = NULL;
5402 } else {
5403 *bufp = buf;
5404 ASSERT(buf->b_data);
5405 }
5406 }
5407
5408 static void
5409 arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp)
5410 {
5411 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
5412 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
5413 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
5414 } else {
5415 if (HDR_COMPRESSION_ENABLED(hdr)) {
5416 ASSERT3U(HDR_GET_COMPRESS(hdr), ==,
5417 BP_GET_COMPRESS(bp));
5418 }
5419 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
5420 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
5421 }
5422 }
5423
5424 static void
5425 arc_read_done(zio_t *zio)
5426 {
5427 arc_buf_hdr_t *hdr = zio->io_private;
5428 kmutex_t *hash_lock = NULL;
5429 arc_callback_t *callback_list;
5430 arc_callback_t *acb;
5431 boolean_t freeable = B_FALSE;
5432 boolean_t no_zio_error = (zio->io_error == 0);
5433
5434 /*
5435 * The hdr was inserted into hash-table and removed from lists
5436 * prior to starting I/O. We should find this header, since
5437 * it's in the hash table, and it should be legit since it's
5438 * not possible to evict it during the I/O. The only possible
5439 * reason for it not to be found is if we were freed during the
5440 * read.
5441 */
5442 if (HDR_IN_HASH_TABLE(hdr)) {
5443 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
5444 ASSERT3U(hdr->b_dva.dva_word[0], ==,
5445 BP_IDENTITY(zio->io_bp)->dva_word[0]);
5446 ASSERT3U(hdr->b_dva.dva_word[1], ==,
5447 BP_IDENTITY(zio->io_bp)->dva_word[1]);
5448
5449 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
5450 &hash_lock);
5451
5452 ASSERT((found == hdr &&
5453 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
5454 (found == hdr && HDR_L2_READING(hdr)));
5455 ASSERT3P(hash_lock, !=, NULL);
5456 }
5457
5458 if (no_zio_error) {
5459 /* byteswap if necessary */
5460 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
5461 if (BP_GET_LEVEL(zio->io_bp) > 0) {
5462 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
5463 } else {
5464 hdr->b_l1hdr.b_byteswap =
5465 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
5466 }
5467 } else {
5468 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
5469 }
5470 }
5471
5472 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
5473 if (l2arc_noprefetch && HDR_PREFETCH(hdr))
5474 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE);
5475
5476 callback_list = hdr->b_l1hdr.b_acb;
5477 ASSERT3P(callback_list, !=, NULL);
5478
5479 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) {
5480 /*
5481 * Only call arc_access on anonymous buffers. This is because
5482 * if we've issued an I/O for an evicted buffer, we've already
5483 * called arc_access (to prevent any simultaneous readers from
5484 * getting confused).
5485 */
5486 arc_access(hdr, hash_lock);
5487 }
5488
5489 /*
5490 * If a read request has a callback (i.e. acb_done is not NULL), then we
5491 * make a buf containing the data according to the parameters which were
5492 * passed in. The implementation of arc_buf_alloc_impl() ensures that we
5493 * aren't needlessly decompressing the data multiple times.
5494 */
5495 int callback_cnt = 0;
5496 for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
5497 if (!acb->acb_done)
5498 continue;
5499
5500 /* This is a demand read since prefetches don't use callbacks */
5501 callback_cnt++;
5502
5503 int error = arc_buf_alloc_impl(hdr, acb->acb_private,
5504 acb->acb_compressed, no_zio_error, &acb->acb_buf);
5505 if (no_zio_error) {
5506 zio->io_error = error;
5507 }
5508 }
5509 hdr->b_l1hdr.b_acb = NULL;
5510 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5511 if (callback_cnt == 0) {
5512 ASSERT(HDR_PREFETCH(hdr));
5513 ASSERT0(hdr->b_l1hdr.b_bufcnt);
5514 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5515 }
5516
5517 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
5518 callback_list != NULL);
5519
5520 if (no_zio_error) {
5521 arc_hdr_verify(hdr, zio->io_bp);
5522 } else {
5523 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
5524 if (hdr->b_l1hdr.b_state != arc_anon)
5525 arc_change_state(arc_anon, hdr, hash_lock);
5526 if (HDR_IN_HASH_TABLE(hdr)) {
5527 if (hash_lock)
5528 arc_wait_for_krrp(hdr);
5529 buf_hash_remove(hdr);
5530 }
5531 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5532 }
5533
5534 /*
5535 * Broadcast before we drop the hash_lock to avoid the possibility
5536 * that the hdr (and hence the cv) might be freed before we get to
5537 * the cv_broadcast().
5538 */
5539 cv_broadcast(&hdr->b_l1hdr.b_cv);
5540
5541 if (hash_lock != NULL) {
5542 mutex_exit(hash_lock);
5543 } else {
5544 /*
5545 * This block was freed while we waited for the read to
5546 * complete. It has been removed from the hash table and
5547 * moved to the anonymous state (so that it won't show up
5548 * in the cache).
5549 */
5550 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
5551 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5552 }
5553
5554 /* execute each callback and free its structure */
5555 while ((acb = callback_list) != NULL) {
5556 if (acb->acb_done)
5557 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
5558
5559 if (acb->acb_zio_dummy != NULL) {
5560 acb->acb_zio_dummy->io_error = zio->io_error;
5561 zio_nowait(acb->acb_zio_dummy);
5562 }
5563
5564 callback_list = acb->acb_next;
5565 kmem_free(acb, sizeof (arc_callback_t));
5566 }
5567
5568 if (freeable)
5569 arc_hdr_destroy(hdr);
5570 }
5571
5572 /*
5573 * The function to process data from arc by a callback
5574 * The main purpose is to directly copy data from arc to a target buffer
5575 */
5576 int
5577 arc_io_bypass(spa_t *spa, const blkptr_t *bp,
5578 arc_bypass_io_func func, void *arg)
5579 {
5580 arc_buf_hdr_t *hdr;
5581 kmutex_t *hash_lock = NULL;
5582 int error = 0;
5583 uint64_t guid = spa_load_guid(spa);
5584
5585 top:
5586 hdr = buf_hash_find(guid, bp, &hash_lock);
5587 if (hdr && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_bufcnt > 0 &&
5588 hdr->b_l1hdr.b_buf->b_data) {
5589 if (HDR_IO_IN_PROGRESS(hdr)) {
5590 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5591 mutex_exit(hash_lock);
5592 DTRACE_PROBE(arc_bypass_wait);
5593 goto top;
5594 }
5595
5596 /*
5597 * As the func is an arbitrary callback, which can block, lock
5598 * should be released not to block other threads from
5599 * performing. A counter is used to hold a reference to block
5600 * which are held by krrp.
5601 */
5602
5603 hdr->b_l1hdr.b_krrp++;
5604 mutex_exit(hash_lock);
5605
5606 error = func(hdr->b_l1hdr.b_buf->b_data, hdr->b_lsize, arg);
5607
5608 mutex_enter(hash_lock);
5609 hdr->b_l1hdr.b_krrp--;
5610 cv_broadcast(&hdr->b_l1hdr.b_cv);
5611 mutex_exit(hash_lock);
5612
5613 return (error);
5614 } else {
5615 if (hash_lock)
5616 mutex_exit(hash_lock);
5617 return (ENODATA);
5618 }
5619 }
5620
5621 /*
5622 * "Read" the block at the specified DVA (in bp) via the
5623 * cache. If the block is found in the cache, invoke the provided
5624 * callback immediately and return. Note that the `zio' parameter
5625 * in the callback will be NULL in this case, since no IO was
5626 * required. If the block is not in the cache pass the read request
5627 * on to the spa with a substitute callback function, so that the
5628 * requested block will be added to the cache.
5629 *
5630 * If a read request arrives for a block that has a read in-progress,
5631 * either wait for the in-progress read to complete (and return the
5632 * results); or, if this is a read with a "done" func, add a record
5633 * to the read to invoke the "done" func when the read completes,
5634 * and return; or just return.
5635 *
5636 * arc_read_done() will invoke all the requested "done" functions
5637 * for readers of this block.
5638 */
5639 int
5640 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
5641 void *private, zio_priority_t priority, int zio_flags,
5642 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
5643 {
5644 arc_buf_hdr_t *hdr = NULL;
5645 kmutex_t *hash_lock = NULL;
5646 zio_t *rzio;
5647 uint64_t guid = spa_load_guid(spa);
5648 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0;
5649
5650 ASSERT(!BP_IS_EMBEDDED(bp) ||
5651 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
5652
5653 top:
5654 if (!BP_IS_EMBEDDED(bp)) {
5655 /*
5656 * Embedded BP's have no DVA and require no I/O to "read".
5657 * Create an anonymous arc buf to back it.
5658 */
5659 hdr = buf_hash_find(guid, bp, &hash_lock);
5660 }
5661
5662 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) {
5663 arc_buf_t *buf = NULL;
5664 *arc_flags |= ARC_FLAG_CACHED;
5665
5666 if (HDR_IO_IN_PROGRESS(hdr)) {
5667
5668 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
5669 priority == ZIO_PRIORITY_SYNC_READ) {
5670 /*
5671 * This sync read must wait for an
5672 * in-progress async read (e.g. a predictive
5673 * prefetch). Async reads are queued
5674 * separately at the vdev_queue layer, so
5675 * this is a form of priority inversion.
5676 * Ideally, we would "inherit" the demand
5677 * i/o's priority by moving the i/o from
5678 * the async queue to the synchronous queue,
5679 * but there is currently no mechanism to do
5680 * so. Track this so that we can evaluate
5681 * the magnitude of this potential performance
5682 * problem.
5683 *
5684 * Note that if the prefetch i/o is already
5685 * active (has been issued to the device),
5686 * the prefetch improved performance, because
5687 * we issued it sooner than we would have
5688 * without the prefetch.
5689 */
5690 DTRACE_PROBE1(arc__sync__wait__for__async,
5691 arc_buf_hdr_t *, hdr);
5692 ARCSTAT_BUMP(arcstat_sync_wait_for_async);
5693 }
5694 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5695 arc_hdr_clear_flags(hdr,
5696 ARC_FLAG_PREDICTIVE_PREFETCH);
5697 }
5698
5699 if (*arc_flags & ARC_FLAG_WAIT) {
5700 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5701 mutex_exit(hash_lock);
5702 goto top;
5703 }
5704 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5705
5706 if (done) {
5707 arc_callback_t *acb = NULL;
5708
5709 acb = kmem_zalloc(sizeof (arc_callback_t),
5710 KM_SLEEP);
5711 acb->acb_done = done;
5712 acb->acb_private = private;
5713 acb->acb_compressed = compressed_read;
5714 if (pio != NULL)
5715 acb->acb_zio_dummy = zio_null(pio,
5716 spa, NULL, NULL, NULL, zio_flags);
5717
5718 ASSERT3P(acb->acb_done, !=, NULL);
5719 acb->acb_next = hdr->b_l1hdr.b_acb;
5720 hdr->b_l1hdr.b_acb = acb;
5721 mutex_exit(hash_lock);
5722 return (0);
5723 }
5724 mutex_exit(hash_lock);
5725 return (0);
5726 }
5727
5728 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5729 hdr->b_l1hdr.b_state == arc_mfu);
5730
5731 if (done) {
5732 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5733 /*
5734 * This is a demand read which does not have to
5735 * wait for i/o because we did a predictive
5736 * prefetch i/o for it, which has completed.
5737 */
5738 DTRACE_PROBE1(
5739 arc__demand__hit__predictive__prefetch,
5740 arc_buf_hdr_t *, hdr);
5741 ARCSTAT_BUMP(
5742 arcstat_demand_hit_predictive_prefetch);
5743 arc_hdr_clear_flags(hdr,
5744 ARC_FLAG_PREDICTIVE_PREFETCH);
5745 }
5746 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
5747
5748 /* Get a buf with the desired data in it. */
5749 VERIFY0(arc_buf_alloc_impl(hdr, private,
5750 compressed_read, B_TRUE, &buf));
5751 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
5752 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
5753 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5754 }
5755 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5756 arc_access(hdr, hash_lock);
5757 if (*arc_flags & ARC_FLAG_L2CACHE)
5758 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5759 mutex_exit(hash_lock);
5760 ARCSTAT_BUMP(arcstat_hits);
5761 if (HDR_ISTYPE_DDT(hdr))
5762 ARCSTAT_BUMP(arcstat_ddt_hits);
5763 arc_update_hit_stat(hdr, B_TRUE);
5764
5765 if (done)
5766 done(NULL, buf, private);
5767 } else {
5768 uint64_t lsize = BP_GET_LSIZE(bp);
5769 uint64_t psize = BP_GET_PSIZE(bp);
5770 arc_callback_t *acb;
5771 vdev_t *vd = NULL;
5772 uint64_t addr = 0;
5773 boolean_t devw = B_FALSE;
5774 uint64_t size;
5775
5776 if (hdr == NULL) {
5777 /* this block is not in the cache */
5778 arc_buf_hdr_t *exists = NULL;
5779 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
5780 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
5781 BP_GET_COMPRESS(bp), type);
5782
5783 if (!BP_IS_EMBEDDED(bp)) {
5784 hdr->b_dva = *BP_IDENTITY(bp);
5785 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
5786 exists = buf_hash_insert(hdr, &hash_lock);
5787 }
5788 if (exists != NULL) {
5789 /* somebody beat us to the hash insert */
5790 arc_hdr_destroy(hdr);
5791 mutex_exit(hash_lock);
5792 goto top; /* restart the IO request */
5793 }
5794 } else {
5795 /*
5796 * This block is in the ghost cache. If it was L2-only
5797 * (and thus didn't have an L1 hdr), we realloc the
5798 * header to add an L1 hdr.
5799 */
5800 if (!HDR_HAS_L1HDR(hdr)) {
5801 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
5802 hdr_full_cache);
5803 }
5804 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5805 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
5806 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5807 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5808 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
5809 ASSERT3P(hdr->b_freeze_cksum, ==, NULL);
5810
5811 /*
5812 * This is a delicate dance that we play here.
5813 * This hdr is in the ghost list so we access it
5814 * to move it out of the ghost list before we
5815 * initiate the read. If it's a prefetch then
5816 * it won't have a callback so we'll remove the
5817 * reference that arc_buf_alloc_impl() created. We
5818 * do this after we've called arc_access() to
5819 * avoid hitting an assert in remove_reference().
5820 */
5821 arc_access(hdr, hash_lock);
5822 arc_hdr_alloc_pabd(hdr);
5823 }
5824 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5825 size = arc_hdr_size(hdr);
5826
5827 /*
5828 * If compression is enabled on the hdr, then will do
5829 * RAW I/O and will store the compressed data in the hdr's
5830 * data block. Otherwise, the hdr's data block will contain
5831 * the uncompressed data.
5832 */
5833 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
5834 zio_flags |= ZIO_FLAG_RAW;
5835 }
5836
5837 if (*arc_flags & ARC_FLAG_PREFETCH)
5838 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5839 if (*arc_flags & ARC_FLAG_L2CACHE)
5840 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5841 if (BP_GET_LEVEL(bp) > 0)
5842 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
5843 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
5844 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
5845 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
5846
5847 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
5848 acb->acb_done = done;
5849 acb->acb_private = private;
5850 acb->acb_compressed = compressed_read;
5851
5852 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5853 hdr->b_l1hdr.b_acb = acb;
5854 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5855
5856 if (HDR_HAS_L2HDR(hdr) &&
5857 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
5858 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
5859 addr = hdr->b_l2hdr.b_daddr;
5860 /*
5861 * Lock out device removal.
5862 */
5863 if (vdev_is_dead(vd) ||
5864 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
5865 vd = NULL;
5866 }
5867
5868 if (priority == ZIO_PRIORITY_ASYNC_READ)
5869 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5870 else
5871 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5872
5873 if (hash_lock != NULL)
5874 mutex_exit(hash_lock);
5875
5876 /*
5877 * At this point, we have a level 1 cache miss. Try again in
5878 * L2ARC if possible.
5879 */
5880 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
5881
5882 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
5883 uint64_t, lsize, zbookmark_phys_t *, zb);
5884 ARCSTAT_BUMP(arcstat_misses);
5885 arc_update_hit_stat(hdr, B_FALSE);
5886
5887 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
5888 /*
5889 * Read from the L2ARC if the following are true:
5890 * 1. The L2ARC vdev was previously cached.
5891 * 2. This buffer still has L2ARC metadata.
5892 * 3. This buffer isn't currently writing to the L2ARC.
5893 * 4. The L2ARC entry wasn't evicted, which may
5894 * also have invalidated the vdev.
5895 * 5. This isn't prefetch and l2arc_noprefetch is set.
5896 */
5897 if (HDR_HAS_L2HDR(hdr) &&
5898 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
5899 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
5900 l2arc_read_callback_t *cb;
5901 abd_t *abd;
5902 uint64_t asize;
5903
5904 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
5905 ARCSTAT_BUMP(arcstat_l2_hits);
5906 if (vdev_type_is_ddt(vd))
5907 ARCSTAT_BUMP(arcstat_l2_ddt_hits);
5908
5909 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
5910 KM_SLEEP);
5911 cb->l2rcb_hdr = hdr;
5912 cb->l2rcb_bp = *bp;
5913 cb->l2rcb_zb = *zb;
5914 cb->l2rcb_flags = zio_flags;
5915
5916 asize = vdev_psize_to_asize(vd, size);
5917 if (asize != size) {
5918 abd = abd_alloc_for_io(asize,
5919 !HDR_ISTYPE_DATA(hdr));
5920 cb->l2rcb_abd = abd;
5921 } else {
5922 abd = hdr->b_l1hdr.b_pabd;
5923 }
5924
5925 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
5926 addr + asize <= vd->vdev_psize -
5927 VDEV_LABEL_END_SIZE);
5928
5929 /*
5930 * l2arc read. The SCL_L2ARC lock will be
5931 * released by l2arc_read_done().
5932 * Issue a null zio if the underlying buffer
5933 * was squashed to zero size by compression.
5934 */
5935 ASSERT3U(HDR_GET_COMPRESS(hdr), !=,
5936 ZIO_COMPRESS_EMPTY);
5937 rzio = zio_read_phys(pio, vd, addr,
5938 asize, abd,
5939 ZIO_CHECKSUM_OFF,
5940 l2arc_read_done, cb, priority,
5941 zio_flags | ZIO_FLAG_DONT_CACHE |
5942 ZIO_FLAG_CANFAIL |
5943 ZIO_FLAG_DONT_PROPAGATE |
5944 ZIO_FLAG_DONT_RETRY, B_FALSE);
5945 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
5946 zio_t *, rzio);
5947
5948 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
5949 if (vdev_type_is_ddt(vd))
5950 ARCSTAT_INCR(arcstat_l2_ddt_read_bytes,
5951 size);
5952
5953 if (*arc_flags & ARC_FLAG_NOWAIT) {
5954 zio_nowait(rzio);
5955 return (0);
5956 }
5957
5958 ASSERT(*arc_flags & ARC_FLAG_WAIT);
5959 if (zio_wait(rzio) == 0)
5960 return (0);
5961
5962 /* l2arc read error; goto zio_read() */
5963 } else {
5964 DTRACE_PROBE1(l2arc__miss,
5965 arc_buf_hdr_t *, hdr);
5966 ARCSTAT_BUMP(arcstat_l2_misses);
5967 if (HDR_L2_WRITING(hdr))
5968 ARCSTAT_BUMP(arcstat_l2_rw_clash);
5969 spa_config_exit(spa, SCL_L2ARC, vd);
5970 }
5971 } else {
5972 if (vd != NULL)
5973 spa_config_exit(spa, SCL_L2ARC, vd);
5974 if (l2arc_ndev != 0) {
5975 DTRACE_PROBE1(l2arc__miss,
5976 arc_buf_hdr_t *, hdr);
5977 ARCSTAT_BUMP(arcstat_l2_misses);
5978 }
5979 }
5980
5981 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size,
5982 arc_read_done, hdr, priority, zio_flags, zb);
5983
5984 if (*arc_flags & ARC_FLAG_WAIT)
5985 return (zio_wait(rzio));
5986
5987 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5988 zio_nowait(rzio);
5989 }
5990 return (0);
5991 }
5992
5993 /*
5994 * Notify the arc that a block was freed, and thus will never be used again.
5995 */
5996 void
5997 arc_freed(spa_t *spa, const blkptr_t *bp)
5998 {
5999 arc_buf_hdr_t *hdr;
6000 kmutex_t *hash_lock;
6001 uint64_t guid = spa_load_guid(spa);
6002
6003 ASSERT(!BP_IS_EMBEDDED(bp));
6004
6005 hdr = buf_hash_find(guid, bp, &hash_lock);
6006 if (hdr == NULL)
6007 return;
6008
6009 /*
6010 * We might be trying to free a block that is still doing I/O
6011 * (i.e. prefetch) or has a reference (i.e. a dedup-ed,
6012 * dmu_sync-ed block). If this block is being prefetched, then it
6013 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
6014 * until the I/O completes. A block may also have a reference if it is
6015 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would
6016 * have written the new block to its final resting place on disk but
6017 * without the dedup flag set. This would have left the hdr in the MRU
6018 * state and discoverable. When the txg finally syncs it detects that
6019 * the block was overridden in open context and issues an override I/O.
6020 * Since this is a dedup block, the override I/O will determine if the
6021 * block is already in the DDT. If so, then it will replace the io_bp
6022 * with the bp from the DDT and allow the I/O to finish. When the I/O
6023 * reaches the done callback, dbuf_write_override_done, it will
6024 * check to see if the io_bp and io_bp_override are identical.
6025 * If they are not, then it indicates that the bp was replaced with
6026 * the bp in the DDT and the override bp is freed. This allows
6027 * us to arrive here with a reference on a block that is being
6028 * freed. So if we have an I/O in progress, or a reference to
6029 * this hdr, then we don't destroy the hdr.
6030 */
6031 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
6032 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
6033 arc_change_state(arc_anon, hdr, hash_lock);
6034 arc_hdr_destroy(hdr);
6035 mutex_exit(hash_lock);
6036 } else {
6037 mutex_exit(hash_lock);
6038 }
6039
6040 }
6041
6042 /*
6043 * Release this buffer from the cache, making it an anonymous buffer. This
6044 * must be done after a read and prior to modifying the buffer contents.
6045 * If the buffer has more than one reference, we must make
6046 * a new hdr for the buffer.
6047 */
6048 void
6049 arc_release(arc_buf_t *buf, void *tag)
6050 {
6051 arc_buf_hdr_t *hdr = buf->b_hdr;
6052
6053 /*
6054 * It would be nice to assert that if it's DMU metadata (level >
6055 * 0 || it's the dnode file), then it must be syncing context.
6056 * But we don't know that information at this level.
6057 */
6058
6059 mutex_enter(&buf->b_evict_lock);
6060
6061 ASSERT(HDR_HAS_L1HDR(hdr));
6062
6063 /*
6064 * We don't grab the hash lock prior to this check, because if
6065 * the buffer's header is in the arc_anon state, it won't be
6066 * linked into the hash table.
6067 */
6068 if (hdr->b_l1hdr.b_state == arc_anon) {
6069 mutex_exit(&buf->b_evict_lock);
6070 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6071 ASSERT(!HDR_IN_HASH_TABLE(hdr));
6072 ASSERT(!HDR_HAS_L2HDR(hdr));
6073 ASSERT(HDR_EMPTY(hdr));
6074
6075 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
6076 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
6077 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
6078
6079 hdr->b_l1hdr.b_arc_access = 0;
6080
6081 /*
6082 * If the buf is being overridden then it may already
6083 * have a hdr that is not empty.
6084 */
6085 buf_discard_identity(hdr);
6086 arc_buf_thaw(buf);
6087
6088 return;
6089 }
6090
6091 kmutex_t *hash_lock = HDR_LOCK(hdr);
6092 mutex_enter(hash_lock);
6093
6094 /*
6095 * This assignment is only valid as long as the hash_lock is
6096 * held, we must be careful not to reference state or the
6097 * b_state field after dropping the lock.
6098 */
6099 arc_state_t *state = hdr->b_l1hdr.b_state;
6100 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
6101 ASSERT3P(state, !=, arc_anon);
6102
6103 /* this buffer is not on any list */
6104 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
6105
6106 if (HDR_HAS_L2HDR(hdr)) {
6107 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
6108
6109 /*
6110 * We have to recheck this conditional again now that
6111 * we're holding the l2ad_mtx to prevent a race with
6112 * another thread which might be concurrently calling
6113 * l2arc_evict(). In that case, l2arc_evict() might have
6114 * destroyed the header's L2 portion as we were waiting
6115 * to acquire the l2ad_mtx.
6116 */
6117 if (HDR_HAS_L2HDR(hdr))
6118 arc_hdr_l2hdr_destroy(hdr);
6119
6120 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
6121 }
6122
6123 /*
6124 * Do we have more than one buf?
6125 */
6126 if (hdr->b_l1hdr.b_bufcnt > 1) {
6127 arc_buf_hdr_t *nhdr;
6128 uint64_t spa = hdr->b_spa;
6129 uint64_t psize = HDR_GET_PSIZE(hdr);
6130 uint64_t lsize = HDR_GET_LSIZE(hdr);
6131 enum zio_compress compress = HDR_GET_COMPRESS(hdr);
6132 arc_buf_contents_t type = arc_buf_type(hdr);
6133 VERIFY3U(hdr->b_type, ==, type);
6134
6135 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
6136 (void) remove_reference(hdr, hash_lock, tag);
6137
6138 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
6139 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
6140 ASSERT(ARC_BUF_LAST(buf));
6141 }
6142
6143 /*
6144 * Pull the data off of this hdr and attach it to
6145 * a new anonymous hdr. Also find the last buffer
6146 * in the hdr's buffer list.
6147 */
6148 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
6149 ASSERT3P(lastbuf, !=, NULL);
6150
6151 /*
6152 * If the current arc_buf_t and the hdr are sharing their data
6153 * buffer, then we must stop sharing that block.
6154 */
6155 if (arc_buf_is_shared(buf)) {
6156 VERIFY(!arc_buf_is_shared(lastbuf));
6157
6158 /*
6159 * First, sever the block sharing relationship between
6160 * buf and the arc_buf_hdr_t.
6161 */
6162 arc_unshare_buf(hdr, buf);
6163
6164 /*
6165 * Now we need to recreate the hdr's b_pabd. Since we
6166 * have lastbuf handy, we try to share with it, but if
6167 * we can't then we allocate a new b_pabd and copy the
6168 * data from buf into it.
6169 */
6170 if (arc_can_share(hdr, lastbuf)) {
6171 arc_share_buf(hdr, lastbuf);
6172 } else {
6173 arc_hdr_alloc_pabd(hdr);
6174 abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
6175 buf->b_data, psize);
6176 }
6177 VERIFY3P(lastbuf->b_data, !=, NULL);
6178 } else if (HDR_SHARED_DATA(hdr)) {
6179 /*
6180 * Uncompressed shared buffers are always at the end
6181 * of the list. Compressed buffers don't have the
6182 * same requirements. This makes it hard to
6183 * simply assert that the lastbuf is shared so
6184 * we rely on the hdr's compression flags to determine
6185 * if we have a compressed, shared buffer.
6186 */
6187 ASSERT(arc_buf_is_shared(lastbuf) ||
6188 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
6189 ASSERT(!ARC_BUF_SHARED(buf));
6190 }
6191 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
6192 ASSERT3P(state, !=, arc_l2c_only);
6193
6194 (void) refcount_remove_many(&state->arcs_size,
6195 arc_buf_size(buf), buf);
6196
6197 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
6198 ASSERT3P(state, !=, arc_l2c_only);
6199 (void) refcount_remove_many(&state->arcs_esize[type],
6200 arc_buf_size(buf), buf);
6201 }
6202
6203 hdr->b_l1hdr.b_bufcnt -= 1;
6204 arc_cksum_verify(buf);
6205 arc_buf_unwatch(buf);
6206
6207 mutex_exit(hash_lock);
6208
6209 /*
6210 * Allocate a new hdr. The new hdr will contain a b_pabd
6211 * buffer which will be freed in arc_write().
6212 */
6213 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type);
6214 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
6215 ASSERT0(nhdr->b_l1hdr.b_bufcnt);
6216 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt));
6217 VERIFY3U(nhdr->b_type, ==, type);
6218 ASSERT(!HDR_SHARED_DATA(nhdr));
6219
6220 nhdr->b_l1hdr.b_buf = buf;
6221 nhdr->b_l1hdr.b_bufcnt = 1;
6222 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
6223 nhdr->b_l1hdr.b_krrp = 0;
6224
6225 buf->b_hdr = nhdr;
6226
6227 mutex_exit(&buf->b_evict_lock);
6228 (void) refcount_add_many(&arc_anon->arcs_size,
6229 arc_buf_size(buf), buf);
6230 } else {
6231 mutex_exit(&buf->b_evict_lock);
6232 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
6233 /* protected by hash lock, or hdr is on arc_anon */
6234 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
6235 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6236 arc_change_state(arc_anon, hdr, hash_lock);
6237 hdr->b_l1hdr.b_arc_access = 0;
6238 mutex_exit(hash_lock);
6239
6240 buf_discard_identity(hdr);
6241 arc_buf_thaw(buf);
6242 }
6243 }
6244
6245 int
6246 arc_released(arc_buf_t *buf)
6247 {
6248 int released;
6249
6250 mutex_enter(&buf->b_evict_lock);
6251 released = (buf->b_data != NULL &&
6252 buf->b_hdr->b_l1hdr.b_state == arc_anon);
6253 mutex_exit(&buf->b_evict_lock);
6254 return (released);
6255 }
6256
6257 #ifdef ZFS_DEBUG
6258 int
6259 arc_referenced(arc_buf_t *buf)
6260 {
6261 int referenced;
6262
6263 mutex_enter(&buf->b_evict_lock);
6264 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
6265 mutex_exit(&buf->b_evict_lock);
6266 return (referenced);
6267 }
6268 #endif
6269
6270 static void
6271 arc_write_ready(zio_t *zio)
6272 {
6273 arc_write_callback_t *callback = zio->io_private;
6274 arc_buf_t *buf = callback->awcb_buf;
6275 arc_buf_hdr_t *hdr = buf->b_hdr;
6276 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp);
6277
6278 ASSERT(HDR_HAS_L1HDR(hdr));
6279 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
6280 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
6281
6282 /*
6283 * If we're reexecuting this zio because the pool suspended, then
6284 * cleanup any state that was previously set the first time the
6285 * callback was invoked.
6286 */
6287 if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
6288 arc_cksum_free(hdr);
6289 arc_buf_unwatch(buf);
6290 if (hdr->b_l1hdr.b_pabd != NULL) {
6291 if (arc_buf_is_shared(buf)) {
6292 arc_unshare_buf(hdr, buf);
6293 } else {
6294 arc_hdr_free_pabd(hdr);
6295 }
6296 }
6297 }
6298 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6299 ASSERT(!HDR_SHARED_DATA(hdr));
6300 ASSERT(!arc_buf_is_shared(buf));
6301
6302 callback->awcb_ready(zio, buf, callback->awcb_private);
6303
6304 if (HDR_IO_IN_PROGRESS(hdr))
6305 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
6306
6307 arc_cksum_compute(buf);
6308 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6309
6310 enum zio_compress compress;
6311 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
6312 compress = ZIO_COMPRESS_OFF;
6313 } else {
6314 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp));
6315 compress = BP_GET_COMPRESS(zio->io_bp);
6316 }
6317 HDR_SET_PSIZE(hdr, psize);
6318 arc_hdr_set_compress(hdr, compress);
6319
6320
6321 /*
6322 * Fill the hdr with data. If the hdr is compressed, the data we want
6323 * is available from the zio, otherwise we can take it from the buf.
6324 *
6325 * We might be able to share the buf's data with the hdr here. However,
6326 * doing so would cause the ARC to be full of linear ABDs if we write a
6327 * lot of shareable data. As a compromise, we check whether scattered
6328 * ABDs are allowed, and assume that if they are then the user wants
6329 * the ARC to be primarily filled with them regardless of the data being
6330 * written. Therefore, if they're allowed then we allocate one and copy
6331 * the data into it; otherwise, we share the data directly if we can.
6332 */
6333 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) {
6334 arc_hdr_alloc_pabd(hdr);
6335
6336 /*
6337 * Ideally, we would always copy the io_abd into b_pabd, but the
6338 * user may have disabled compressed ARC, thus we must check the
6339 * hdr's compression setting rather than the io_bp's.
6340 */
6341 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
6342 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=,
6343 ZIO_COMPRESS_OFF);
6344 ASSERT3U(psize, >, 0);
6345
6346 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
6347 } else {
6348 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
6349
6350 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
6351 arc_buf_size(buf));
6352 }
6353 } else {
6354 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
6355 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
6356 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
6357
6358 arc_share_buf(hdr, buf);
6359 }
6360
6361 arc_hdr_verify(hdr, zio->io_bp);
6362 }
6363
6364 static void
6365 arc_write_children_ready(zio_t *zio)
6366 {
6367 arc_write_callback_t *callback = zio->io_private;
6368 arc_buf_t *buf = callback->awcb_buf;
6369
6370 callback->awcb_children_ready(zio, buf, callback->awcb_private);
6371 }
6372
6373 /*
6374 * The SPA calls this callback for each physical write that happens on behalf
6375 * of a logical write. See the comment in dbuf_write_physdone() for details.
6376 */
6377 static void
6378 arc_write_physdone(zio_t *zio)
6379 {
6380 arc_write_callback_t *cb = zio->io_private;
6381 if (cb->awcb_physdone != NULL)
6382 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
6383 }
6384
6385 static void
6386 arc_write_done(zio_t *zio)
6387 {
6388 arc_write_callback_t *callback = zio->io_private;
6389 arc_buf_t *buf = callback->awcb_buf;
6390 arc_buf_hdr_t *hdr = buf->b_hdr;
6391
6392 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6393
6394 if (zio->io_error == 0) {
6395 arc_hdr_verify(hdr, zio->io_bp);
6396
6397 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
6398 buf_discard_identity(hdr);
6399 } else {
6400 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
6401 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
6402 }
6403 } else {
6404 ASSERT(HDR_EMPTY(hdr));
6405 }
6406
6407 /*
6408 * If the block to be written was all-zero or compressed enough to be
6409 * embedded in the BP, no write was performed so there will be no
6410 * dva/birth/checksum. The buffer must therefore remain anonymous
6411 * (and uncached).
6412 */
6413 if (!HDR_EMPTY(hdr)) {
6414 arc_buf_hdr_t *exists;
6415 kmutex_t *hash_lock;
6416
6417 ASSERT3U(zio->io_error, ==, 0);
6418
6419 arc_cksum_verify(buf);
6420
6421 exists = buf_hash_insert(hdr, &hash_lock);
6422 if (exists != NULL) {
6423 /*
6424 * This can only happen if we overwrite for
6425 * sync-to-convergence, because we remove
6426 * buffers from the hash table when we arc_free().
6427 */
6428 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
6429 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6430 panic("bad overwrite, hdr=%p exists=%p",
6431 (void *)hdr, (void *)exists);
6432 ASSERT(refcount_is_zero(
6433 &exists->b_l1hdr.b_refcnt));
6434 arc_change_state(arc_anon, exists, hash_lock);
6435 arc_wait_for_krrp(exists);
6436 arc_hdr_destroy(exists);
6437 mutex_exit(hash_lock);
6438 exists = buf_hash_insert(hdr, &hash_lock);
6439 ASSERT3P(exists, ==, NULL);
6440 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
6441 /* nopwrite */
6442 ASSERT(zio->io_prop.zp_nopwrite);
6443 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6444 panic("bad nopwrite, hdr=%p exists=%p",
6445 (void *)hdr, (void *)exists);
6446 } else {
6447 /* Dedup */
6448 ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
6449 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
6450 ASSERT(BP_GET_DEDUP(zio->io_bp));
6451 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
6452 }
6453 }
6454 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6455 /* if it's not anon, we are doing a scrub */
6456 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
6457 arc_access(hdr, hash_lock);
6458 mutex_exit(hash_lock);
6459 } else {
6460 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6461 }
6462
6463 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
6464 callback->awcb_done(zio, buf, callback->awcb_private);
6465
6466 abd_put(zio->io_abd);
6467 kmem_free(callback, sizeof (arc_write_callback_t));
6468 }
6469
6470 zio_t *
6471 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
6472 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready,
6473 arc_done_func_t *children_ready, arc_done_func_t *physdone,
6474 arc_done_func_t *done, void *private, zio_priority_t priority,
6475 int zio_flags, const zbookmark_phys_t *zb,
6476 const zio_smartcomp_info_t *smartcomp)
6477 {
6478 arc_buf_hdr_t *hdr = buf->b_hdr;
6479 arc_write_callback_t *callback;
6480 zio_t *zio;
6481 zio_prop_t localprop = *zp;
6482
6483 ASSERT3P(ready, !=, NULL);
6484 ASSERT3P(done, !=, NULL);
6485 ASSERT(!HDR_IO_ERROR(hdr));
6486 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6487 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6488 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
6489 if (l2arc)
6490 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
6491 if (ARC_BUF_COMPRESSED(buf)) {
6492 /*
6493 * We're writing a pre-compressed buffer. Make the
6494 * compression algorithm requested by the zio_prop_t match
6495 * the pre-compressed buffer's compression algorithm.
6496 */
6497 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
6498
6499 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
6500 zio_flags |= ZIO_FLAG_RAW;
6501 }
6502 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
6503 callback->awcb_ready = ready;
6504 callback->awcb_children_ready = children_ready;
6505 callback->awcb_physdone = physdone;
6506 callback->awcb_done = done;
6507 callback->awcb_private = private;
6508 callback->awcb_buf = buf;
6509
6510 /*
6511 * The hdr's b_pabd is now stale, free it now. A new data block
6512 * will be allocated when the zio pipeline calls arc_write_ready().
6513 */
6514 if (hdr->b_l1hdr.b_pabd != NULL) {
6515 /*
6516 * If the buf is currently sharing the data block with
6517 * the hdr then we need to break that relationship here.
6518 * The hdr will remain with a NULL data pointer and the
6519 * buf will take sole ownership of the block.
6520 */
6521 if (arc_buf_is_shared(buf)) {
6522 arc_unshare_buf(hdr, buf);
6523 } else {
6524 arc_hdr_free_pabd(hdr);
6525 }
6526 VERIFY3P(buf->b_data, !=, NULL);
6527 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
6528 }
6529 ASSERT(!arc_buf_is_shared(buf));
6530 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6531
6532 zio = zio_write(pio, spa, txg, bp,
6533 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
6534 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
6535 (children_ready != NULL) ? arc_write_children_ready : NULL,
6536 arc_write_physdone, arc_write_done, callback,
6537 priority, zio_flags, zb, smartcomp);
6538
6539 return (zio);
6540 }
6541
6542 static int
6543 arc_memory_throttle(uint64_t reserve, uint64_t txg)
6544 {
6545 #ifdef _KERNEL
6546 uint64_t available_memory = ptob(freemem);
6547 static uint64_t page_load = 0;
6548 static uint64_t last_txg = 0;
6549
6550 #if defined(__i386)
6551 available_memory =
6552 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
6553 #endif
6554
6555 if (freemem > physmem * arc_lotsfree_percent / 100)
6556 return (0);
6557
6558 if (txg > last_txg) {
6559 last_txg = txg;
6560 page_load = 0;
6561 }
6562 /*
6563 * If we are in pageout, we know that memory is already tight,
6564 * the arc is already going to be evicting, so we just want to
6565 * continue to let page writes occur as quickly as possible.
6566 */
6567 if (curproc == proc_pageout) {
6568 if (page_load > MAX(ptob(minfree), available_memory) / 4)
6569 return (SET_ERROR(ERESTART));
6570 /* Note: reserve is inflated, so we deflate */
6571 page_load += reserve / 8;
6572 return (0);
6573 } else if (page_load > 0 && arc_reclaim_needed()) {
6574 /* memory is low, delay before restarting */
6575 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
6576 return (SET_ERROR(EAGAIN));
6577 }
6578 page_load = 0;
6579 #endif
6580 return (0);
6581 }
6582
6583 void
6584 arc_tempreserve_clear(uint64_t reserve)
6585 {
6586 atomic_add_64(&arc_tempreserve, -reserve);
6587 ASSERT((int64_t)arc_tempreserve >= 0);
6588 }
6589
6590 int
6591 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
6592 {
6593 int error;
6594 uint64_t anon_size;
6595
6596 if (reserve > arc_c/4 && !arc_no_grow)
6597 arc_c = MIN(arc_c_max, reserve * 4);
6598 if (reserve > arc_c)
6599 return (SET_ERROR(ENOMEM));
6600
6601 /*
6602 * Don't count loaned bufs as in flight dirty data to prevent long
6603 * network delays from blocking transactions that are ready to be
6604 * assigned to a txg.
6605 */
6606
6607 /* assert that it has not wrapped around */
6608 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
6609
6610 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
6611 arc_loaned_bytes), 0);
6612
6613 /*
6614 * Writes will, almost always, require additional memory allocations
6615 * in order to compress/encrypt/etc the data. We therefore need to
6616 * make sure that there is sufficient available memory for this.
6617 */
6618 error = arc_memory_throttle(reserve, txg);
6619 if (error != 0)
6620 return (error);
6621
6622 /*
6623 * Throttle writes when the amount of dirty data in the cache
6624 * gets too large. We try to keep the cache less than half full
6625 * of dirty blocks so that our sync times don't grow too large.
6626 * Note: if two requests come in concurrently, we might let them
6627 * both succeed, when one of them should fail. Not a huge deal.
6628 */
6629 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
6630 anon_size > arc_c / 4) {
6631 DTRACE_PROBE4(arc__tempreserve__space__throttle, uint64_t,
6632 arc_tempreserve, arc_state_t *, arc_anon, uint64_t,
6633 reserve, uint64_t, arc_c);
6634
6635 uint64_t meta_esize =
6636 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6637 uint64_t data_esize =
6638 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6639 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
6640 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
6641 arc_tempreserve >> 10, meta_esize >> 10,
6642 data_esize >> 10, reserve >> 10, arc_c >> 10);
6643 return (SET_ERROR(ERESTART));
6644 }
6645 atomic_add_64(&arc_tempreserve, reserve);
6646 return (0);
6647 }
6648
6649 static void
6650 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
6651 kstat_named_t *evict_data, kstat_named_t *evict_metadata,
6652 kstat_named_t *evict_ddt)
6653 {
6654 size->value.ui64 = refcount_count(&state->arcs_size);
6655 evict_data->value.ui64 =
6656 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
6657 evict_metadata->value.ui64 =
6658 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
6659 evict_ddt->value.ui64 =
6660 refcount_count(&state->arcs_esize[ARC_BUFC_DDT]);
6661 }
6662
6663 static int
6664 arc_kstat_update(kstat_t *ksp, int rw)
6665 {
6666 arc_stats_t *as = ksp->ks_data;
6667
6668 if (rw == KSTAT_WRITE) {
6669 return (EACCES);
6670 } else {
6671 arc_kstat_update_state(arc_anon,
6672 &as->arcstat_anon_size,
6673 &as->arcstat_anon_evictable_data,
6674 &as->arcstat_anon_evictable_metadata,
6675 &as->arcstat_anon_evictable_ddt);
6676 arc_kstat_update_state(arc_mru,
6677 &as->arcstat_mru_size,
6678 &as->arcstat_mru_evictable_data,
6679 &as->arcstat_mru_evictable_metadata,
6680 &as->arcstat_mru_evictable_ddt);
6681 arc_kstat_update_state(arc_mru_ghost,
6682 &as->arcstat_mru_ghost_size,
6683 &as->arcstat_mru_ghost_evictable_data,
6684 &as->arcstat_mru_ghost_evictable_metadata,
6685 &as->arcstat_mru_ghost_evictable_ddt);
6686 arc_kstat_update_state(arc_mfu,
6687 &as->arcstat_mfu_size,
6688 &as->arcstat_mfu_evictable_data,
6689 &as->arcstat_mfu_evictable_metadata,
6690 &as->arcstat_mfu_evictable_ddt);
6691 arc_kstat_update_state(arc_mfu_ghost,
6692 &as->arcstat_mfu_ghost_size,
6693 &as->arcstat_mfu_ghost_evictable_data,
6694 &as->arcstat_mfu_ghost_evictable_metadata,
6695 &as->arcstat_mfu_ghost_evictable_ddt);
6696 }
6697
6698 return (0);
6699 }
6700
6701 /*
6702 * This function *must* return indices evenly distributed between all
6703 * sublists of the multilist. This is needed due to how the ARC eviction
6704 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
6705 * distributed between all sublists and uses this assumption when
6706 * deciding which sublist to evict from and how much to evict from it.
6707 */
6708 unsigned int
6709 arc_state_multilist_index_func(multilist_t *ml, void *obj)
6710 {
6711 arc_buf_hdr_t *hdr = obj;
6712
6713 /*
6714 * We rely on b_dva to generate evenly distributed index
6715 * numbers using buf_hash below. So, as an added precaution,
6716 * let's make sure we never add empty buffers to the arc lists.
6717 */
6718 ASSERT(!HDR_EMPTY(hdr));
6719
6720 /*
6721 * The assumption here, is the hash value for a given
6722 * arc_buf_hdr_t will remain constant throughout it's lifetime
6723 * (i.e. it's b_spa, b_dva, and b_birth fields don't change).
6724 * Thus, we don't need to store the header's sublist index
6725 * on insertion, as this index can be recalculated on removal.
6726 *
6727 * Also, the low order bits of the hash value are thought to be
6728 * distributed evenly. Otherwise, in the case that the multilist
6729 * has a power of two number of sublists, each sublists' usage
6730 * would not be evenly distributed.
6731 */
6732 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
6733 multilist_get_num_sublists(ml));
6734 }
6735
6736 static void
6737 arc_state_init(void)
6738 {
6739 arc_anon = &ARC_anon;
6740 arc_mru = &ARC_mru;
6741 arc_mru_ghost = &ARC_mru_ghost;
6742 arc_mfu = &ARC_mfu;
6743 arc_mfu_ghost = &ARC_mfu_ghost;
6744 arc_l2c_only = &ARC_l2c_only;
6745 arc_buf_contents_t arcs;
6746
6747 for (arcs = ARC_BUFC_DATA; arcs < ARC_BUFC_NUMTYPES; ++arcs) {
6748 arc_mru->arcs_list[arcs] =
6749 multilist_create(sizeof (arc_buf_hdr_t),
6750 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6751 arc_state_multilist_index_func);
6752 arc_mru_ghost->arcs_list[arcs] =
6753 multilist_create(sizeof (arc_buf_hdr_t),
6754 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6755 arc_state_multilist_index_func);
6756 arc_mfu->arcs_list[arcs] =
6757 multilist_create(sizeof (arc_buf_hdr_t),
6758 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6759 arc_state_multilist_index_func);
6760 arc_mfu_ghost->arcs_list[arcs] =
6761 multilist_create(sizeof (arc_buf_hdr_t),
6762 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6763 arc_state_multilist_index_func);
6764 arc_l2c_only->arcs_list[arcs] =
6765 multilist_create(sizeof (arc_buf_hdr_t),
6766 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6767 arc_state_multilist_index_func);
6768
6769 refcount_create(&arc_anon->arcs_esize[arcs]);
6770 refcount_create(&arc_mru->arcs_esize[arcs]);
6771 refcount_create(&arc_mru_ghost->arcs_esize[arcs]);
6772 refcount_create(&arc_mfu->arcs_esize[arcs]);
6773 refcount_create(&arc_mfu_ghost->arcs_esize[arcs]);
6774 refcount_create(&arc_l2c_only->arcs_esize[arcs]);
6775 }
6776
6777 arc_flush_taskq = taskq_create("arc_flush_tq",
6778 max_ncpus, minclsyspri, 1, zfs_flush_ntasks, TASKQ_DYNAMIC);
6779
6780 refcount_create(&arc_anon->arcs_size);
6781 refcount_create(&arc_mru->arcs_size);
6782 refcount_create(&arc_mru_ghost->arcs_size);
6783 refcount_create(&arc_mfu->arcs_size);
6784 refcount_create(&arc_mfu_ghost->arcs_size);
6785 refcount_create(&arc_l2c_only->arcs_size);
6786 }
6787
6788 static void
6789 arc_state_fini(void)
6790 {
6791 arc_buf_contents_t arcs;
6792
6793 refcount_destroy(&arc_anon->arcs_size);
6794 refcount_destroy(&arc_mru->arcs_size);
6795 refcount_destroy(&arc_mru_ghost->arcs_size);
6796 refcount_destroy(&arc_mfu->arcs_size);
6797 refcount_destroy(&arc_mfu_ghost->arcs_size);
6798 refcount_destroy(&arc_l2c_only->arcs_size);
6799
6800 for (arcs = ARC_BUFC_DATA; arcs < ARC_BUFC_NUMTYPES; ++arcs) {
6801 multilist_destroy(arc_mru->arcs_list[arcs]);
6802 multilist_destroy(arc_mru_ghost->arcs_list[arcs]);
6803 multilist_destroy(arc_mfu->arcs_list[arcs]);
6804 multilist_destroy(arc_mfu_ghost->arcs_list[arcs]);
6805 multilist_destroy(arc_l2c_only->arcs_list[arcs]);
6806
6807 refcount_destroy(&arc_anon->arcs_esize[arcs]);
6808 refcount_destroy(&arc_mru->arcs_esize[arcs]);
6809 refcount_destroy(&arc_mru_ghost->arcs_esize[arcs]);
6810 refcount_destroy(&arc_mfu->arcs_esize[arcs]);
6811 refcount_destroy(&arc_mfu_ghost->arcs_esize[arcs]);
6812 refcount_destroy(&arc_l2c_only->arcs_esize[arcs]);
6813 }
6814 }
6815
6816 uint64_t
6817 arc_max_bytes(void)
6818 {
6819 return (arc_c_max);
6820 }
6821
6822 void
6823 arc_init(void)
6824 {
6825 /*
6826 * allmem is "all memory that we could possibly use".
6827 */
6828 #ifdef _KERNEL
6829 uint64_t allmem = ptob(physmem - swapfs_minfree);
6830 #else
6831 uint64_t allmem = (physmem * PAGESIZE) / 2;
6832 #endif
6833
6834 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
6835 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
6836 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
6837
6838 /* Convert seconds to clock ticks */
6839 arc_min_prefetch_lifespan = 1 * hz;
6840
6841 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
6842 arc_c_min = MAX(allmem / 32, 64 << 20);
6843 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
6844 if (allmem >= 1 << 30)
6845 arc_c_max = allmem - (1 << 30);
6846 else
6847 arc_c_max = arc_c_min;
6848 arc_c_max = MAX(allmem * 3 / 4, arc_c_max);
6849
6850 /*
6851 * In userland, there's only the memory pressure that we artificially
6852 * create (see arc_available_memory()). Don't let arc_c get too
6853 * small, because it can cause transactions to be larger than
6854 * arc_c, causing arc_tempreserve_space() to fail.
6855 */
6856 #ifndef _KERNEL
6857 arc_c_min = arc_c_max / 2;
6858 #endif
6859
6860 /*
6861 * Allow the tunables to override our calculations if they are
6862 * reasonable (ie. over 64MB)
6863 */
6864 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) {
6865 arc_c_max = zfs_arc_max;
6866 arc_c_min = MIN(arc_c_min, arc_c_max);
6867 }
6868 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max)
6869 arc_c_min = zfs_arc_min;
6870
6871 arc_c = arc_c_max;
6872 arc_p = (arc_c >> 1);
6873 arc_size = 0;
6874
6875 /* limit ddt meta-data to 1/4 of the arc capacity */
6876 arc_ddt_limit = arc_c_max / 4;
6877 /* limit meta-data to 1/4 of the arc capacity */
6878 arc_meta_limit = arc_c_max / 4;
6879
6880 #ifdef _KERNEL
6881 /*
6882 * Metadata is stored in the kernel's heap. Don't let us
6883 * use more than half the heap for the ARC.
6884 */
6885 arc_meta_limit = MIN(arc_meta_limit,
6886 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2);
6887 #endif
6888
6889 /* Allow the tunable to override if it is reasonable */
6890 if (zfs_arc_ddt_limit > 0 && zfs_arc_ddt_limit <= arc_c_max)
6891 arc_ddt_limit = zfs_arc_ddt_limit;
6892 arc_ddt_evict_threshold =
6893 zfs_arc_segregate_ddt ? &arc_ddt_limit : &arc_meta_limit;
6894
6895 /* Allow the tunable to override if it is reasonable */
6896 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
6897 arc_meta_limit = zfs_arc_meta_limit;
6898
6899 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
6900 arc_c_min = arc_meta_limit / 2;
6901
6902 if (zfs_arc_meta_min > 0) {
6903 arc_meta_min = zfs_arc_meta_min;
6904 } else {
6905 arc_meta_min = arc_c_min / 2;
6906 }
6907
6908 if (zfs_arc_grow_retry > 0)
6909 arc_grow_retry = zfs_arc_grow_retry;
6910
6911 if (zfs_arc_shrink_shift > 0)
6912 arc_shrink_shift = zfs_arc_shrink_shift;
6913
6914 /*
6915 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
6916 */
6917 if (arc_no_grow_shift >= arc_shrink_shift)
6918 arc_no_grow_shift = arc_shrink_shift - 1;
6919
6920 if (zfs_arc_p_min_shift > 0)
6921 arc_p_min_shift = zfs_arc_p_min_shift;
6922
6923 /* if kmem_flags are set, lets try to use less memory */
6924 if (kmem_debugging())
6925 arc_c = arc_c / 2;
6926 if (arc_c < arc_c_min)
6927 arc_c = arc_c_min;
6928
6929 arc_state_init();
6930 buf_init();
6931
6932 arc_reclaim_thread_exit = B_FALSE;
6933
6934 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
6935 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
6936
6937 if (arc_ksp != NULL) {
6938 arc_ksp->ks_data = &arc_stats;
6939 arc_ksp->ks_update = arc_kstat_update;
6940 kstat_install(arc_ksp);
6941 }
6942
6943 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
6944 TS_RUN, minclsyspri);
6945
6946 arc_dead = B_FALSE;
6947 arc_warm = B_FALSE;
6948
6949 /*
6950 * Calculate maximum amount of dirty data per pool.
6951 *
6952 * If it has been set by /etc/system, take that.
6953 * Otherwise, use a percentage of physical memory defined by
6954 * zfs_dirty_data_max_percent (default 10%) with a cap at
6955 * zfs_dirty_data_max_max (default 4GB).
6956 */
6957 if (zfs_dirty_data_max == 0) {
6958 zfs_dirty_data_max = physmem * PAGESIZE *
6959 zfs_dirty_data_max_percent / 100;
6960 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
6961 zfs_dirty_data_max_max);
6962 }
6963 }
6964
6965 void
6966 arc_fini(void)
6967 {
6968 mutex_enter(&arc_reclaim_lock);
6969 arc_reclaim_thread_exit = B_TRUE;
6970 /*
6971 * The reclaim thread will set arc_reclaim_thread_exit back to
6972 * B_FALSE when it is finished exiting; we're waiting for that.
6973 */
6974 while (arc_reclaim_thread_exit) {
6975 cv_signal(&arc_reclaim_thread_cv);
6976 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
6977 }
6978 mutex_exit(&arc_reclaim_lock);
6979
6980 /* Use B_TRUE to ensure *all* buffers are evicted */
6981 arc_flush(NULL, B_TRUE);
6982
6983 arc_dead = B_TRUE;
6984
6985 if (arc_ksp != NULL) {
6986 kstat_delete(arc_ksp);
6987 arc_ksp = NULL;
6988 }
6989
6990 taskq_destroy(arc_flush_taskq);
6991
6992 mutex_destroy(&arc_reclaim_lock);
6993 cv_destroy(&arc_reclaim_thread_cv);
6994 cv_destroy(&arc_reclaim_waiters_cv);
6995
6996 arc_state_fini();
6997 buf_fini();
6998
6999 ASSERT0(arc_loaned_bytes);
7000 }
7001
7002 /*
7003 * Level 2 ARC
7004 *
7005 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
7006 * It uses dedicated storage devices to hold cached data, which are populated
7007 * using large infrequent writes. The main role of this cache is to boost
7008 * the performance of random read workloads. The intended L2ARC devices
7009 * include short-stroked disks, solid state disks, and other media with
7010 * substantially faster read latency than disk.
7011 *
7012 * +-----------------------+
7013 * | ARC |
7014 * +-----------------------+
7015 * | ^ ^
7016 * | | |
7017 * l2arc_feed_thread() arc_read()
7018 * | | |
7019 * | l2arc read |
7020 * V | |
7021 * +---------------+ |
7022 * | L2ARC | |
7023 * +---------------+ |
7024 * | ^ |
7025 * l2arc_write() | |
7026 * | | |
7027 * V | |
7028 * +-------+ +-------+
7029 * | vdev | | vdev |
7030 * | cache | | cache |
7031 * +-------+ +-------+
7032 * +=========+ .-----.
7033 * : L2ARC : |-_____-|
7034 * : devices : | Disks |
7035 * +=========+ `-_____-'
7036 *
7037 * Read requests are satisfied from the following sources, in order:
7038 *
7039 * 1) ARC
7040 * 2) vdev cache of L2ARC devices
7041 * 3) L2ARC devices
7042 * 4) vdev cache of disks
7043 * 5) disks
7044 *
7045 * Some L2ARC device types exhibit extremely slow write performance.
7046 * To accommodate for this there are some significant differences between
7047 * the L2ARC and traditional cache design:
7048 *
7049 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
7050 * the ARC behave as usual, freeing buffers and placing headers on ghost
7051 * lists. The ARC does not send buffers to the L2ARC during eviction as
7052 * this would add inflated write latencies for all ARC memory pressure.
7053 *
7054 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
7055 * It does this by periodically scanning buffers from the eviction-end of
7056 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
7057 * not already there. It scans until a headroom of buffers is satisfied,
7058 * which itself is a buffer for ARC eviction. If a compressible buffer is
7059 * found during scanning and selected for writing to an L2ARC device, we
7060 * temporarily boost scanning headroom during the next scan cycle to make
7061 * sure we adapt to compression effects (which might significantly reduce
7062 * the data volume we write to L2ARC). The thread that does this is
7063 * l2arc_feed_thread(), illustrated below; example sizes are included to
7064 * provide a better sense of ratio than this diagram:
7065 *
7066 * head --> tail
7067 * +---------------------+----------+
7068 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
7069 * +---------------------+----------+ | o L2ARC eligible
7070 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
7071 * +---------------------+----------+ |
7072 * 15.9 Gbytes ^ 32 Mbytes |
7073 * headroom |
7074 * l2arc_feed_thread()
7075 * |
7076 * l2arc write hand <--[oooo]--'
7077 * | 8 Mbyte
7078 * | write max
7079 * V
7080 * +==============================+
7081 * L2ARC dev |####|#|###|###| |####| ... |
7082 * +==============================+
7083 * 32 Gbytes
7084 *
7085 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
7086 * evicted, then the L2ARC has cached a buffer much sooner than it probably
7087 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
7088 * safe to say that this is an uncommon case, since buffers at the end of
7089 * the ARC lists have moved there due to inactivity.
7090 *
7091 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
7092 * then the L2ARC simply misses copying some buffers. This serves as a
7093 * pressure valve to prevent heavy read workloads from both stalling the ARC
7094 * with waits and clogging the L2ARC with writes. This also helps prevent
7095 * the potential for the L2ARC to churn if it attempts to cache content too
7096 * quickly, such as during backups of the entire pool.
7097 *
7098 * 5. After system boot and before the ARC has filled main memory, there are
7099 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
7100 * lists can remain mostly static. Instead of searching from tail of these
7101 * lists as pictured, the l2arc_feed_thread() will search from the list heads
7102 * for eligible buffers, greatly increasing its chance of finding them.
7103 *
7104 * The L2ARC device write speed is also boosted during this time so that
7105 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
7106 * there are no L2ARC reads, and no fear of degrading read performance
7107 * through increased writes.
7108 *
7109 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
7110 * the vdev queue can aggregate them into larger and fewer writes. Each
7111 * device is written to in a rotor fashion, sweeping writes through
7112 * available space then repeating.
7113 *
7114 * 7. The L2ARC does not store dirty content. It never needs to flush
7115 * write buffers back to disk based storage.
7116 *
7117 * 8. If an ARC buffer is written (and dirtied) which also exists in the
7118 * L2ARC, the now stale L2ARC buffer is immediately dropped.
7119 *
7120 * The performance of the L2ARC can be tweaked by a number of tunables, which
7121 * may be necessary for different workloads:
7122 *
7123 * l2arc_write_max max write bytes per interval
7124 * l2arc_write_boost extra write bytes during device warmup
7125 * l2arc_noprefetch skip caching prefetched buffers
7126 * l2arc_headroom number of max device writes to precache
7127 * l2arc_headroom_boost when we find compressed buffers during ARC
7128 * scanning, we multiply headroom by this
7129 * percentage factor for the next scan cycle,
7130 * since more compressed buffers are likely to
7131 * be present
7132 * l2arc_feed_secs seconds between L2ARC writing
7133 *
7134 * Tunables may be removed or added as future performance improvements are
7135 * integrated, and also may become zpool properties.
7136 *
7137 * There are three key functions that control how the L2ARC warms up:
7138 *
7139 * l2arc_write_eligible() check if a buffer is eligible to cache
7140 * l2arc_write_size() calculate how much to write
7141 * l2arc_write_interval() calculate sleep delay between writes
7142 *
7143 * These three functions determine what to write, how much, and how quickly
7144 * to send writes.
7145 *
7146 * L2ARC persistency:
7147 *
7148 * When writing buffers to L2ARC, we periodically add some metadata to
7149 * make sure we can pick them up after reboot, thus dramatically reducing
7150 * the impact that any downtime has on the performance of storage systems
7151 * with large caches.
7152 *
7153 * The implementation works fairly simply by integrating the following two
7154 * modifications:
7155 *
7156 * *) Every now and then we mix in a piece of metadata (called a log block)
7157 * into the L2ARC write. This allows us to understand what's been written,
7158 * so that we can rebuild the arc_buf_hdr_t structures of the main ARC
7159 * buffers. The log block also includes a "2-back-reference" pointer to
7160 * he second-to-previous block, forming a back-linked list of blocks on
7161 * the L2ARC device.
7162 *
7163 * *) We reserve SPA_MINBLOCKSIZE of space at the start of each L2ARC device
7164 * for our header bookkeeping purposes. This contains a device header,
7165 * which contains our top-level reference structures. We update it each
7166 * time we write a new log block, so that we're able to locate it in the
7167 * L2ARC device. If this write results in an inconsistent device header
7168 * (e.g. due to power failure), we detect this by verifying the header's
7169 * checksum and simply drop the entries from L2ARC.
7170 *
7171 * Implementation diagram:
7172 *
7173 * +=== L2ARC device (not to scale) ======================================+
7174 * | ___two newest log block pointers__.__________ |
7175 * | / \1 back \latest |
7176 * |.____/_. V V |
7177 * ||L2 dev|....|lb |bufs |lb |bufs |lb |bufs |lb |bufs |lb |---(empty)---|
7178 * || hdr| ^ /^ /^ / / |
7179 * |+------+ ...--\-------/ \-----/--\------/ / |
7180 * | \--------------/ \--------------/ |
7181 * +======================================================================+
7182 *
7183 * As can be seen on the diagram, rather than using a simple linked list,
7184 * we use a pair of linked lists with alternating elements. This is a
7185 * performance enhancement due to the fact that we only find out of the
7186 * address of the next log block access once the current block has been
7187 * completely read in. Obviously, this hurts performance, because we'd be
7188 * keeping the device's I/O queue at only a 1 operation deep, thus
7189 * incurring a large amount of I/O round-trip latency. Having two lists
7190 * allows us to "prefetch" two log blocks ahead of where we are currently
7191 * rebuilding L2ARC buffers.
7192 *
7193 * On-device data structures:
7194 *
7195 * L2ARC device header: l2arc_dev_hdr_phys_t
7196 * L2ARC log block: l2arc_log_blk_phys_t
7197 *
7198 * L2ARC reconstruction:
7199 *
7200 * When writing data, we simply write in the standard rotary fashion,
7201 * evicting buffers as we go and simply writing new data over them (writing
7202 * a new log block every now and then). This obviously means that once we
7203 * loop around the end of the device, we will start cutting into an already
7204 * committed log block (and its referenced data buffers), like so:
7205 *
7206 * current write head__ __old tail
7207 * \ /
7208 * V V
7209 * <--|bufs |lb |bufs |lb | |bufs |lb |bufs |lb |-->
7210 * ^ ^^^^^^^^^___________________________________
7211 * | \
7212 * <<nextwrite>> may overwrite this blk and/or its bufs --'
7213 *
7214 * When importing the pool, we detect this situation and use it to stop
7215 * our scanning process (see l2arc_rebuild).
7216 *
7217 * There is one significant caveat to consider when rebuilding ARC contents
7218 * from an L2ARC device: what about invalidated buffers? Given the above
7219 * construction, we cannot update blocks which we've already written to amend
7220 * them to remove buffers which were invalidated. Thus, during reconstruction,
7221 * we might be populating the cache with buffers for data that's not on the
7222 * main pool anymore, or may have been overwritten!
7223 *
7224 * As it turns out, this isn't a problem. Every arc_read request includes
7225 * both the DVA and, crucially, the birth TXG of the BP the caller is
7226 * looking for. So even if the cache were populated by completely rotten
7227 * blocks for data that had been long deleted and/or overwritten, we'll
7228 * never actually return bad data from the cache, since the DVA with the
7229 * birth TXG uniquely identify a block in space and time - once created,
7230 * a block is immutable on disk. The worst thing we have done is wasted
7231 * some time and memory at l2arc rebuild to reconstruct outdated ARC
7232 * entries that will get dropped from the l2arc as it is being updated
7233 * with new blocks.
7234 */
7235
7236 static boolean_t
7237 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
7238 {
7239 /*
7240 * A buffer is *not* eligible for the L2ARC if it:
7241 * 1. belongs to a different spa.
7242 * 2. is already cached on the L2ARC.
7243 * 3. has an I/O in progress (it may be an incomplete read).
7244 * 4. is flagged not eligible (zfs property).
7245 */
7246 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
7247 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr))
7248 return (B_FALSE);
7249
7250 return (B_TRUE);
7251 }
7252
7253 static uint64_t
7254 l2arc_write_size(void)
7255 {
7256 uint64_t size;
7257
7258 /*
7259 * Make sure our globals have meaningful values in case the user
7260 * altered them.
7261 */
7262 size = l2arc_write_max;
7263 if (size == 0) {
7264 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
7265 "be greater than zero, resetting it to the default (%d)",
7266 L2ARC_WRITE_SIZE);
7267 size = l2arc_write_max = L2ARC_WRITE_SIZE;
7268 }
7269
7270 if (arc_warm == B_FALSE)
7271 size += l2arc_write_boost;
7272
7273 return (size);
7274
7275 }
7276
7277 static clock_t
7278 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
7279 {
7280 clock_t interval, next, now;
7281
7282 /*
7283 * If the ARC lists are busy, increase our write rate; if the
7284 * lists are stale, idle back. This is achieved by checking
7285 * how much we previously wrote - if it was more than half of
7286 * what we wanted, schedule the next write much sooner.
7287 */
7288 if (l2arc_feed_again && wrote > (wanted / 2))
7289 interval = (hz * l2arc_feed_min_ms) / 1000;
7290 else
7291 interval = hz * l2arc_feed_secs;
7292
7293 now = ddi_get_lbolt();
7294 next = MAX(now, MIN(now + interval, began + interval));
7295
7296 return (next);
7297 }
7298
7299 typedef enum l2ad_feed {
7300 L2ARC_FEED_ALL = 1,
7301 L2ARC_FEED_DDT_DEV,
7302 L2ARC_FEED_NON_DDT_DEV,
7303 } l2ad_feed_t;
7304
7305 /*
7306 * Cycle through L2ARC devices. This is how L2ARC load balances.
7307 * If a device is returned, this also returns holding the spa config lock.
7308 */
7309 static l2arc_dev_t *
7310 l2arc_dev_get_next(l2ad_feed_t feed_type)
7311 {
7312 l2arc_dev_t *start = NULL, *next = NULL;
7313
7314 /*
7315 * Lock out the removal of spas (spa_namespace_lock), then removal
7316 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
7317 * both locks will be dropped and a spa config lock held instead.
7318 */
7319 mutex_enter(&spa_namespace_lock);
7320 mutex_enter(&l2arc_dev_mtx);
7321
7322 /* if there are no vdevs, there is nothing to do */
7323 if (l2arc_ndev == 0)
7324 goto out;
7325
7326 if (feed_type == L2ARC_FEED_DDT_DEV)
7327 next = l2arc_ddt_dev_last;
7328 else
7329 next = l2arc_dev_last;
7330
7331 /* figure out what the next device we look at should be */
7332 if (next == NULL)
7333 next = list_head(l2arc_dev_list);
7334 else if (list_next(l2arc_dev_list, next) == NULL)
7335 next = list_head(l2arc_dev_list);
7336 else
7337 next = list_next(l2arc_dev_list, next);
7338 ASSERT(next);
7339
7340 /* loop through L2ARC devs looking for the one we need */
7341 /* LINTED(E_CONSTANT_CONDITION) */
7342 while (1) {
7343 if (next == NULL) /* reached list end, start from beginning */
7344 next = list_head(l2arc_dev_list);
7345
7346 if (start == NULL) { /* save starting dev */
7347 start = next;
7348 } else if (start == next) { /* full loop completed - stop now */
7349 next = NULL;
7350 if (feed_type == L2ARC_FEED_DDT_DEV) {
7351 l2arc_ddt_dev_last = NULL;
7352 goto out;
7353 } else {
7354 break;
7355 }
7356 }
7357
7358 if (!vdev_is_dead(next->l2ad_vdev) && !next->l2ad_rebuild) {
7359 if (feed_type == L2ARC_FEED_DDT_DEV) {
7360 if (vdev_type_is_ddt(next->l2ad_vdev)) {
7361 l2arc_ddt_dev_last = next;
7362 goto out;
7363 }
7364 } else if (feed_type == L2ARC_FEED_NON_DDT_DEV) {
7365 if (!vdev_type_is_ddt(next->l2ad_vdev)) {
7366 break;
7367 }
7368 } else {
7369 ASSERT(feed_type == L2ARC_FEED_ALL);
7370 break;
7371 }
7372 }
7373 next = list_next(l2arc_dev_list, next);
7374 }
7375 l2arc_dev_last = next;
7376
7377 out:
7378 mutex_exit(&l2arc_dev_mtx);
7379
7380 /*
7381 * Grab the config lock to prevent the 'next' device from being
7382 * removed while we are writing to it.
7383 */
7384 if (next != NULL)
7385 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
7386 mutex_exit(&spa_namespace_lock);
7387
7388 return (next);
7389 }
7390
7391 /*
7392 * Free buffers that were tagged for destruction.
7393 */
7394 static void
7395 l2arc_do_free_on_write()
7396 {
7397 list_t *buflist;
7398 l2arc_data_free_t *df, *df_prev;
7399
7400 mutex_enter(&l2arc_free_on_write_mtx);
7401 buflist = l2arc_free_on_write;
7402
7403 for (df = list_tail(buflist); df; df = df_prev) {
7404 df_prev = list_prev(buflist, df);
7405 ASSERT3P(df->l2df_abd, !=, NULL);
7406 abd_free(df->l2df_abd);
7407 list_remove(buflist, df);
7408 kmem_free(df, sizeof (l2arc_data_free_t));
7409 }
7410
7411 mutex_exit(&l2arc_free_on_write_mtx);
7412 }
7413
7414 /*
7415 * A write to a cache device has completed. Update all headers to allow
7416 * reads from these buffers to begin.
7417 */
7418 static void
7419 l2arc_write_done(zio_t *zio)
7420 {
7421 l2arc_write_callback_t *cb;
7422 l2arc_dev_t *dev;
7423 list_t *buflist;
7424 arc_buf_hdr_t *head, *hdr, *hdr_prev;
7425 kmutex_t *hash_lock;
7426 int64_t bytes_dropped = 0;
7427 l2arc_log_blk_buf_t *lb_buf;
7428
7429 cb = zio->io_private;
7430 ASSERT3P(cb, !=, NULL);
7431 dev = cb->l2wcb_dev;
7432 ASSERT3P(dev, !=, NULL);
7433 head = cb->l2wcb_head;
7434 ASSERT3P(head, !=, NULL);
7435 buflist = &dev->l2ad_buflist;
7436 ASSERT3P(buflist, !=, NULL);
7437 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
7438 l2arc_write_callback_t *, cb);
7439
7440 if (zio->io_error != 0)
7441 ARCSTAT_BUMP(arcstat_l2_writes_error);
7442
7443 /*
7444 * All writes completed, or an error was hit.
7445 */
7446 top:
7447 mutex_enter(&dev->l2ad_mtx);
7448 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
7449 hdr_prev = list_prev(buflist, hdr);
7450
7451 hash_lock = HDR_LOCK(hdr);
7452
7453 /*
7454 * We cannot use mutex_enter or else we can deadlock
7455 * with l2arc_write_buffers (due to swapping the order
7456 * the hash lock and l2ad_mtx are taken).
7457 */
7458 if (!mutex_tryenter(hash_lock)) {
7459 /*
7460 * Missed the hash lock. We must retry so we
7461 * don't leave the ARC_FLAG_L2_WRITING bit set.
7462 */
7463 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
7464
7465 /*
7466 * We don't want to rescan the headers we've
7467 * already marked as having been written out, so
7468 * we reinsert the head node so we can pick up
7469 * where we left off.
7470 */
7471 list_remove(buflist, head);
7472 list_insert_after(buflist, hdr, head);
7473
7474 mutex_exit(&dev->l2ad_mtx);
7475
7476 /*
7477 * We wait for the hash lock to become available
7478 * to try and prevent busy waiting, and increase
7479 * the chance we'll be able to acquire the lock
7480 * the next time around.
7481 */
7482 mutex_enter(hash_lock);
7483 mutex_exit(hash_lock);
7484 goto top;
7485 }
7486
7487 /*
7488 * We could not have been moved into the arc_l2c_only
7489 * state while in-flight due to our ARC_FLAG_L2_WRITING
7490 * bit being set. Let's just ensure that's being enforced.
7491 */
7492 ASSERT(HDR_HAS_L1HDR(hdr));
7493
7494 if (zio->io_error != 0) {
7495 /*
7496 * Error - drop L2ARC entry.
7497 */
7498 list_remove(buflist, hdr);
7499 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
7500
7501 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr));
7502 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
7503
7504 bytes_dropped += arc_hdr_size(hdr);
7505 (void) refcount_remove_many(&dev->l2ad_alloc,
7506 arc_hdr_size(hdr), hdr);
7507 }
7508
7509 /*
7510 * Allow ARC to begin reads and ghost list evictions to
7511 * this L2ARC entry.
7512 */
7513 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
7514
7515 mutex_exit(hash_lock);
7516 }
7517
7518 atomic_inc_64(&l2arc_writes_done);
7519 list_remove(buflist, head);
7520 ASSERT(!HDR_HAS_L1HDR(head));
7521 kmem_cache_free(hdr_l2only_cache, head);
7522 mutex_exit(&dev->l2ad_mtx);
7523
7524 ASSERT(dev->l2ad_vdev != NULL);
7525 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
7526
7527 l2arc_do_free_on_write();
7528
7529 while ((lb_buf = list_remove_tail(&cb->l2wcb_log_blk_buflist)) != NULL)
7530 kmem_free(lb_buf, sizeof (*lb_buf));
7531 list_destroy(&cb->l2wcb_log_blk_buflist);
7532 kmem_free(cb, sizeof (l2arc_write_callback_t));
7533 }
7534
7535 /*
7536 * A read to a cache device completed. Validate buffer contents before
7537 * handing over to the regular ARC routines.
7538 */
7539 static void
7540 l2arc_read_done(zio_t *zio)
7541 {
7542 l2arc_read_callback_t *cb;
7543 arc_buf_hdr_t *hdr;
7544 kmutex_t *hash_lock;
7545 boolean_t valid_cksum;
7546
7547 ASSERT3P(zio->io_vd, !=, NULL);
7548 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
7549
7550 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
7551
7552 cb = zio->io_private;
7553 ASSERT3P(cb, !=, NULL);
7554 hdr = cb->l2rcb_hdr;
7555 ASSERT3P(hdr, !=, NULL);
7556
7557 hash_lock = HDR_LOCK(hdr);
7558 mutex_enter(hash_lock);
7559 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
7560
7561 /*
7562 * If the data was read into a temporary buffer,
7563 * move it and free the buffer.
7564 */
7565 if (cb->l2rcb_abd != NULL) {
7566 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
7567 if (zio->io_error == 0) {
7568 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd,
7569 arc_hdr_size(hdr));
7570 }
7571
7572 /*
7573 * The following must be done regardless of whether
7574 * there was an error:
7575 * - free the temporary buffer
7576 * - point zio to the real ARC buffer
7577 * - set zio size accordingly
7578 * These are required because zio is either re-used for
7579 * an I/O of the block in the case of the error
7580 * or the zio is passed to arc_read_done() and it
7581 * needs real data.
7582 */
7583 abd_free(cb->l2rcb_abd);
7584 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
7585 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
7586 }
7587
7588 ASSERT3P(zio->io_abd, !=, NULL);
7589
7590 /*
7591 * Check this survived the L2ARC journey.
7592 */
7593 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd);
7594 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
7595 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
7596
7597 valid_cksum = arc_cksum_is_equal(hdr, zio);
7598 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
7599 mutex_exit(hash_lock);
7600 zio->io_private = hdr;
7601 arc_read_done(zio);
7602 } else {
7603 mutex_exit(hash_lock);
7604 /*
7605 * Buffer didn't survive caching. Increment stats and
7606 * reissue to the original storage device.
7607 */
7608 if (zio->io_error != 0) {
7609 ARCSTAT_BUMP(arcstat_l2_io_error);
7610 } else {
7611 zio->io_error = SET_ERROR(EIO);
7612 }
7613 if (!valid_cksum)
7614 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
7615
7616 /*
7617 * If there's no waiter, issue an async i/o to the primary
7618 * storage now. If there *is* a waiter, the caller must
7619 * issue the i/o in a context where it's OK to block.
7620 */
7621 if (zio->io_waiter == NULL) {
7622 zio_t *pio = zio_unique_parent(zio);
7623
7624 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
7625
7626 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp,
7627 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done,
7628 hdr, zio->io_priority, cb->l2rcb_flags,
7629 &cb->l2rcb_zb));
7630 }
7631 }
7632
7633 kmem_free(cb, sizeof (l2arc_read_callback_t));
7634 }
7635
7636 /*
7637 * This is the list priority from which the L2ARC will search for pages to
7638 * cache. This is used within loops to cycle through lists in the
7639 * desired order. This order can have a significant effect on cache
7640 * performance.
7641 *
7642 * Currently the ddt lists are hit first (MFU then MRU),
7643 * followed by metadata then by the data lists.
7644 * This function returns a locked list, and also returns the lock pointer.
7645 */
7646 static multilist_sublist_t *
7647 l2arc_sublist_lock(enum l2arc_priorities prio)
7648 {
7649 multilist_t *ml = NULL;
7650 unsigned int idx;
7651
7652 ASSERT(prio >= PRIORITY_MFU_DDT);
7653 ASSERT(prio < PRIORITY_NUMTYPES);
7654
7655 switch (prio) {
7656 case PRIORITY_MFU_DDT:
7657 ml = arc_mfu->arcs_list[ARC_BUFC_DDT];
7658 break;
7659 case PRIORITY_MRU_DDT:
7660 ml = arc_mru->arcs_list[ARC_BUFC_DDT];
7661 break;
7662 case PRIORITY_MFU_META:
7663 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
7664 break;
7665 case PRIORITY_MRU_META:
7666 ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
7667 break;
7668 case PRIORITY_MFU_DATA:
7669 ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
7670 break;
7671 case PRIORITY_MRU_DATA:
7672 ml = arc_mru->arcs_list[ARC_BUFC_DATA];
7673 break;
7674 }
7675
7676 /*
7677 * Return a randomly-selected sublist. This is acceptable
7678 * because the caller feeds only a little bit of data for each
7679 * call (8MB). Subsequent calls will result in different
7680 * sublists being selected.
7681 */
7682 idx = multilist_get_random_index(ml);
7683 return (multilist_sublist_lock(ml, idx));
7684 }
7685
7686 /*
7687 * Calculates the maximum overhead of L2ARC metadata log blocks for a given
7688 * L2ARC write size. l2arc_evict and l2arc_write_buffers need to include this
7689 * overhead in processing to make sure there is enough headroom available
7690 * when writing buffers.
7691 */
7692 static inline uint64_t
7693 l2arc_log_blk_overhead(uint64_t write_sz)
7694 {
7695 return ((write_sz / SPA_MINBLOCKSIZE / L2ARC_LOG_BLK_ENTRIES) + 1) *
7696 L2ARC_LOG_BLK_SIZE;
7697 }
7698
7699 /*
7700 * Evict buffers from the device write hand to the distance specified in
7701 * bytes. This distance may span populated buffers, it may span nothing.
7702 * This is clearing a region on the L2ARC device ready for writing.
7703 * If the 'all' boolean is set, every buffer is evicted.
7704 */
7705 static void
7706 l2arc_evict_impl(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
7707 {
7708 list_t *buflist;
7709 arc_buf_hdr_t *hdr, *hdr_prev;
7710 kmutex_t *hash_lock;
7711 uint64_t taddr;
7712
7713 buflist = &dev->l2ad_buflist;
7714
7715 if (!all && dev->l2ad_first) {
7716 /*
7717 * This is the first sweep through the device. There is
7718 * nothing to evict.
7719 */
7720 return;
7721 }
7722
7723 /*
7724 * We need to add in the worst case scenario of log block overhead.
7725 */
7726 distance += l2arc_log_blk_overhead(distance);
7727 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
7728 /*
7729 * When nearing the end of the device, evict to the end
7730 * before the device write hand jumps to the start.
7731 */
7732 taddr = dev->l2ad_end;
7733 } else {
7734 taddr = dev->l2ad_hand + distance;
7735 }
7736 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
7737 uint64_t, taddr, boolean_t, all);
7738
7739 top:
7740 mutex_enter(&dev->l2ad_mtx);
7741 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
7742 hdr_prev = list_prev(buflist, hdr);
7743
7744 hash_lock = HDR_LOCK(hdr);
7745
7746 /*
7747 * We cannot use mutex_enter or else we can deadlock
7748 * with l2arc_write_buffers (due to swapping the order
7749 * the hash lock and l2ad_mtx are taken).
7750 */
7751 if (!mutex_tryenter(hash_lock)) {
7752 /*
7753 * Missed the hash lock. Retry.
7754 */
7755 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
7756 mutex_exit(&dev->l2ad_mtx);
7757 mutex_enter(hash_lock);
7758 mutex_exit(hash_lock);
7759 goto top;
7760 }
7761
7762 /*
7763 * A header can't be on this list if it doesn't have L2 header.
7764 */
7765 ASSERT(HDR_HAS_L2HDR(hdr));
7766
7767 /* Ensure this header has finished being written. */
7768 ASSERT(!HDR_L2_WRITING(hdr));
7769 ASSERT(!HDR_L2_WRITE_HEAD(hdr));
7770
7771 if (!all && (hdr->b_l2hdr.b_daddr >= taddr ||
7772 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
7773 /*
7774 * We've evicted to the target address,
7775 * or the end of the device.
7776 */
7777 mutex_exit(hash_lock);
7778 break;
7779 }
7780
7781 if (!HDR_HAS_L1HDR(hdr)) {
7782 ASSERT(!HDR_L2_READING(hdr));
7783 /*
7784 * This doesn't exist in the ARC. Destroy.
7785 * arc_hdr_destroy() will call list_remove()
7786 * and decrement arcstat_l2_lsize.
7787 */
7788 arc_change_state(arc_anon, hdr, hash_lock);
7789 arc_hdr_destroy(hdr);
7790 } else {
7791 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
7792 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
7793 /*
7794 * Invalidate issued or about to be issued
7795 * reads, since we may be about to write
7796 * over this location.
7797 */
7798 if (HDR_L2_READING(hdr)) {
7799 ARCSTAT_BUMP(arcstat_l2_evict_reading);
7800 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
7801 }
7802
7803 arc_hdr_l2hdr_destroy(hdr);
7804 }
7805 mutex_exit(hash_lock);
7806 }
7807 mutex_exit(&dev->l2ad_mtx);
7808 }
7809
7810 static void
7811 l2arc_evict_task(void *arg)
7812 {
7813 l2arc_dev_t *dev = arg;
7814 ASSERT(dev);
7815
7816 /*
7817 * Evict l2arc buffers asynchronously; we need to keep the device
7818 * around until we are sure there aren't any buffers referencing it.
7819 * We do not need to hold any config locks, etc. because at this point,
7820 * we are the only ones who knows about this device (the in-core
7821 * structure), so no new buffers can be created (e.g. if the pool is
7822 * re-imported while the asynchronous eviction is in progress) that
7823 * reference this same in-core structure. Also remove the vdev link
7824 * since further use of it as l2arc device is prohibited.
7825 */
7826 dev->l2ad_vdev = NULL;
7827 l2arc_evict_impl(dev, 0LL, B_TRUE);
7828
7829 /* Same cleanup as in the synchronous path */
7830 list_destroy(&dev->l2ad_buflist);
7831 mutex_destroy(&dev->l2ad_mtx);
7832 refcount_destroy(&dev->l2ad_alloc);
7833 kmem_free(dev->l2ad_dev_hdr, dev->l2ad_dev_hdr_asize);
7834 kmem_free(dev, sizeof (l2arc_dev_t));
7835 }
7836
7837 boolean_t zfs_l2arc_async_evict = B_TRUE;
7838
7839 /*
7840 * Perform l2arc eviction for buffers associated with this device
7841 * If evicting all buffers (done at pool export time), try to evict
7842 * asynchronously, and fall back to synchronous eviction in case of error
7843 * Tell the caller whether to cleanup the device:
7844 * - B_TRUE means "asynchronous eviction, do not cleanup"
7845 * - B_FALSE means "synchronous eviction, done, please cleanup"
7846 */
7847 static boolean_t
7848 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
7849 {
7850 /*
7851 * If we are evicting all the buffers for this device, which happens
7852 * at pool export time, schedule asynchronous task
7853 */
7854 if (all && zfs_l2arc_async_evict) {
7855 if ((taskq_dispatch(arc_flush_taskq, l2arc_evict_task,
7856 dev, TQ_NOSLEEP) == NULL)) {
7857 /*
7858 * Failed to dispatch asynchronous task
7859 * cleanup, evict synchronously
7860 */
7861 l2arc_evict_impl(dev, distance, all);
7862 } else {
7863 /*
7864 * Successful dispatch, vdev space updated
7865 */
7866 return (B_TRUE);
7867 }
7868 } else {
7869 /* Evict synchronously */
7870 l2arc_evict_impl(dev, distance, all);
7871 }
7872
7873 return (B_FALSE);
7874 }
7875
7876 /*
7877 * Find and write ARC buffers to the L2ARC device.
7878 *
7879 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
7880 * for reading until they have completed writing.
7881 * The headroom_boost is an in-out parameter used to maintain headroom boost
7882 * state between calls to this function.
7883 *
7884 * Returns the number of bytes actually written (which may be smaller than
7885 * the delta by which the device hand has changed due to alignment).
7886 */
7887 static uint64_t
7888 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
7889 l2ad_feed_t feed_type)
7890 {
7891 arc_buf_hdr_t *hdr, *hdr_prev, *head;
7892 /*
7893 * We must carefully track the space we deal with here:
7894 * - write_size: sum of the size of all buffers to be written
7895 * without compression or inter-buffer alignment applied.
7896 * This size is added to arcstat_l2_size, because subsequent
7897 * eviction of buffers decrements this kstat by only the
7898 * buffer's b_lsize (which doesn't take alignment into account).
7899 * - write_asize: sum of the size of all buffers to be written
7900 * with inter-buffer alignment applied.
7901 * This size is used to estimate the maximum number of bytes
7902 * we could take up on the device and is thus used to gauge how
7903 * close we are to hitting target_sz.
7904 */
7905 uint64_t write_asize, write_psize, write_lsize, headroom;
7906 boolean_t full;
7907 l2arc_write_callback_t *cb;
7908 zio_t *pio, *wzio;
7909 enum l2arc_priorities try;
7910 uint64_t guid = spa_load_guid(spa);
7911 boolean_t dev_hdr_update = B_FALSE;
7912
7913 ASSERT3P(dev->l2ad_vdev, !=, NULL);
7914
7915 pio = NULL;
7916 cb = NULL;
7917 write_lsize = write_asize = write_psize = 0;
7918 full = B_FALSE;
7919 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
7920 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
7921
7922 /*
7923 * Copy buffers for L2ARC writing.
7924 */
7925 for (try = PRIORITY_MFU_DDT; try < PRIORITY_NUMTYPES; try++) {
7926 multilist_sublist_t *mls = l2arc_sublist_lock(try);
7927 uint64_t passed_sz = 0;
7928
7929 /*
7930 * L2ARC fast warmup.
7931 *
7932 * Until the ARC is warm and starts to evict, read from the
7933 * head of the ARC lists rather than the tail.
7934 */
7935 if (arc_warm == B_FALSE)
7936 hdr = multilist_sublist_head(mls);
7937 else
7938 hdr = multilist_sublist_tail(mls);
7939
7940 headroom = target_sz * l2arc_headroom;
7941 if (zfs_compressed_arc_enabled)
7942 headroom = (headroom * l2arc_headroom_boost) / 100;
7943
7944 for (; hdr; hdr = hdr_prev) {
7945 kmutex_t *hash_lock;
7946
7947 if (arc_warm == B_FALSE)
7948 hdr_prev = multilist_sublist_next(mls, hdr);
7949 else
7950 hdr_prev = multilist_sublist_prev(mls, hdr);
7951
7952 hash_lock = HDR_LOCK(hdr);
7953 if (!mutex_tryenter(hash_lock)) {
7954 /*
7955 * Skip this buffer rather than waiting.
7956 */
7957 continue;
7958 }
7959
7960 passed_sz += HDR_GET_LSIZE(hdr);
7961 if (passed_sz > headroom) {
7962 /*
7963 * Searched too far.
7964 */
7965 mutex_exit(hash_lock);
7966 break;
7967 }
7968
7969 if (!l2arc_write_eligible(guid, hdr)) {
7970 mutex_exit(hash_lock);
7971 continue;
7972 }
7973
7974 /*
7975 * We rely on the L1 portion of the header below, so
7976 * it's invalid for this header to have been evicted out
7977 * of the ghost cache, prior to being written out. The
7978 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
7979 */
7980 ASSERT(HDR_HAS_L1HDR(hdr));
7981
7982 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
7983 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
7984 ASSERT3U(arc_hdr_size(hdr), >, 0);
7985 uint64_t psize = arc_hdr_size(hdr);
7986 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
7987 psize);
7988
7989 if ((write_asize + asize) > target_sz) {
7990 full = B_TRUE;
7991 mutex_exit(hash_lock);
7992 break;
7993 }
7994
7995 /* make sure buf we select corresponds to feed_type */
7996 if ((feed_type == L2ARC_FEED_DDT_DEV &&
7997 arc_buf_type(hdr) != ARC_BUFC_DDT) ||
7998 (feed_type == L2ARC_FEED_NON_DDT_DEV &&
7999 arc_buf_type(hdr) == ARC_BUFC_DDT)) {
8000 mutex_exit(hash_lock);
8001 continue;
8002 }
8003
8004 if (pio == NULL) {
8005 /*
8006 * Insert a dummy header on the buflist so
8007 * l2arc_write_done() can find where the
8008 * write buffers begin without searching.
8009 */
8010 mutex_enter(&dev->l2ad_mtx);
8011 list_insert_head(&dev->l2ad_buflist, head);
8012 mutex_exit(&dev->l2ad_mtx);
8013
8014 cb = kmem_zalloc(
8015 sizeof (l2arc_write_callback_t), KM_SLEEP);
8016 cb->l2wcb_dev = dev;
8017 cb->l2wcb_head = head;
8018 list_create(&cb->l2wcb_log_blk_buflist,
8019 sizeof (l2arc_log_blk_buf_t),
8020 offsetof(l2arc_log_blk_buf_t, lbb_node));
8021 pio = zio_root(spa, l2arc_write_done, cb,
8022 ZIO_FLAG_CANFAIL);
8023 }
8024
8025 hdr->b_l2hdr.b_dev = dev;
8026 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
8027 arc_hdr_set_flags(hdr,
8028 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);
8029
8030 mutex_enter(&dev->l2ad_mtx);
8031 list_insert_head(&dev->l2ad_buflist, hdr);
8032 mutex_exit(&dev->l2ad_mtx);
8033
8034 (void) refcount_add_many(&dev->l2ad_alloc, psize, hdr);
8035
8036 /*
8037 * Normally the L2ARC can use the hdr's data, but if
8038 * we're sharing data between the hdr and one of its
8039 * bufs, L2ARC needs its own copy of the data so that
8040 * the ZIO below can't race with the buf consumer.
8041 * Another case where we need to create a copy of the
8042 * data is when the buffer size is not device-aligned
8043 * and we need to pad the block to make it such.
8044 * That also keeps the clock hand suitably aligned.
8045 *
8046 * To ensure that the copy will be available for the
8047 * lifetime of the ZIO and be cleaned up afterwards, we
8048 * add it to the l2arc_free_on_write queue.
8049 */
8050 abd_t *to_write;
8051 if (!HDR_SHARED_DATA(hdr) && psize == asize) {
8052 to_write = hdr->b_l1hdr.b_pabd;
8053 } else {
8054 to_write = abd_alloc_for_io(asize,
8055 !HDR_ISTYPE_DATA(hdr));
8056 abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize);
8057 if (asize != psize) {
8058 abd_zero_off(to_write, psize,
8059 asize - psize);
8060 }
8061 l2arc_free_abd_on_write(to_write, asize,
8062 arc_buf_type(hdr));
8063 }
8064 wzio = zio_write_phys(pio, dev->l2ad_vdev,
8065 hdr->b_l2hdr.b_daddr, asize, to_write,
8066 ZIO_CHECKSUM_OFF, NULL, hdr,
8067 ZIO_PRIORITY_ASYNC_WRITE,
8068 ZIO_FLAG_CANFAIL, B_FALSE);
8069
8070 write_lsize += HDR_GET_LSIZE(hdr);
8071 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
8072 zio_t *, wzio);
8073
8074 write_psize += psize;
8075 write_asize += asize;
8076 dev->l2ad_hand += asize;
8077
8078 mutex_exit(hash_lock);
8079
8080 (void) zio_nowait(wzio);
8081
8082 /*
8083 * Append buf info to current log and commit if full.
8084 * arcstat_l2_{size,asize} kstats are updated internally.
8085 */
8086 if (l2arc_log_blk_insert(dev, hdr)) {
8087 l2arc_log_blk_commit(dev, pio, cb);
8088 dev_hdr_update = B_TRUE;
8089 }
8090 }
8091
8092 multilist_sublist_unlock(mls);
8093
8094 if (full == B_TRUE)
8095 break;
8096 }
8097
8098 /* No buffers selected for writing? */
8099 if (pio == NULL) {
8100 ASSERT0(write_lsize);
8101 ASSERT(!HDR_HAS_L1HDR(head));
8102 kmem_cache_free(hdr_l2only_cache, head);
8103 return (0);
8104 }
8105
8106 /*
8107 * If we wrote any logs as part of this write, update dev hdr
8108 * to point to it.
8109 */
8110 if (dev_hdr_update)
8111 l2arc_dev_hdr_update(dev, pio);
8112
8113 ASSERT3U(write_asize, <=, target_sz);
8114 ARCSTAT_BUMP(arcstat_l2_writes_sent);
8115 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize);
8116 if (feed_type == L2ARC_FEED_DDT_DEV)
8117 ARCSTAT_INCR(arcstat_l2_ddt_write_bytes, write_psize);
8118 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize);
8119 ARCSTAT_INCR(arcstat_l2_psize, write_psize);
8120 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
8121
8122 /*
8123 * Bump device hand to the device start if it is approaching the end.
8124 * l2arc_evict() will already have evicted ahead for this case.
8125 */
8126 if (dev->l2ad_hand + target_sz + l2arc_log_blk_overhead(target_sz) >=
8127 dev->l2ad_end) {
8128 dev->l2ad_hand = dev->l2ad_start;
8129 dev->l2ad_first = B_FALSE;
8130 }
8131
8132 dev->l2ad_writing = B_TRUE;
8133 (void) zio_wait(pio);
8134 dev->l2ad_writing = B_FALSE;
8135
8136 return (write_asize);
8137 }
8138
8139 static boolean_t
8140 l2arc_feed_dev(l2ad_feed_t feed_type, uint64_t *wrote)
8141 {
8142 spa_t *spa;
8143 l2arc_dev_t *dev;
8144 uint64_t size;
8145
8146 /*
8147 * This selects the next l2arc device to write to, and in
8148 * doing so the next spa to feed from: dev->l2ad_spa. This
8149 * will return NULL if there are now no l2arc devices or if
8150 * they are all faulted.
8151 *
8152 * If a device is returned, its spa's config lock is also
8153 * held to prevent device removal. l2arc_dev_get_next()
8154 * will grab and release l2arc_dev_mtx.
8155 */
8156 if ((dev = l2arc_dev_get_next(feed_type)) == NULL)
8157 return (B_FALSE);
8158
8159 spa = dev->l2ad_spa;
8160 ASSERT(spa != NULL);
8161
8162 /*
8163 * If the pool is read-only - skip it
8164 */
8165 if (!spa_writeable(spa)) {
8166 spa_config_exit(spa, SCL_L2ARC, dev);
8167 return (B_FALSE);
8168 }
8169
8170 ARCSTAT_BUMP(arcstat_l2_feeds);
8171 size = l2arc_write_size();
8172
8173 /*
8174 * Evict L2ARC buffers that will be overwritten.
8175 * B_FALSE guarantees synchronous eviction.
8176 */
8177 (void) l2arc_evict(dev, size, B_FALSE);
8178
8179 /*
8180 * Write ARC buffers.
8181 */
8182 *wrote = l2arc_write_buffers(spa, dev, size, feed_type);
8183
8184 spa_config_exit(spa, SCL_L2ARC, dev);
8185
8186 return (B_TRUE);
8187 }
8188
8189 /*
8190 * This thread feeds the L2ARC at regular intervals. This is the beating
8191 * heart of the L2ARC.
8192 */
8193 /* ARGSUSED */
8194 static void
8195 l2arc_feed_thread(void *unused)
8196 {
8197 callb_cpr_t cpr;
8198 uint64_t size, total_written = 0;
8199 clock_t begin, next = ddi_get_lbolt();
8200 l2ad_feed_t feed_type = L2ARC_FEED_ALL;
8201
8202 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
8203
8204 mutex_enter(&l2arc_feed_thr_lock);
8205
8206 while (l2arc_thread_exit == 0) {
8207 CALLB_CPR_SAFE_BEGIN(&cpr);
8208 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
8209 next);
8210 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
8211 next = ddi_get_lbolt() + hz;
8212
8213 /*
8214 * Quick check for L2ARC devices.
8215 */
8216 mutex_enter(&l2arc_dev_mtx);
8217 if (l2arc_ndev == 0) {
8218 mutex_exit(&l2arc_dev_mtx);
8219 continue;
8220 }
8221 mutex_exit(&l2arc_dev_mtx);
8222 begin = ddi_get_lbolt();
8223
8224 /*
8225 * Avoid contributing to memory pressure.
8226 */
8227 if (arc_reclaim_needed()) {
8228 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
8229 continue;
8230 }
8231
8232 /* try to write to DDT L2ARC device if any */
8233 if (l2arc_feed_dev(L2ARC_FEED_DDT_DEV, &size)) {
8234 total_written += size;
8235 feed_type = L2ARC_FEED_NON_DDT_DEV;
8236 }
8237
8238 /* try to write to the regular L2ARC device if any */
8239 if (l2arc_feed_dev(feed_type, &size)) {
8240 total_written += size;
8241 if (feed_type == L2ARC_FEED_NON_DDT_DEV)
8242 total_written /= 2; /* avg written per device */
8243 }
8244
8245 /*
8246 * Calculate interval between writes.
8247 */
8248 next = l2arc_write_interval(begin, l2arc_write_size(),
8249 total_written);
8250
8251 total_written = 0;
8252 }
8253
8254 l2arc_thread_exit = 0;
8255 cv_broadcast(&l2arc_feed_thr_cv);
8256 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
8257 thread_exit();
8258 }
8259
8260 boolean_t
8261 l2arc_vdev_present(vdev_t *vd)
8262 {
8263 return (l2arc_vdev_get(vd) != NULL);
8264 }
8265
8266 /*
8267 * Returns the l2arc_dev_t associated with a particular vdev_t or NULL if
8268 * the vdev_t isn't an L2ARC device.
8269 */
8270 static l2arc_dev_t *
8271 l2arc_vdev_get(vdev_t *vd)
8272 {
8273 l2arc_dev_t *dev;
8274 boolean_t held = MUTEX_HELD(&l2arc_dev_mtx);
8275
8276 if (!held)
8277 mutex_enter(&l2arc_dev_mtx);
8278 for (dev = list_head(l2arc_dev_list); dev != NULL;
8279 dev = list_next(l2arc_dev_list, dev)) {
8280 if (dev->l2ad_vdev == vd)
8281 break;
8282 }
8283 if (!held)
8284 mutex_exit(&l2arc_dev_mtx);
8285
8286 return (dev);
8287 }
8288
8289 /*
8290 * Add a vdev for use by the L2ARC. By this point the spa has already
8291 * validated the vdev and opened it. The `rebuild' flag indicates whether
8292 * we should attempt an L2ARC persistency rebuild.
8293 */
8294 void
8295 l2arc_add_vdev(spa_t *spa, vdev_t *vd, boolean_t rebuild)
8296 {
8297 l2arc_dev_t *adddev;
8298
8299 ASSERT(!l2arc_vdev_present(vd));
8300
8301 /*
8302 * Create a new l2arc device entry.
8303 */
8304 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
8305 adddev->l2ad_spa = spa;
8306 adddev->l2ad_vdev = vd;
8307 /* leave extra size for an l2arc device header */
8308 adddev->l2ad_dev_hdr_asize = MAX(sizeof (*adddev->l2ad_dev_hdr),
8309 1 << vd->vdev_ashift);
8310 adddev->l2ad_start = VDEV_LABEL_START_SIZE + adddev->l2ad_dev_hdr_asize;
8311 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
8312 ASSERT3U(adddev->l2ad_start, <, adddev->l2ad_end);
8313 adddev->l2ad_hand = adddev->l2ad_start;
8314 adddev->l2ad_first = B_TRUE;
8315 adddev->l2ad_writing = B_FALSE;
8316 adddev->l2ad_dev_hdr = kmem_zalloc(adddev->l2ad_dev_hdr_asize,
8317 KM_SLEEP);
8318
8319 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
8320 /*
8321 * This is a list of all ARC buffers that are still valid on the
8322 * device.
8323 */
8324 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
8325 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
8326
8327 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
8328 refcount_create(&adddev->l2ad_alloc);
8329
8330 /*
8331 * Add device to global list
8332 */
8333 mutex_enter(&l2arc_dev_mtx);
8334 list_insert_head(l2arc_dev_list, adddev);
8335 atomic_inc_64(&l2arc_ndev);
8336 if (rebuild && l2arc_rebuild_enabled &&
8337 adddev->l2ad_end - adddev->l2ad_start > L2ARC_PERSIST_MIN_SIZE) {
8338 /*
8339 * Just mark the device as pending for a rebuild. We won't
8340 * be starting a rebuild in line here as it would block pool
8341 * import. Instead spa_load_impl will hand that off to an
8342 * async task which will call l2arc_spa_rebuild_start.
8343 */
8344 adddev->l2ad_rebuild = B_TRUE;
8345 }
8346 mutex_exit(&l2arc_dev_mtx);
8347 }
8348
8349 /*
8350 * Remove a vdev from the L2ARC.
8351 */
8352 void
8353 l2arc_remove_vdev(vdev_t *vd)
8354 {
8355 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
8356
8357 /*
8358 * Find the device by vdev
8359 */
8360 mutex_enter(&l2arc_dev_mtx);
8361 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
8362 nextdev = list_next(l2arc_dev_list, dev);
8363 if (vd == dev->l2ad_vdev) {
8364 remdev = dev;
8365 break;
8366 }
8367 }
8368 ASSERT3P(remdev, !=, NULL);
8369
8370 /*
8371 * Cancel any ongoing or scheduled rebuild (race protection with
8372 * l2arc_spa_rebuild_start provided via l2arc_dev_mtx).
8373 */
8374 remdev->l2ad_rebuild_cancel = B_TRUE;
8375 if (remdev->l2ad_rebuild_did != 0) {
8376 /*
8377 * N.B. it should be safe to thread_join with the rebuild
8378 * thread while holding l2arc_dev_mtx because it is not
8379 * accessed from anywhere in the l2arc rebuild code below
8380 * (except for l2arc_spa_rebuild_start, which is ok).
8381 */
8382 thread_join(remdev->l2ad_rebuild_did);
8383 }
8384
8385 /*
8386 * Remove device from global list
8387 */
8388 list_remove(l2arc_dev_list, remdev);
8389 l2arc_dev_last = NULL; /* may have been invalidated */
8390 l2arc_ddt_dev_last = NULL; /* may have been invalidated */
8391 atomic_dec_64(&l2arc_ndev);
8392 mutex_exit(&l2arc_dev_mtx);
8393
8394 if (vdev_type_is_ddt(remdev->l2ad_vdev))
8395 atomic_add_64(&remdev->l2ad_spa->spa_l2arc_ddt_devs_size,
8396 -(vdev_get_min_asize(remdev->l2ad_vdev)));
8397
8398 /*
8399 * Clear all buflists and ARC references. L2ARC device flush.
8400 */
8401 if (l2arc_evict(remdev, 0, B_TRUE) == B_FALSE) {
8402 /*
8403 * The eviction was done synchronously, cleanup here
8404 * Otherwise, the asynchronous task will cleanup
8405 */
8406 list_destroy(&remdev->l2ad_buflist);
8407 mutex_destroy(&remdev->l2ad_mtx);
8408 kmem_free(remdev->l2ad_dev_hdr, remdev->l2ad_dev_hdr_asize);
8409 kmem_free(remdev, sizeof (l2arc_dev_t));
8410 }
8411 }
8412
8413 void
8414 l2arc_init(void)
8415 {
8416 l2arc_thread_exit = 0;
8417 l2arc_ndev = 0;
8418 l2arc_writes_sent = 0;
8419 l2arc_writes_done = 0;
8420
8421 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
8422 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
8423 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
8424 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
8425
8426 l2arc_dev_list = &L2ARC_dev_list;
8427 l2arc_free_on_write = &L2ARC_free_on_write;
8428 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
8429 offsetof(l2arc_dev_t, l2ad_node));
8430 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
8431 offsetof(l2arc_data_free_t, l2df_list_node));
8432 }
8433
8434 void
8435 l2arc_fini(void)
8436 {
8437 /*
8438 * This is called from dmu_fini(), which is called from spa_fini();
8439 * Because of this, we can assume that all l2arc devices have
8440 * already been removed when the pools themselves were removed.
8441 */
8442
8443 l2arc_do_free_on_write();
8444
8445 mutex_destroy(&l2arc_feed_thr_lock);
8446 cv_destroy(&l2arc_feed_thr_cv);
8447 mutex_destroy(&l2arc_dev_mtx);
8448 mutex_destroy(&l2arc_free_on_write_mtx);
8449
8450 list_destroy(l2arc_dev_list);
8451 list_destroy(l2arc_free_on_write);
8452 }
8453
8454 void
8455 l2arc_start(void)
8456 {
8457 if (!(spa_mode_global & FWRITE))
8458 return;
8459
8460 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
8461 TS_RUN, minclsyspri);
8462 }
8463
8464 void
8465 l2arc_stop(void)
8466 {
8467 if (!(spa_mode_global & FWRITE))
8468 return;
8469
8470 mutex_enter(&l2arc_feed_thr_lock);
8471 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
8472 l2arc_thread_exit = 1;
8473 while (l2arc_thread_exit != 0)
8474 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
8475 mutex_exit(&l2arc_feed_thr_lock);
8476 }
8477
8478 /*
8479 * Punches out rebuild threads for the L2ARC devices in a spa. This should
8480 * be called after pool import from the spa async thread, since starting
8481 * these threads directly from spa_import() will make them part of the
8482 * "zpool import" context and delay process exit (and thus pool import).
8483 */
8484 void
8485 l2arc_spa_rebuild_start(spa_t *spa)
8486 {
8487 /*
8488 * Locate the spa's l2arc devices and kick off rebuild threads.
8489 */
8490 mutex_enter(&l2arc_dev_mtx);
8491 for (int i = 0; i < spa->spa_l2cache.sav_count; i++) {
8492 l2arc_dev_t *dev =
8493 l2arc_vdev_get(spa->spa_l2cache.sav_vdevs[i]);
8494 if (dev == NULL) {
8495 /* Don't attempt a rebuild if the vdev is UNAVAIL */
8496 continue;
8497 }
8498 if (dev->l2ad_rebuild && !dev->l2ad_rebuild_cancel) {
8499 VERIFY3U(dev->l2ad_rebuild_did, ==, 0);
8500 #ifdef _KERNEL
8501 dev->l2ad_rebuild_did = thread_create(NULL, 0,
8502 l2arc_dev_rebuild_start, dev, 0, &p0, TS_RUN,
8503 minclsyspri)->t_did;
8504 #endif
8505 }
8506 }
8507 mutex_exit(&l2arc_dev_mtx);
8508 }
8509
8510 /*
8511 * Main entry point for L2ARC rebuilding.
8512 */
8513 static void
8514 l2arc_dev_rebuild_start(l2arc_dev_t *dev)
8515 {
8516 if (!dev->l2ad_rebuild_cancel) {
8517 VERIFY(dev->l2ad_rebuild);
8518 (void) l2arc_rebuild(dev);
8519 dev->l2ad_rebuild = B_FALSE;
8520 }
8521 }
8522
8523 /*
8524 * This function implements the actual L2ARC metadata rebuild. It:
8525 *
8526 * 1) reads the device's header
8527 * 2) if a good device header is found, starts reading the log block chain
8528 * 3) restores each block's contents to memory (reconstructing arc_buf_hdr_t's)
8529 *
8530 * Operation stops under any of the following conditions:
8531 *
8532 * 1) We reach the end of the log blk chain (the back-reference in the blk is
8533 * invalid or loops over our starting point).
8534 * 2) We encounter *any* error condition (cksum errors, io errors, looped
8535 * blocks, etc.).
8536 */
8537 static int
8538 l2arc_rebuild(l2arc_dev_t *dev)
8539 {
8540 vdev_t *vd = dev->l2ad_vdev;
8541 spa_t *spa = vd->vdev_spa;
8542 int err;
8543 l2arc_log_blk_phys_t *this_lb, *next_lb;
8544 uint8_t *this_lb_buf, *next_lb_buf;
8545 zio_t *this_io = NULL, *next_io = NULL;
8546 l2arc_log_blkptr_t lb_ptrs[2];
8547 boolean_t first_pass, lock_held;
8548 uint64_t load_guid;
8549
8550 this_lb = kmem_zalloc(sizeof (*this_lb), KM_SLEEP);
8551 next_lb = kmem_zalloc(sizeof (*next_lb), KM_SLEEP);
8552 this_lb_buf = kmem_zalloc(sizeof (l2arc_log_blk_phys_t), KM_SLEEP);
8553 next_lb_buf = kmem_zalloc(sizeof (l2arc_log_blk_phys_t), KM_SLEEP);
8554
8555 /*
8556 * We prevent device removal while issuing reads to the device,
8557 * then during the rebuilding phases we drop this lock again so
8558 * that a spa_unload or device remove can be initiated - this is
8559 * safe, because the spa will signal us to stop before removing
8560 * our device and wait for us to stop.
8561 */
8562 spa_config_enter(spa, SCL_L2ARC, vd, RW_READER);
8563 lock_held = B_TRUE;
8564
8565 load_guid = spa_load_guid(dev->l2ad_vdev->vdev_spa);
8566 /*
8567 * Device header processing phase.
8568 */
8569 if ((err = l2arc_dev_hdr_read(dev)) != 0) {
8570 /* device header corrupted, start a new one */
8571 bzero(dev->l2ad_dev_hdr, dev->l2ad_dev_hdr_asize);
8572 goto out;
8573 }
8574
8575 /* Retrieve the persistent L2ARC device state */
8576 dev->l2ad_hand = vdev_psize_to_asize(dev->l2ad_vdev,
8577 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr +
8578 LBP_GET_PSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0]));
8579 dev->l2ad_first = !!(dev->l2ad_dev_hdr->dh_flags &
8580 L2ARC_DEV_HDR_EVICT_FIRST);
8581
8582 /* Prepare the rebuild processing state */
8583 bcopy(dev->l2ad_dev_hdr->dh_start_lbps, lb_ptrs, sizeof (lb_ptrs));
8584 first_pass = B_TRUE;
8585
8586 /* Start the rebuild process */
8587 for (;;) {
8588 if (!l2arc_log_blkptr_valid(dev, &lb_ptrs[0]))
8589 /* We hit an invalid block address, end the rebuild. */
8590 break;
8591
8592 if ((err = l2arc_log_blk_read(dev, &lb_ptrs[0], &lb_ptrs[1],
8593 this_lb, next_lb, this_lb_buf, next_lb_buf,
8594 this_io, &next_io)) != 0)
8595 break;
8596
8597 spa_config_exit(spa, SCL_L2ARC, vd);
8598 lock_held = B_FALSE;
8599
8600 /* Protection against infinite loops of log blocks. */
8601 if (l2arc_range_check_overlap(lb_ptrs[1].lbp_daddr,
8602 lb_ptrs[0].lbp_daddr,
8603 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr) &&
8604 !first_pass) {
8605 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_loop_errors);
8606 err = SET_ERROR(ELOOP);
8607 break;
8608 }
8609
8610 /*
8611 * Our memory pressure valve. If the system is running low
8612 * on memory, rather than swamping memory with new ARC buf
8613 * hdrs, we opt not to rebuild the L2ARC. At this point,
8614 * however, we have already set up our L2ARC dev to chain in
8615 * new metadata log blk, so the user may choose to re-add the
8616 * L2ARC dev at a later time to reconstruct it (when there's
8617 * less memory pressure).
8618 */
8619 if (arc_reclaim_needed()) {
8620 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_lowmem);
8621 cmn_err(CE_NOTE, "System running low on memory, "
8622 "aborting L2ARC rebuild.");
8623 err = SET_ERROR(ENOMEM);
8624 break;
8625 }
8626
8627 /*
8628 * Now that we know that the next_lb checks out alright, we
8629 * can start reconstruction from this lb - we can be sure
8630 * that the L2ARC write hand has not yet reached any of our
8631 * buffers.
8632 */
8633 l2arc_log_blk_restore(dev, load_guid, this_lb,
8634 LBP_GET_PSIZE(&lb_ptrs[0]));
8635
8636 /*
8637 * End of list detection. We can look ahead two steps in the
8638 * blk chain and if the 2nd blk from this_lb dips below the
8639 * initial chain starting point, then we know two things:
8640 * 1) it can't be valid, and
8641 * 2) the next_lb's ARC entries might have already been
8642 * partially overwritten and so we should stop before
8643 * we restore it
8644 */
8645 if (l2arc_range_check_overlap(
8646 this_lb->lb_back2_lbp.lbp_daddr, lb_ptrs[0].lbp_daddr,
8647 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr) &&
8648 !first_pass)
8649 break;
8650
8651 /* log blk restored, continue with next one in the list */
8652 lb_ptrs[0] = lb_ptrs[1];
8653 lb_ptrs[1] = this_lb->lb_back2_lbp;
8654 PTR_SWAP(this_lb, next_lb);
8655 PTR_SWAP(this_lb_buf, next_lb_buf);
8656 this_io = next_io;
8657 next_io = NULL;
8658 first_pass = B_FALSE;
8659
8660 for (;;) {
8661 if (dev->l2ad_rebuild_cancel) {
8662 err = SET_ERROR(ECANCELED);
8663 goto out;
8664 }
8665 if (spa_config_tryenter(spa, SCL_L2ARC, vd,
8666 RW_READER)) {
8667 lock_held = B_TRUE;
8668 break;
8669 }
8670 /*
8671 * L2ARC config lock held by somebody in writer,
8672 * possibly due to them trying to remove us. They'll
8673 * likely to want us to shut down, so after a little
8674 * delay, we check l2ad_rebuild_cancel and retry
8675 * the lock again.
8676 */
8677 delay(1);
8678 }
8679 }
8680 out:
8681 if (next_io != NULL)
8682 l2arc_log_blk_prefetch_abort(next_io);
8683 kmem_free(this_lb, sizeof (*this_lb));
8684 kmem_free(next_lb, sizeof (*next_lb));
8685 kmem_free(this_lb_buf, sizeof (l2arc_log_blk_phys_t));
8686 kmem_free(next_lb_buf, sizeof (l2arc_log_blk_phys_t));
8687 if (err == 0)
8688 ARCSTAT_BUMP(arcstat_l2_rebuild_successes);
8689
8690 if (lock_held)
8691 spa_config_exit(spa, SCL_L2ARC, vd);
8692
8693 return (err);
8694 }
8695
8696 /*
8697 * Attempts to read the device header on the provided L2ARC device and writes
8698 * it to `hdr'. On success, this function returns 0, otherwise the appropriate
8699 * error code is returned.
8700 */
8701 static int
8702 l2arc_dev_hdr_read(l2arc_dev_t *dev)
8703 {
8704 int err;
8705 uint64_t guid;
8706 zio_cksum_t cksum;
8707 l2arc_dev_hdr_phys_t *hdr = dev->l2ad_dev_hdr;
8708 const uint64_t hdr_asize = dev->l2ad_dev_hdr_asize;
8709 abd_t *abd;
8710
8711 guid = spa_guid(dev->l2ad_vdev->vdev_spa);
8712
8713 abd = abd_get_from_buf(hdr, hdr_asize);
8714 err = zio_wait(zio_read_phys(NULL, dev->l2ad_vdev,
8715 VDEV_LABEL_START_SIZE, hdr_asize, abd,
8716 ZIO_CHECKSUM_OFF, NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
8717 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
8718 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE));
8719 abd_put(abd);
8720 if (err != 0) {
8721 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors);
8722 return (err);
8723 }
8724
8725 if (hdr->dh_magic == BSWAP_64(L2ARC_DEV_HDR_MAGIC_V1))
8726 byteswap_uint64_array(hdr, sizeof (*hdr));
8727
8728 if (hdr->dh_magic != L2ARC_DEV_HDR_MAGIC_V1 ||
8729 hdr->dh_spa_guid != guid) {
8730 /*
8731 * Attempt to rebuild a device containing no actual dev hdr
8732 * or containing a header from some other pool.
8733 */
8734 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_unsupported);
8735 return (SET_ERROR(ENOTSUP));
8736 }
8737
8738 l2arc_dev_hdr_checksum(hdr, &cksum);
8739 if (!ZIO_CHECKSUM_EQUAL(hdr->dh_self_cksum, cksum)) {
8740 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_errors);
8741 return (SET_ERROR(EINVAL));
8742 }
8743
8744 return (0);
8745 }
8746
8747 /*
8748 * Reads L2ARC log blocks from storage and validates their contents.
8749 *
8750 * This function implements a simple prefetcher to make sure that while
8751 * we're processing one buffer the L2ARC is already prefetching the next
8752 * one in the chain.
8753 *
8754 * The arguments this_lp and next_lp point to the current and next log blk
8755 * address in the block chain. Similarly, this_lb and next_lb hold the
8756 * l2arc_log_blk_phys_t's of the current and next L2ARC blk. The this_lb_buf
8757 * and next_lb_buf must be buffers of appropriate to hold a raw
8758 * l2arc_log_blk_phys_t (they are used as catch buffers for read ops prior
8759 * to buffer decompression).
8760 *
8761 * The `this_io' and `next_io' arguments are used for block prefetching.
8762 * When issuing the first blk IO during rebuild, you should pass NULL for
8763 * `this_io'. This function will then issue a sync IO to read the block and
8764 * also issue an async IO to fetch the next block in the block chain. The
8765 * prefetch IO is returned in `next_io'. On subsequent calls to this
8766 * function, pass the value returned in `next_io' from the previous call
8767 * as `this_io' and a fresh `next_io' pointer to hold the next prefetch IO.
8768 * Prior to the call, you should initialize your `next_io' pointer to be
8769 * NULL. If no prefetch IO was issued, the pointer is left set at NULL.
8770 *
8771 * On success, this function returns 0, otherwise it returns an appropriate
8772 * error code. On error the prefetching IO is aborted and cleared before
8773 * returning from this function. Therefore, if we return `success', the
8774 * caller can assume that we have taken care of cleanup of prefetch IOs.
8775 */
8776 static int
8777 l2arc_log_blk_read(l2arc_dev_t *dev,
8778 const l2arc_log_blkptr_t *this_lbp, const l2arc_log_blkptr_t *next_lbp,
8779 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb,
8780 uint8_t *this_lb_buf, uint8_t *next_lb_buf,
8781 zio_t *this_io, zio_t **next_io)
8782 {
8783 int err = 0;
8784 zio_cksum_t cksum;
8785
8786 ASSERT(this_lbp != NULL && next_lbp != NULL);
8787 ASSERT(this_lb != NULL && next_lb != NULL);
8788 ASSERT(this_lb_buf != NULL && next_lb_buf != NULL);
8789 ASSERT(next_io != NULL && *next_io == NULL);
8790 ASSERT(l2arc_log_blkptr_valid(dev, this_lbp));
8791
8792 /*
8793 * Check to see if we have issued the IO for this log blk in a
8794 * previous run. If not, this is the first call, so issue it now.
8795 */
8796 if (this_io == NULL) {
8797 this_io = l2arc_log_blk_prefetch(dev->l2ad_vdev, this_lbp,
8798 this_lb_buf);
8799 }
8800
8801 /*
8802 * Peek to see if we can start issuing the next IO immediately.
8803 */
8804 if (l2arc_log_blkptr_valid(dev, next_lbp)) {
8805 /*
8806 * Start issuing IO for the next log blk early - this
8807 * should help keep the L2ARC device busy while we
8808 * decompress and restore this log blk.
8809 */
8810 *next_io = l2arc_log_blk_prefetch(dev->l2ad_vdev, next_lbp,
8811 next_lb_buf);
8812 }
8813
8814 /* Wait for the IO to read this log block to complete */
8815 if ((err = zio_wait(this_io)) != 0) {
8816 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors);
8817 goto cleanup;
8818 }
8819
8820 /* Make sure the buffer checks out */
8821 fletcher_4_native(this_lb_buf, LBP_GET_PSIZE(this_lbp), NULL, &cksum);
8822 if (!ZIO_CHECKSUM_EQUAL(cksum, this_lbp->lbp_cksum)) {
8823 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_errors);
8824 err = SET_ERROR(EINVAL);
8825 goto cleanup;
8826 }
8827
8828 /* Now we can take our time decoding this buffer */
8829 switch (LBP_GET_COMPRESS(this_lbp)) {
8830 case ZIO_COMPRESS_OFF:
8831 bcopy(this_lb_buf, this_lb, sizeof (*this_lb));
8832 break;
8833 case ZIO_COMPRESS_LZ4:
8834 err = zio_decompress_data_buf(LBP_GET_COMPRESS(this_lbp),
8835 this_lb_buf, this_lb, LBP_GET_PSIZE(this_lbp),
8836 sizeof (*this_lb));
8837 if (err != 0) {
8838 err = SET_ERROR(EINVAL);
8839 goto cleanup;
8840 }
8841
8842 break;
8843 default:
8844 err = SET_ERROR(EINVAL);
8845 break;
8846 }
8847
8848 if (this_lb->lb_magic == BSWAP_64(L2ARC_LOG_BLK_MAGIC))
8849 byteswap_uint64_array(this_lb, sizeof (*this_lb));
8850
8851 if (this_lb->lb_magic != L2ARC_LOG_BLK_MAGIC) {
8852 err = SET_ERROR(EINVAL);
8853 goto cleanup;
8854 }
8855
8856 cleanup:
8857 /* Abort an in-flight prefetch I/O in case of error */
8858 if (err != 0 && *next_io != NULL) {
8859 l2arc_log_blk_prefetch_abort(*next_io);
8860 *next_io = NULL;
8861 }
8862 return (err);
8863 }
8864
8865 /*
8866 * Restores the payload of a log blk to ARC. This creates empty ARC hdr
8867 * entries which only contain an l2arc hdr, essentially restoring the
8868 * buffers to their L2ARC evicted state. This function also updates space
8869 * usage on the L2ARC vdev to make sure it tracks restored buffers.
8870 */
8871 static void
8872 l2arc_log_blk_restore(l2arc_dev_t *dev, uint64_t load_guid,
8873 const l2arc_log_blk_phys_t *lb, uint64_t lb_psize)
8874 {
8875 uint64_t size = 0, psize = 0;
8876
8877 for (int i = L2ARC_LOG_BLK_ENTRIES - 1; i >= 0; i--) {
8878 /*
8879 * Restore goes in the reverse temporal direction to preserve
8880 * correct temporal ordering of buffers in the l2ad_buflist.
8881 * l2arc_hdr_restore also does a list_insert_tail instead of
8882 * list_insert_head on the l2ad_buflist:
8883 *
8884 * LIST l2ad_buflist LIST
8885 * HEAD <------ (time) ------ TAIL
8886 * direction +-----+-----+-----+-----+-----+ direction
8887 * of l2arc <== | buf | buf | buf | buf | buf | ===> of rebuild
8888 * fill +-----+-----+-----+-----+-----+
8889 * ^ ^
8890 * | |
8891 * | |
8892 * l2arc_fill_thread l2arc_rebuild
8893 * places new bufs here restores bufs here
8894 *
8895 * This also works when the restored bufs get evicted at any
8896 * point during the rebuild.
8897 */
8898 l2arc_hdr_restore(&lb->lb_entries[i], dev, load_guid);
8899 size += LE_GET_LSIZE(&lb->lb_entries[i]);
8900 psize += LE_GET_PSIZE(&lb->lb_entries[i]);
8901 }
8902
8903 /*
8904 * Record rebuild stats:
8905 * size In-memory size of restored buffer data in ARC
8906 * psize Physical size of restored buffers in the L2ARC
8907 * bufs # of ARC buffer headers restored
8908 * log_blks # of L2ARC log entries processed during restore
8909 */
8910 ARCSTAT_INCR(arcstat_l2_rebuild_size, size);
8911 ARCSTAT_INCR(arcstat_l2_rebuild_psize, psize);
8912 ARCSTAT_INCR(arcstat_l2_rebuild_bufs, L2ARC_LOG_BLK_ENTRIES);
8913 ARCSTAT_BUMP(arcstat_l2_rebuild_log_blks);
8914 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_size, lb_psize);
8915 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, psize / lb_psize);
8916 vdev_space_update(dev->l2ad_vdev, psize, 0, 0);
8917 }
8918
8919 /*
8920 * Restores a single ARC buf hdr from a log block. The ARC buffer is put
8921 * into a state indicating that it has been evicted to L2ARC.
8922 */
8923 static void
8924 l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, l2arc_dev_t *dev,
8925 uint64_t load_guid)
8926 {
8927 arc_buf_hdr_t *hdr, *exists;
8928 kmutex_t *hash_lock;
8929 arc_buf_contents_t type = LE_GET_TYPE(le);
8930
8931 /*
8932 * Do all the allocation before grabbing any locks, this lets us
8933 * sleep if memory is full and we don't have to deal with failed
8934 * allocations.
8935 */
8936 hdr = arc_buf_alloc_l2only(load_guid, type, dev, le->le_dva,
8937 le->le_daddr, LE_GET_LSIZE(le), LE_GET_PSIZE(le),
8938 le->le_birth, le->le_freeze_cksum, LE_GET_CHECKSUM(le),
8939 LE_GET_COMPRESS(le), LE_GET_ARC_COMPRESS(le));
8940
8941 ARCSTAT_INCR(arcstat_l2_lsize, HDR_GET_LSIZE(hdr));
8942 ARCSTAT_INCR(arcstat_l2_psize, arc_hdr_size(hdr));
8943
8944 mutex_enter(&dev->l2ad_mtx);
8945 /*
8946 * We connect the l2hdr to the hdr only after the hdr is in the hash
8947 * table, otherwise the rest of the arc hdr manipulation machinery
8948 * might get confused.
8949 */
8950 list_insert_tail(&dev->l2ad_buflist, hdr);
8951 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
8952 mutex_exit(&dev->l2ad_mtx);
8953
8954 exists = buf_hash_insert(hdr, &hash_lock);
8955 if (exists) {
8956 /* Buffer was already cached, no need to restore it. */
8957 arc_hdr_destroy(hdr);
8958 mutex_exit(hash_lock);
8959 ARCSTAT_BUMP(arcstat_l2_rebuild_bufs_precached);
8960 return;
8961 }
8962
8963 mutex_exit(hash_lock);
8964 }
8965
8966 /*
8967 * Used by PL2ARC related functions that do
8968 * async read/write
8969 */
8970 static void
8971 pl2arc_io_done(zio_t *zio)
8972 {
8973 abd_put(zio->io_private);
8974 zio->io_private = NULL;
8975 }
8976
8977 /*
8978 * Starts an asynchronous read IO to read a log block. This is used in log
8979 * block reconstruction to start reading the next block before we are done
8980 * decoding and reconstructing the current block, to keep the l2arc device
8981 * nice and hot with read IO to process.
8982 * The returned zio will contain a newly allocated memory buffers for the IO
8983 * data which should then be freed by the caller once the zio is no longer
8984 * needed (i.e. due to it having completed). If you wish to abort this
8985 * zio, you should do so using l2arc_log_blk_prefetch_abort, which takes
8986 * care of disposing of the allocated buffers correctly.
8987 */
8988 static zio_t *
8989 l2arc_log_blk_prefetch(vdev_t *vd, const l2arc_log_blkptr_t *lbp,
8990 uint8_t *lb_buf)
8991 {
8992 uint32_t psize;
8993 zio_t *pio;
8994 abd_t *abd;
8995
8996 psize = LBP_GET_PSIZE(lbp);
8997 ASSERT(psize <= sizeof (l2arc_log_blk_phys_t));
8998 pio = zio_root(vd->vdev_spa, NULL, NULL, ZIO_FLAG_DONT_CACHE |
8999 ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE |
9000 ZIO_FLAG_DONT_RETRY);
9001 abd = abd_get_from_buf(lb_buf, psize);
9002 (void) zio_nowait(zio_read_phys(pio, vd, lbp->lbp_daddr, psize,
9003 abd, ZIO_CHECKSUM_OFF, pl2arc_io_done, abd,
9004 ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
9005 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE));
9006
9007 return (pio);
9008 }
9009
9010 /*
9011 * Aborts a zio returned from l2arc_log_blk_prefetch and frees the data
9012 * buffers allocated for it.
9013 */
9014 static void
9015 l2arc_log_blk_prefetch_abort(zio_t *zio)
9016 {
9017 (void) zio_wait(zio);
9018 }
9019
9020 /*
9021 * Creates a zio to update the device header on an l2arc device. The zio is
9022 * initiated as a child of `pio'.
9023 */
9024 static void
9025 l2arc_dev_hdr_update(l2arc_dev_t *dev, zio_t *pio)
9026 {
9027 zio_t *wzio;
9028 abd_t *abd;
9029 l2arc_dev_hdr_phys_t *hdr = dev->l2ad_dev_hdr;
9030 const uint64_t hdr_asize = dev->l2ad_dev_hdr_asize;
9031
9032 hdr->dh_magic = L2ARC_DEV_HDR_MAGIC_V1;
9033 hdr->dh_spa_guid = spa_guid(dev->l2ad_vdev->vdev_spa);
9034 hdr->dh_alloc_space = refcount_count(&dev->l2ad_alloc);
9035 hdr->dh_flags = 0;
9036 if (dev->l2ad_first)
9037 hdr->dh_flags |= L2ARC_DEV_HDR_EVICT_FIRST;
9038
9039 /* checksum operation goes last */
9040 l2arc_dev_hdr_checksum(hdr, &hdr->dh_self_cksum);
9041
9042 abd = abd_get_from_buf(hdr, hdr_asize);
9043 wzio = zio_write_phys(pio, dev->l2ad_vdev, VDEV_LABEL_START_SIZE,
9044 hdr_asize, abd, ZIO_CHECKSUM_OFF, pl2arc_io_done, abd,
9045 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE);
9046 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio);
9047 (void) zio_nowait(wzio);
9048 }
9049
9050 /*
9051 * Commits a log block to the L2ARC device. This routine is invoked from
9052 * l2arc_write_buffers when the log block fills up.
9053 * This function allocates some memory to temporarily hold the serialized
9054 * buffer to be written. This is then released in l2arc_write_done.
9055 */
9056 static void
9057 l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio,
9058 l2arc_write_callback_t *cb)
9059 {
9060 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
9061 uint64_t psize, asize;
9062 l2arc_log_blk_buf_t *lb_buf;
9063 abd_t *abd;
9064 zio_t *wzio;
9065
9066 VERIFY(dev->l2ad_log_ent_idx == L2ARC_LOG_BLK_ENTRIES);
9067
9068 /* link the buffer into the block chain */
9069 lb->lb_back2_lbp = dev->l2ad_dev_hdr->dh_start_lbps[1];
9070 lb->lb_magic = L2ARC_LOG_BLK_MAGIC;
9071
9072 /* try to compress the buffer */
9073 lb_buf = kmem_zalloc(sizeof (*lb_buf), KM_SLEEP);
9074 list_insert_tail(&cb->l2wcb_log_blk_buflist, lb_buf);
9075 abd = abd_get_from_buf(lb, sizeof (*lb));
9076 psize = zio_compress_data(ZIO_COMPRESS_LZ4, abd, lb_buf->lbb_log_blk,
9077 sizeof (*lb));
9078 abd_put(abd);
9079 /* a log block is never entirely zero */
9080 ASSERT(psize != 0);
9081 asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
9082 ASSERT(asize <= sizeof (lb_buf->lbb_log_blk));
9083
9084 /*
9085 * Update the start log blk pointer in the device header to point
9086 * to the log block we're about to write.
9087 */
9088 dev->l2ad_dev_hdr->dh_start_lbps[1] =
9089 dev->l2ad_dev_hdr->dh_start_lbps[0];
9090 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr = dev->l2ad_hand;
9091 _NOTE(CONSTCOND)
9092 LBP_SET_LSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0], sizeof (*lb));
9093 LBP_SET_PSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0], asize);
9094 LBP_SET_CHECKSUM(&dev->l2ad_dev_hdr->dh_start_lbps[0],
9095 ZIO_CHECKSUM_FLETCHER_4);
9096 LBP_SET_TYPE(&dev->l2ad_dev_hdr->dh_start_lbps[0], 0);
9097
9098 if (asize < sizeof (*lb)) {
9099 /* compression succeeded */
9100 bzero(lb_buf->lbb_log_blk + psize, asize - psize);
9101 LBP_SET_COMPRESS(&dev->l2ad_dev_hdr->dh_start_lbps[0],
9102 ZIO_COMPRESS_LZ4);
9103 } else {
9104 /* compression failed */
9105 bcopy(lb, lb_buf->lbb_log_blk, sizeof (*lb));
9106 LBP_SET_COMPRESS(&dev->l2ad_dev_hdr->dh_start_lbps[0],
9107 ZIO_COMPRESS_OFF);
9108 }
9109
9110 /* checksum what we're about to write */
9111 fletcher_4_native(lb_buf->lbb_log_blk, asize,
9112 NULL, &dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_cksum);
9113
9114 /* perform the write itself */
9115 CTASSERT(L2ARC_LOG_BLK_SIZE >= SPA_MINBLOCKSIZE &&
9116 L2ARC_LOG_BLK_SIZE <= SPA_MAXBLOCKSIZE);
9117 abd = abd_get_from_buf(lb_buf->lbb_log_blk, asize);
9118 wzio = zio_write_phys(pio, dev->l2ad_vdev, dev->l2ad_hand,
9119 asize, abd, ZIO_CHECKSUM_OFF, pl2arc_io_done, abd,
9120 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE);
9121 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio);
9122 (void) zio_nowait(wzio);
9123
9124 dev->l2ad_hand += asize;
9125 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
9126
9127 /* bump the kstats */
9128 ARCSTAT_INCR(arcstat_l2_write_bytes, asize);
9129 ARCSTAT_BUMP(arcstat_l2_log_blk_writes);
9130 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_size, asize);
9131 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio,
9132 dev->l2ad_log_blk_payload_asize / asize);
9133
9134 /* start a new log block */
9135 dev->l2ad_log_ent_idx = 0;
9136 dev->l2ad_log_blk_payload_asize = 0;
9137 }
9138
9139 /*
9140 * Validates an L2ARC log blk address to make sure that it can be read
9141 * from the provided L2ARC device. Returns B_TRUE if the address is
9142 * within the device's bounds, or B_FALSE if not.
9143 */
9144 static boolean_t
9145 l2arc_log_blkptr_valid(l2arc_dev_t *dev, const l2arc_log_blkptr_t *lbp)
9146 {
9147 uint64_t psize = LBP_GET_PSIZE(lbp);
9148 uint64_t end = lbp->lbp_daddr + psize;
9149
9150 /*
9151 * A log block is valid if all of the following conditions are true:
9152 * - it fits entirely between l2ad_start and l2ad_end
9153 * - it has a valid size
9154 */
9155 return (lbp->lbp_daddr >= dev->l2ad_start && end <= dev->l2ad_end &&
9156 psize > 0 && psize <= sizeof (l2arc_log_blk_phys_t));
9157 }
9158
9159 /*
9160 * Computes the checksum of `hdr' and stores it in `cksum'.
9161 */
9162 static void
9163 l2arc_dev_hdr_checksum(const l2arc_dev_hdr_phys_t *hdr, zio_cksum_t *cksum)
9164 {
9165 fletcher_4_native((uint8_t *)hdr +
9166 offsetof(l2arc_dev_hdr_phys_t, dh_spa_guid),
9167 sizeof (*hdr) - offsetof(l2arc_dev_hdr_phys_t, dh_spa_guid),
9168 NULL, cksum);
9169 }
9170
9171 /*
9172 * Inserts ARC buffer `ab' into the current L2ARC log blk on the device.
9173 * The buffer being inserted must be present in L2ARC.
9174 * Returns B_TRUE if the L2ARC log blk is full and needs to be committed
9175 * to L2ARC, or B_FALSE if it still has room for more ARC buffers.
9176 */
9177 static boolean_t
9178 l2arc_log_blk_insert(l2arc_dev_t *dev, const arc_buf_hdr_t *ab)
9179 {
9180 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
9181 l2arc_log_ent_phys_t *le;
9182 int index = dev->l2ad_log_ent_idx++;
9183
9184 ASSERT(index < L2ARC_LOG_BLK_ENTRIES);
9185
9186 le = &lb->lb_entries[index];
9187 bzero(le, sizeof (*le));
9188 le->le_dva = ab->b_dva;
9189 le->le_birth = ab->b_birth;
9190 le->le_daddr = ab->b_l2hdr.b_daddr;
9191 LE_SET_LSIZE(le, HDR_GET_LSIZE(ab));
9192 LE_SET_PSIZE(le, HDR_GET_PSIZE(ab));
9193
9194 if ((ab->b_flags & ARC_FLAG_COMPRESSED_ARC) != 0) {
9195 LE_SET_ARC_COMPRESS(le, 1);
9196 LE_SET_COMPRESS(le, HDR_GET_COMPRESS(ab));
9197 } else {
9198 ASSERT3U(HDR_GET_COMPRESS(ab), ==, ZIO_COMPRESS_OFF);
9199 LE_SET_ARC_COMPRESS(le, 0);
9200 LE_SET_COMPRESS(le, ZIO_COMPRESS_OFF);
9201 }
9202
9203 if (ab->b_freeze_cksum != NULL) {
9204 le->le_freeze_cksum = *ab->b_freeze_cksum;
9205 LE_SET_CHECKSUM(le, ZIO_CHECKSUM_FLETCHER_2);
9206 } else {
9207 LE_SET_CHECKSUM(le, ZIO_CHECKSUM_OFF);
9208 }
9209
9210 LE_SET_TYPE(le, arc_flags_to_bufc(ab->b_flags));
9211 dev->l2ad_log_blk_payload_asize += arc_hdr_size((arc_buf_hdr_t *)ab);
9212
9213 return (dev->l2ad_log_ent_idx == L2ARC_LOG_BLK_ENTRIES);
9214 }
9215
9216 /*
9217 * Checks whether a given L2ARC device address sits in a time-sequential
9218 * range. The trick here is that the L2ARC is a rotary buffer, so we can't
9219 * just do a range comparison, we need to handle the situation in which the
9220 * range wraps around the end of the L2ARC device. Arguments:
9221 * bottom Lower end of the range to check (written to earlier).
9222 * top Upper end of the range to check (written to later).
9223 * check The address for which we want to determine if it sits in
9224 * between the top and bottom.
9225 *
9226 * The 3-way conditional below represents the following cases:
9227 *
9228 * bottom < top : Sequentially ordered case:
9229 * <check>--------+-------------------+
9230 * | (overlap here?) |
9231 * L2ARC dev V V
9232 * |---------------<bottom>============<top>--------------|
9233 *
9234 * bottom > top: Looped-around case:
9235 * <check>--------+------------------+
9236 * | (overlap here?) |
9237 * L2ARC dev V V
9238 * |===============<top>---------------<bottom>===========|
9239 * ^ ^
9240 * | (or here?) |
9241 * +---------------+---------<check>
9242 *
9243 * top == bottom : Just a single address comparison.
9244 */
9245 static inline boolean_t
9246 l2arc_range_check_overlap(uint64_t bottom, uint64_t top, uint64_t check)
9247 {
9248 if (bottom < top)
9249 return (bottom <= check && check <= top);
9250 else if (bottom > top)
9251 return (check <= top || bottom <= check);
9252 else
9253 return (check == top);
9254 }