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 /*
23 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
24 * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
25 * Copyright 2016 Nexenta Systems, Inc. All rights reserved.
26 */
27
28 /*
29 * Virtual Device Labels
30 * ---------------------
31 *
32 * The vdev label serves several distinct purposes:
33 *
34 * 1. Uniquely identify this device as part of a ZFS pool and confirm its
35 * identity within the pool.
36 *
37 * 2. Verify that all the devices given in a configuration are present
38 * within the pool.
39 *
40 * 3. Determine the uberblock for the pool.
41 *
42 * 4. In case of an import operation, determine the configuration of the
43 * toplevel vdev of which it is a part.
44 *
45 * 5. If an import operation cannot find all the devices in the pool,
46 * provide enough information to the administrator to determine which
47 * devices are missing.
48 *
49 * It is important to note that while the kernel is responsible for writing the
50 * label, it only consumes the information in the first three cases. The
51 * latter information is only consumed in userland when determining the
52 * configuration to import a pool.
53 *
54 *
55 * Label Organization
56 * ------------------
57 *
58 * Before describing the contents of the label, it's important to understand how
59 * the labels are written and updated with respect to the uberblock.
60 *
61 * When the pool configuration is altered, either because it was newly created
62 * or a device was added, we want to update all the labels such that we can deal
63 * with fatal failure at any point. To this end, each disk has two labels which
64 * are updated before and after the uberblock is synced. Assuming we have
65 * labels and an uberblock with the following transaction groups:
66 *
67 * L1 UB L2
68 * +------+ +------+ +------+
69 * | | | | | |
70 * | t10 | | t10 | | t10 |
71 * | | | | | |
72 * +------+ +------+ +------+
73 *
74 * In this stable state, the labels and the uberblock were all updated within
75 * the same transaction group (10). Each label is mirrored and checksummed, so
76 * that we can detect when we fail partway through writing the label.
77 *
78 * In order to identify which labels are valid, the labels are written in the
79 * following manner:
80 *
81 * 1. For each vdev, update 'L1' to the new label
82 * 2. Update the uberblock
83 * 3. For each vdev, update 'L2' to the new label
84 *
85 * Given arbitrary failure, we can determine the correct label to use based on
86 * the transaction group. If we fail after updating L1 but before updating the
87 * UB, we will notice that L1's transaction group is greater than the uberblock,
88 * so L2 must be valid. If we fail after writing the uberblock but before
89 * writing L2, we will notice that L2's transaction group is less than L1, and
90 * therefore L1 is valid.
91 *
92 * Another added complexity is that not every label is updated when the config
93 * is synced. If we add a single device, we do not want to have to re-write
94 * every label for every device in the pool. This means that both L1 and L2 may
95 * be older than the pool uberblock, because the necessary information is stored
96 * on another vdev.
97 *
98 *
99 * On-disk Format
100 * --------------
101 *
102 * The vdev label consists of two distinct parts, and is wrapped within the
103 * vdev_label_t structure. The label includes 8k of padding to permit legacy
104 * VTOC disk labels, but is otherwise ignored.
105 *
106 * The first half of the label is a packed nvlist which contains pool wide
107 * properties, per-vdev properties, and configuration information. It is
108 * described in more detail below.
109 *
110 * The latter half of the label consists of a redundant array of uberblocks.
111 * These uberblocks are updated whenever a transaction group is committed,
112 * or when the configuration is updated. When a pool is loaded, we scan each
113 * vdev for the 'best' uberblock.
114 *
115 *
116 * Configuration Information
117 * -------------------------
118 *
119 * The nvlist describing the pool and vdev contains the following elements:
120 *
121 * version ZFS on-disk version
122 * name Pool name
123 * state Pool state
124 * txg Transaction group in which this label was written
125 * pool_guid Unique identifier for this pool
126 * vdev_tree An nvlist describing vdev tree.
127 * features_for_read
128 * An nvlist of the features necessary for reading the MOS.
129 *
130 * Each leaf device label also contains the following:
131 *
132 * top_guid Unique ID for top-level vdev in which this is contained
133 * guid Unique ID for the leaf vdev
134 *
135 * The 'vs' configuration follows the format described in 'spa_config.c'.
136 */
137
138 #include <sys/zfs_context.h>
139 #include <sys/spa.h>
140 #include <sys/spa_impl.h>
141 #include <sys/dmu.h>
142 #include <sys/zap.h>
143 #include <sys/vdev.h>
144 #include <sys/vdev_impl.h>
145 #include <sys/uberblock_impl.h>
146 #include <sys/metaslab.h>
147 #include <sys/zio.h>
148 #include <sys/dsl_scan.h>
149 #include <sys/abd.h>
150 #include <sys/fs/zfs.h>
151
152 /*
153 * Basic routines to read and write from a vdev label.
154 * Used throughout the rest of this file.
155 */
156 uint64_t
157 vdev_label_offset(uint64_t psize, int l, uint64_t offset)
158 {
159 ASSERT(offset < sizeof (vdev_label_t));
160 ASSERT(P2PHASE_TYPED(psize, sizeof (vdev_label_t), uint64_t) == 0);
161
162 return (offset + l * sizeof (vdev_label_t) + (l < VDEV_LABELS / 2 ?
163 0 : psize - VDEV_LABELS * sizeof (vdev_label_t)));
164 }
165
166 /*
167 * Returns back the vdev label associated with the passed in offset.
168 */
169 int
170 vdev_label_number(uint64_t psize, uint64_t offset)
171 {
172 int l;
173
174 if (offset >= psize - VDEV_LABEL_END_SIZE) {
175 offset -= psize - VDEV_LABEL_END_SIZE;
176 offset += (VDEV_LABELS / 2) * sizeof (vdev_label_t);
177 }
178 l = offset / sizeof (vdev_label_t);
179 return (l < VDEV_LABELS ? l : -1);
180 }
181
182 static void
183 vdev_label_read(zio_t *zio, vdev_t *vd, int l, abd_t *buf, uint64_t offset,
184 uint64_t size, zio_done_func_t *done, void *private, int flags)
185 {
186 ASSERT(spa_config_held(zio->io_spa, SCL_STATE_ALL, RW_WRITER) ==
187 SCL_STATE_ALL);
188 ASSERT(flags & ZIO_FLAG_CONFIG_WRITER);
189
190 zio_nowait(zio_read_phys(zio, vd,
191 vdev_label_offset(vd->vdev_psize, l, offset),
192 size, buf, ZIO_CHECKSUM_LABEL, done, private,
193 ZIO_PRIORITY_SYNC_READ, flags, B_TRUE));
194 }
195
196 static void
197 vdev_label_write(zio_t *zio, vdev_t *vd, int l, abd_t *buf, uint64_t offset,
198 uint64_t size, zio_done_func_t *done, void *private, int flags)
199 {
200 ASSERT(spa_config_held(zio->io_spa, SCL_ALL, RW_WRITER) == SCL_ALL ||
201 (spa_config_held(zio->io_spa, SCL_CONFIG | SCL_STATE, RW_READER) ==
202 (SCL_CONFIG | SCL_STATE) &&
203 dsl_pool_sync_context(spa_get_dsl(zio->io_spa))));
204 ASSERT(flags & ZIO_FLAG_CONFIG_WRITER);
205
206 zio_nowait(zio_write_phys(zio, vd,
207 vdev_label_offset(vd->vdev_psize, l, offset),
208 size, buf, ZIO_CHECKSUM_LABEL, done, private,
209 ZIO_PRIORITY_SYNC_WRITE, flags, B_TRUE));
210 }
211
212 /*
213 * Generate the nvlist representing this vdev's config.
214 */
215 nvlist_t *
216 vdev_config_generate(spa_t *spa, vdev_t *vd, boolean_t getstats,
217 vdev_config_flag_t flags)
218 {
219 nvlist_t *nv = NULL;
220
221 nv = fnvlist_alloc();
222
223 fnvlist_add_string(nv, ZPOOL_CONFIG_TYPE, vd->vdev_ops->vdev_op_type);
224 if (!(flags & (VDEV_CONFIG_SPARE | VDEV_CONFIG_L2CACHE)))
225 fnvlist_add_uint64(nv, ZPOOL_CONFIG_ID, vd->vdev_id);
226 fnvlist_add_uint64(nv, ZPOOL_CONFIG_GUID, vd->vdev_guid);
227
228 if (vd->vdev_path != NULL)
229 fnvlist_add_string(nv, ZPOOL_CONFIG_PATH, vd->vdev_path);
230
231 if (vd->vdev_devid != NULL)
232 fnvlist_add_string(nv, ZPOOL_CONFIG_DEVID, vd->vdev_devid);
233
234 if (vd->vdev_physpath != NULL)
235 fnvlist_add_string(nv, ZPOOL_CONFIG_PHYS_PATH,
236 vd->vdev_physpath);
237
238 if (vd->vdev_fru != NULL)
239 fnvlist_add_string(nv, ZPOOL_CONFIG_FRU, vd->vdev_fru);
240
241 if (vd->vdev_nparity != 0) {
242 ASSERT(strcmp(vd->vdev_ops->vdev_op_type,
243 VDEV_TYPE_RAIDZ) == 0);
244
245 /*
246 * Make sure someone hasn't managed to sneak a fancy new vdev
247 * into a crufty old storage pool.
248 */
249 ASSERT(vd->vdev_nparity == 1 ||
250 (vd->vdev_nparity <= 2 &&
251 spa_version(spa) >= SPA_VERSION_RAIDZ2) ||
252 (vd->vdev_nparity <= 3 &&
253 spa_version(spa) >= SPA_VERSION_RAIDZ3));
254
255 /*
256 * Note that we'll add the nparity tag even on storage pools
257 * that only support a single parity device -- older software
258 * will just ignore it.
259 */
260 fnvlist_add_uint64(nv, ZPOOL_CONFIG_NPARITY, vd->vdev_nparity);
261 }
262
263 if (vd->vdev_wholedisk != -1ULL)
264 fnvlist_add_uint64(nv, ZPOOL_CONFIG_WHOLE_DISK,
265 vd->vdev_wholedisk);
266
267 if (vd->vdev_not_present)
268 fnvlist_add_uint64(nv, ZPOOL_CONFIG_NOT_PRESENT, 1);
269
270 if (vd->vdev_isspare)
271 fnvlist_add_uint64(nv, ZPOOL_CONFIG_IS_SPARE, 1);
272
273 if (!(flags & (VDEV_CONFIG_SPARE | VDEV_CONFIG_L2CACHE)) &&
274 vd == vd->vdev_top) {
275 fnvlist_add_uint64(nv, ZPOOL_CONFIG_METASLAB_ARRAY,
276 vd->vdev_ms_array);
277 fnvlist_add_uint64(nv, ZPOOL_CONFIG_METASLAB_SHIFT,
278 vd->vdev_ms_shift);
279 fnvlist_add_uint64(nv, ZPOOL_CONFIG_ASHIFT, vd->vdev_ashift);
280 fnvlist_add_uint64(nv, ZPOOL_CONFIG_ASIZE,
281 vd->vdev_asize);
282 fnvlist_add_uint64(nv, ZPOOL_CONFIG_IS_LOG, vd->vdev_islog);
283 fnvlist_add_uint64(nv, ZPOOL_CONFIG_IS_SPECIAL,
284 vd->vdev_isspecial);
285 if (vd->vdev_removing)
286 fnvlist_add_uint64(nv, ZPOOL_CONFIG_REMOVING,
287 vd->vdev_removing);
288 }
289
290 if (flags & VDEV_CONFIG_L2CACHE)
291 /* indicate that we support L2ARC persistency */
292 VERIFY(nvlist_add_boolean_value(nv,
293 ZPOOL_CONFIG_L2CACHE_PERSISTENT, B_TRUE) == 0);
294
295 fnvlist_add_boolean_value(nv, ZPOOL_CONFIG_IS_SSD, vd->vdev_is_ssd);
296
297 if (vd->vdev_dtl_sm != NULL) {
298 fnvlist_add_uint64(nv, ZPOOL_CONFIG_DTL,
299 space_map_object(vd->vdev_dtl_sm));
300 }
301
302 if (vd->vdev_crtxg)
303 fnvlist_add_uint64(nv, ZPOOL_CONFIG_CREATE_TXG, vd->vdev_crtxg);
304
305 if (flags & VDEV_CONFIG_MOS) {
306 if (vd->vdev_leaf_zap != 0) {
307 ASSERT(vd->vdev_ops->vdev_op_leaf);
308 fnvlist_add_uint64(nv, ZPOOL_CONFIG_VDEV_LEAF_ZAP,
309 vd->vdev_leaf_zap);
310 }
311
312 if (vd->vdev_top_zap != 0) {
313 ASSERT(vd == vd->vdev_top);
314 fnvlist_add_uint64(nv, ZPOOL_CONFIG_VDEV_TOP_ZAP,
315 vd->vdev_top_zap);
316 }
317 }
318
319 if (getstats) {
320 vdev_stat_t vs;
321 pool_scan_stat_t ps;
322
323 vdev_get_stats(vd, &vs);
324 fnvlist_add_uint64_array(nv, ZPOOL_CONFIG_VDEV_STATS,
325 (uint64_t *)&vs, sizeof (vs) / sizeof (uint64_t));
326
327 /* provide either current or previous scan information */
328 if (spa_scan_get_stats(spa, &ps) == 0) {
329 fnvlist_add_uint64_array(nv,
330 ZPOOL_CONFIG_SCAN_STATS, (uint64_t *)&ps,
331 sizeof (pool_scan_stat_t) / sizeof (uint64_t));
332 }
333 }
334
335 if (!vd->vdev_ops->vdev_op_leaf) {
336 nvlist_t **child;
337 int c, idx;
338
339 ASSERT(!vd->vdev_ishole);
340
341 child = kmem_alloc(vd->vdev_children * sizeof (nvlist_t *),
342 KM_SLEEP);
343
344 for (c = 0, idx = 0; c < vd->vdev_children; c++) {
345 vdev_t *cvd = vd->vdev_child[c];
346
347 /*
348 * If we're generating an nvlist of removing
349 * vdevs then skip over any device which is
350 * not being removed.
351 */
352 if ((flags & VDEV_CONFIG_REMOVING) &&
353 !cvd->vdev_removing)
354 continue;
355
356 child[idx++] = vdev_config_generate(spa, cvd,
357 getstats, flags);
358 }
359
360 if (idx) {
361 fnvlist_add_nvlist_array(nv, ZPOOL_CONFIG_CHILDREN,
362 child, idx);
363 }
364
365 for (c = 0; c < idx; c++)
366 nvlist_free(child[c]);
367
368 kmem_free(child, vd->vdev_children * sizeof (nvlist_t *));
369
370 } else {
371 const char *aux = NULL;
372
373 if (vd->vdev_offline && !vd->vdev_tmpoffline)
374 fnvlist_add_uint64(nv, ZPOOL_CONFIG_OFFLINE, B_TRUE);
375 if (vd->vdev_resilver_txg != 0)
376 fnvlist_add_uint64(nv, ZPOOL_CONFIG_RESILVER_TXG,
377 vd->vdev_resilver_txg);
378 if (vd->vdev_faulted)
379 fnvlist_add_uint64(nv, ZPOOL_CONFIG_FAULTED, B_TRUE);
380 if (vd->vdev_degraded)
381 fnvlist_add_uint64(nv, ZPOOL_CONFIG_DEGRADED, B_TRUE);
382 if (vd->vdev_removed)
383 fnvlist_add_uint64(nv, ZPOOL_CONFIG_REMOVED, B_TRUE);
384 if (vd->vdev_unspare)
385 fnvlist_add_uint64(nv, ZPOOL_CONFIG_UNSPARE, B_TRUE);
386 if (vd->vdev_ishole)
387 fnvlist_add_uint64(nv, ZPOOL_CONFIG_IS_HOLE, B_TRUE);
388
389 switch (vd->vdev_stat.vs_aux) {
390 case VDEV_AUX_ERR_EXCEEDED:
391 aux = "err_exceeded";
392 break;
393
394 case VDEV_AUX_EXTERNAL:
395 aux = "external";
396 break;
397 }
398
399 if (aux != NULL)
400 fnvlist_add_string(nv, ZPOOL_CONFIG_AUX_STATE, aux);
401
402 if (vd->vdev_splitting && vd->vdev_orig_guid != 0LL) {
403 fnvlist_add_uint64(nv, ZPOOL_CONFIG_ORIG_GUID,
404 vd->vdev_orig_guid);
405 }
406
407 /* grab per-leaf-vdev trim stats */
408 if (getstats) {
409 fnvlist_add_uint64(nv, ZPOOL_CONFIG_TRIM_PROG,
410 vd->vdev_trim_prog);
411 }
412 }
413
414 return (nv);
415 }
416
417 /*
418 * Generate a view of the top-level vdevs. If we currently have holes
419 * in the namespace, then generate an array which contains a list of holey
420 * vdevs. Additionally, add the number of top-level children that currently
421 * exist.
422 */
423 void
424 vdev_top_config_generate(spa_t *spa, nvlist_t *config)
425 {
426 vdev_t *rvd = spa->spa_root_vdev;
427 uint64_t *array;
428 uint_t c, idx;
429
430 array = kmem_alloc(rvd->vdev_children * sizeof (uint64_t), KM_SLEEP);
431
432 for (c = 0, idx = 0; c < rvd->vdev_children; c++) {
433 vdev_t *tvd = rvd->vdev_child[c];
434
435 if (tvd->vdev_ishole)
436 array[idx++] = c;
437 }
438
439 if (idx) {
440 VERIFY(nvlist_add_uint64_array(config, ZPOOL_CONFIG_HOLE_ARRAY,
441 array, idx) == 0);
442 }
443
444 VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_VDEV_CHILDREN,
445 rvd->vdev_children) == 0);
446
447 kmem_free(array, rvd->vdev_children * sizeof (uint64_t));
448 }
449
450 /*
451 * Returns the configuration from the label of the given vdev. For vdevs
452 * which don't have a txg value stored on their label (i.e. spares/cache)
453 * or have not been completely initialized (txg = 0) just return
454 * the configuration from the first valid label we find. Otherwise,
455 * find the most up-to-date label that does not exceed the specified
456 * 'txg' value.
457 */
458 nvlist_t *
459 vdev_label_read_config(vdev_t *vd, uint64_t txg)
460 {
461 spa_t *spa = vd->vdev_spa;
462 nvlist_t *config = NULL;
463 vdev_phys_t *vp;
464 abd_t *vp_abd;
465 zio_t *zio;
466 uint64_t best_txg = 0;
467 int error = 0;
468 int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL |
469 ZIO_FLAG_SPECULATIVE;
470
471 ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
472
473 if (!vdev_readable(vd))
474 return (NULL);
475
476 vp_abd = abd_alloc_linear(sizeof (vdev_phys_t), B_TRUE);
477 vp = abd_to_buf(vp_abd);
478
479 retry:
480 for (int l = 0; l < VDEV_LABELS; l++) {
481 nvlist_t *label = NULL;
482
483 zio = zio_root(spa, NULL, NULL, flags);
484
485 vdev_label_read(zio, vd, l, vp_abd,
486 offsetof(vdev_label_t, vl_vdev_phys),
487 sizeof (vdev_phys_t), NULL, NULL, flags);
488
489 if (zio_wait(zio) == 0 &&
490 nvlist_unpack(vp->vp_nvlist, sizeof (vp->vp_nvlist),
491 &label, 0) == 0) {
492 uint64_t label_txg = 0;
493
494 /*
495 * Auxiliary vdevs won't have txg values in their
496 * labels and newly added vdevs may not have been
497 * completely initialized so just return the
498 * configuration from the first valid label we
499 * encounter.
500 */
501 error = nvlist_lookup_uint64(label,
502 ZPOOL_CONFIG_POOL_TXG, &label_txg);
503 if ((error || label_txg == 0) && !config) {
504 config = label;
505 break;
506 } else if (label_txg <= txg && label_txg > best_txg) {
507 best_txg = label_txg;
508 nvlist_free(config);
509 config = fnvlist_dup(label);
510 }
511 }
512
513 if (label != NULL) {
514 nvlist_free(label);
515 label = NULL;
516 }
517 }
518
519 if (config == NULL && !(flags & ZIO_FLAG_TRYHARD)) {
520 flags |= ZIO_FLAG_TRYHARD;
521 goto retry;
522 }
523
524 abd_free(vp_abd);
525
526 return (config);
527 }
528
529 /*
530 * Determine if a device is in use. The 'spare_guid' parameter will be filled
531 * in with the device guid if this spare is active elsewhere on the system.
532 */
533 static boolean_t
534 vdev_inuse(vdev_t *vd, uint64_t crtxg, vdev_labeltype_t reason,
535 uint64_t *spare_guid, uint64_t *l2cache_guid)
536 {
537 spa_t *spa = vd->vdev_spa;
538 uint64_t state, pool_guid, device_guid, txg, spare_pool;
539 uint64_t vdtxg = 0;
540 nvlist_t *label;
541
542 if (spare_guid)
543 *spare_guid = 0ULL;
544 if (l2cache_guid)
545 *l2cache_guid = 0ULL;
546
547 /*
548 * Read the label, if any, and perform some basic sanity checks.
549 */
550 if ((label = vdev_label_read_config(vd, -1ULL)) == NULL)
551 return (B_FALSE);
552
553 (void) nvlist_lookup_uint64(label, ZPOOL_CONFIG_CREATE_TXG,
554 &vdtxg);
555
556 if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE,
557 &state) != 0 ||
558 nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID,
559 &device_guid) != 0) {
560 nvlist_free(label);
561 return (B_FALSE);
562 }
563
564 if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
565 (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID,
566 &pool_guid) != 0 ||
567 nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_TXG,
568 &txg) != 0)) {
569 nvlist_free(label);
570 return (B_FALSE);
571 }
572
573 nvlist_free(label);
574
575 /*
576 * Check to see if this device indeed belongs to the pool it claims to
577 * be a part of. The only way this is allowed is if the device is a hot
578 * spare (which we check for later on).
579 */
580 if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
581 !spa_guid_exists(pool_guid, device_guid) &&
582 !spa_spare_exists(device_guid, NULL, NULL) &&
583 !spa_l2cache_exists(device_guid, NULL))
584 return (B_FALSE);
585
586 /*
587 * If the transaction group is zero, then this an initialized (but
588 * unused) label. This is only an error if the create transaction
589 * on-disk is the same as the one we're using now, in which case the
590 * user has attempted to add the same vdev multiple times in the same
591 * transaction.
592 */
593 if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
594 txg == 0 && vdtxg == crtxg)
595 return (B_TRUE);
596
597 /*
598 * Check to see if this is a spare device. We do an explicit check for
599 * spa_has_spare() here because it may be on our pending list of spares
600 * to add. We also check if it is an l2cache device.
601 */
602 if (spa_spare_exists(device_guid, &spare_pool, NULL) ||
603 spa_has_spare(spa, device_guid)) {
604 if (spare_guid)
605 *spare_guid = device_guid;
606
607 switch (reason) {
608 case VDEV_LABEL_CREATE:
609 case VDEV_LABEL_L2CACHE:
610 return (B_TRUE);
611
612 case VDEV_LABEL_REPLACE:
613 return (!spa_has_spare(spa, device_guid) ||
614 spare_pool != 0ULL);
615
616 case VDEV_LABEL_SPARE:
617 return (spa_has_spare(spa, device_guid));
618 }
619 }
620
621 /*
622 * Check to see if this is an l2cache device.
623 */
624 if (spa_l2cache_exists(device_guid, NULL))
625 return (B_TRUE);
626
627 /*
628 * We can't rely on a pool's state if it's been imported
629 * read-only. Instead we look to see if the pools is marked
630 * read-only in the namespace and set the state to active.
631 */
632 if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
633 (spa = spa_by_guid(pool_guid, device_guid)) != NULL &&
634 spa_mode(spa) == FREAD)
635 state = POOL_STATE_ACTIVE;
636
637 /*
638 * If the device is marked ACTIVE, then this device is in use by another
639 * pool on the system.
640 */
641 return (state == POOL_STATE_ACTIVE);
642 }
643
644 /*
645 * Initialize a vdev label. We check to make sure each leaf device is not in
646 * use, and writable. We put down an initial label which we will later
647 * overwrite with a complete label. Note that it's important to do this
648 * sequentially, not in parallel, so that we catch cases of multiple use of the
649 * same leaf vdev in the vdev we're creating -- e.g. mirroring a disk with
650 * itself.
651 */
652 int
653 vdev_label_init(vdev_t *vd, uint64_t crtxg, vdev_labeltype_t reason)
654 {
655 spa_t *spa = vd->vdev_spa;
656 nvlist_t *label;
657 vdev_phys_t *vp;
658 abd_t *vp_abd;
659 abd_t *pad2;
660 uberblock_t *ub;
661 abd_t *ub_abd;
662 zio_t *zio;
663 char *buf;
664 size_t buflen;
665 int error;
666 uint64_t spare_guid, l2cache_guid;
667 int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL;
668
669 ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
670
671 for (int c = 0; c < vd->vdev_children; c++)
672 if ((error = vdev_label_init(vd->vdev_child[c],
673 crtxg, reason)) != 0)
674 return (error);
675
676 /* Track the creation time for this vdev */
677 vd->vdev_crtxg = crtxg;
678
679 if (!vd->vdev_ops->vdev_op_leaf || !spa_writeable(spa))
680 return (0);
681
682 /*
683 * Dead vdevs cannot be initialized.
684 */
685 if (vdev_is_dead(vd))
686 return (SET_ERROR(EIO));
687
688 /*
689 * Determine if the vdev is in use.
690 */
691 if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_SPLIT &&
692 vdev_inuse(vd, crtxg, reason, &spare_guid, &l2cache_guid))
693 return (SET_ERROR(EBUSY));
694
695 /*
696 * If this is a request to add or replace a spare or l2cache device
697 * that is in use elsewhere on the system, then we must update the
698 * guid (which was initialized to a random value) to reflect the
699 * actual GUID (which is shared between multiple pools).
700 */
701 if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_L2CACHE &&
702 spare_guid != 0ULL) {
703 uint64_t guid_delta = spare_guid - vd->vdev_guid;
704
705 vd->vdev_guid += guid_delta;
706
707 for (vdev_t *pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
708 pvd->vdev_guid_sum += guid_delta;
709
710 /*
711 * If this is a replacement, then we want to fallthrough to the
712 * rest of the code. If we're adding a spare, then it's already
713 * labeled appropriately and we can just return.
714 */
715 if (reason == VDEV_LABEL_SPARE)
716 return (0);
717 ASSERT(reason == VDEV_LABEL_REPLACE ||
718 reason == VDEV_LABEL_SPLIT);
719 }
720
721 if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_SPARE &&
722 l2cache_guid != 0ULL) {
723 uint64_t guid_delta = l2cache_guid - vd->vdev_guid;
724
725 vd->vdev_guid += guid_delta;
726
727 for (vdev_t *pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
728 pvd->vdev_guid_sum += guid_delta;
729
730 /*
731 * If this is a replacement, then we want to fallthrough to the
732 * rest of the code. If we're adding an l2cache, then it's
733 * already labeled appropriately and we can just return.
734 */
735 if (reason == VDEV_LABEL_L2CACHE)
736 return (0);
737 ASSERT(reason == VDEV_LABEL_REPLACE);
738 }
739
740 /*
741 * Initialize its label.
742 */
743 vp_abd = abd_alloc_linear(sizeof (vdev_phys_t), B_TRUE);
744 abd_zero(vp_abd, sizeof (vdev_phys_t));
745 vp = abd_to_buf(vp_abd);
746
747 /*
748 * Generate a label describing the pool and our top-level vdev.
749 * We mark it as being from txg 0 to indicate that it's not
750 * really part of an active pool just yet. The labels will
751 * be written again with a meaningful txg by spa_sync().
752 */
753 if (reason == VDEV_LABEL_SPARE ||
754 (reason == VDEV_LABEL_REMOVE && vd->vdev_isspare)) {
755 /*
756 * For inactive hot spares, we generate a special label that
757 * identifies as a mutually shared hot spare. We write the
758 * label if we are adding a hot spare, or if we are removing an
759 * active hot spare (in which case we want to revert the
760 * labels).
761 */
762 VERIFY(nvlist_alloc(&label, NV_UNIQUE_NAME, KM_SLEEP) == 0);
763
764 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_VERSION,
765 spa_version(spa)) == 0);
766 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_POOL_STATE,
767 POOL_STATE_SPARE) == 0);
768 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_GUID,
769 vd->vdev_guid) == 0);
770 } else if (reason == VDEV_LABEL_L2CACHE ||
771 (reason == VDEV_LABEL_REMOVE && vd->vdev_isl2cache)) {
772 /*
773 * For level 2 ARC devices, add a special label.
774 */
775 VERIFY(nvlist_alloc(&label, NV_UNIQUE_NAME, KM_SLEEP) == 0);
776
777 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_VERSION,
778 spa_version(spa)) == 0);
779 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_POOL_STATE,
780 POOL_STATE_L2CACHE) == 0);
781 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_GUID,
782 vd->vdev_guid) == 0);
783 } else {
784 uint64_t txg = 0ULL;
785
786 if (reason == VDEV_LABEL_SPLIT)
787 txg = spa->spa_uberblock.ub_txg;
788 label = spa_config_generate(spa, vd, txg, B_FALSE);
789
790 /*
791 * Add our creation time. This allows us to detect multiple
792 * vdev uses as described above, and automatically expires if we
793 * fail.
794 */
795 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_CREATE_TXG,
796 crtxg) == 0);
797 }
798
799 buf = vp->vp_nvlist;
800 buflen = sizeof (vp->vp_nvlist);
801
802 error = nvlist_pack(label, &buf, &buflen, NV_ENCODE_XDR, KM_SLEEP);
803 if (error != 0) {
804 nvlist_free(label);
805 abd_free(vp_abd);
806 /* EFAULT means nvlist_pack ran out of room */
807 return (error == EFAULT ? ENAMETOOLONG : EINVAL);
808 }
809
810 /*
811 * Initialize uberblock template.
812 */
813 ub_abd = abd_alloc_linear(VDEV_UBERBLOCK_RING, B_TRUE);
814 abd_zero(ub_abd, VDEV_UBERBLOCK_RING);
815 abd_copy_from_buf(ub_abd, &spa->spa_uberblock, sizeof (uberblock_t));
816 ub = abd_to_buf(ub_abd);
817 ub->ub_txg = 0;
818
819 /* Initialize the 2nd padding area. */
820 pad2 = abd_alloc_for_io(VDEV_PAD_SIZE, B_TRUE);
821 abd_zero(pad2, VDEV_PAD_SIZE);
822
823 /*
824 * Write everything in parallel.
825 */
826 retry:
827 zio = zio_root(spa, NULL, NULL, flags);
828
829 for (int l = 0; l < VDEV_LABELS; l++) {
830
831 vdev_label_write(zio, vd, l, vp_abd,
832 offsetof(vdev_label_t, vl_vdev_phys),
833 sizeof (vdev_phys_t), NULL, NULL, flags);
834
835 /*
836 * Skip the 1st padding area.
837 * Zero out the 2nd padding area where it might have
838 * left over data from previous filesystem format.
839 */
840 vdev_label_write(zio, vd, l, pad2,
841 offsetof(vdev_label_t, vl_pad2),
842 VDEV_PAD_SIZE, NULL, NULL, flags);
843
844 vdev_label_write(zio, vd, l, ub_abd,
845 offsetof(vdev_label_t, vl_uberblock),
846 VDEV_UBERBLOCK_RING, NULL, NULL, flags);
847 }
848
849 error = zio_wait(zio);
850
851 if (error != 0 && !(flags & ZIO_FLAG_TRYHARD)) {
852 flags |= ZIO_FLAG_TRYHARD;
853 goto retry;
854 }
855
856 nvlist_free(label);
857 abd_free(pad2);
858 abd_free(ub_abd);
859 abd_free(vp_abd);
860
861 /*
862 * If this vdev hasn't been previously identified as a spare, then we
863 * mark it as such only if a) we are labeling it as a spare, or b) it
864 * exists as a spare elsewhere in the system. Do the same for
865 * level 2 ARC devices.
866 */
867 if (error == 0 && !vd->vdev_isspare &&
868 (reason == VDEV_LABEL_SPARE ||
869 spa_spare_exists(vd->vdev_guid, NULL, NULL)))
870 spa_spare_add(vd);
871
872 if (error == 0 && !vd->vdev_isl2cache &&
873 (reason == VDEV_LABEL_L2CACHE ||
874 spa_l2cache_exists(vd->vdev_guid, NULL)))
875 spa_l2cache_add(vd);
876
877 return (error);
878 }
879
880 /*
881 * ==========================================================================
882 * uberblock load/sync
883 * ==========================================================================
884 */
885
886 /*
887 * Consider the following situation: txg is safely synced to disk. We've
888 * written the first uberblock for txg + 1, and then we lose power. When we
889 * come back up, we fail to see the uberblock for txg + 1 because, say,
890 * it was on a mirrored device and the replica to which we wrote txg + 1
891 * is now offline. If we then make some changes and sync txg + 1, and then
892 * the missing replica comes back, then for a few seconds we'll have two
893 * conflicting uberblocks on disk with the same txg. The solution is simple:
894 * among uberblocks with equal txg, choose the one with the latest timestamp.
895 */
896 static int
897 vdev_uberblock_compare(uberblock_t *ub1, uberblock_t *ub2)
898 {
899 if (ub1->ub_txg < ub2->ub_txg)
900 return (-1);
901 if (ub1->ub_txg > ub2->ub_txg)
902 return (1);
903
904 if (ub1->ub_timestamp < ub2->ub_timestamp)
905 return (-1);
906 if (ub1->ub_timestamp > ub2->ub_timestamp)
907 return (1);
908
909 return (0);
910 }
911
912 struct ubl_cbdata {
913 uberblock_t *ubl_ubbest; /* Best uberblock */
914 vdev_t *ubl_vd; /* vdev associated with the above */
915 };
916
917 static void
918 vdev_uberblock_load_done(zio_t *zio)
919 {
920 vdev_t *vd = zio->io_vd;
921 spa_t *spa = zio->io_spa;
922 zio_t *rio = zio->io_private;
923 uberblock_t *ub = abd_to_buf(zio->io_abd);
924 struct ubl_cbdata *cbp = rio->io_private;
925
926 ASSERT3U(zio->io_size, ==, VDEV_UBERBLOCK_SIZE(vd));
927
928 if (zio->io_error == 0 && uberblock_verify(ub) == 0) {
929 mutex_enter(&rio->io_lock);
930 if (ub->ub_txg <= spa->spa_load_max_txg &&
931 vdev_uberblock_compare(ub, cbp->ubl_ubbest) > 0) {
932 /*
933 * Keep track of the vdev in which this uberblock
934 * was found. We will use this information later
935 * to obtain the config nvlist associated with
936 * this uberblock.
937 */
938 *cbp->ubl_ubbest = *ub;
939 cbp->ubl_vd = vd;
940 }
941 mutex_exit(&rio->io_lock);
942 }
943
944 abd_free(zio->io_abd);
945 }
946
947 static void
948 vdev_uberblock_load_impl(zio_t *zio, vdev_t *vd, int flags,
949 struct ubl_cbdata *cbp)
950 {
951 for (int c = 0; c < vd->vdev_children; c++)
952 vdev_uberblock_load_impl(zio, vd->vdev_child[c], flags, cbp);
953
954 if (vd->vdev_ops->vdev_op_leaf && vdev_readable(vd)) {
955 for (int l = 0; l < VDEV_LABELS; l++) {
956 for (int n = 0; n < VDEV_UBERBLOCK_COUNT(vd); n++) {
957 vdev_label_read(zio, vd, l,
958 abd_alloc_linear(VDEV_UBERBLOCK_SIZE(vd),
959 B_TRUE), VDEV_UBERBLOCK_OFFSET(vd, n),
960 VDEV_UBERBLOCK_SIZE(vd),
961 vdev_uberblock_load_done, zio, flags);
962 }
963 }
964 }
965 }
966
967 /*
968 * Reads the 'best' uberblock from disk along with its associated
969 * configuration. First, we read the uberblock array of each label of each
970 * vdev, keeping track of the uberblock with the highest txg in each array.
971 * Then, we read the configuration from the same vdev as the best uberblock.
972 */
973 void
974 vdev_uberblock_load(vdev_t *rvd, uberblock_t *ub, nvlist_t **config)
975 {
976 zio_t *zio;
977 spa_t *spa = rvd->vdev_spa;
978 struct ubl_cbdata cb;
979 int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL |
980 ZIO_FLAG_SPECULATIVE | ZIO_FLAG_TRYHARD;
981
982 ASSERT(ub);
983 ASSERT(config);
984
985 bzero(ub, sizeof (uberblock_t));
986 *config = NULL;
987
988 cb.ubl_ubbest = ub;
989 cb.ubl_vd = NULL;
990
991 spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
992 zio = zio_root(spa, NULL, &cb, flags);
993 vdev_uberblock_load_impl(zio, rvd, flags, &cb);
994 (void) zio_wait(zio);
995
996 /*
997 * It's possible that the best uberblock was discovered on a label
998 * that has a configuration which was written in a future txg.
999 * Search all labels on this vdev to find the configuration that
1000 * matches the txg for our uberblock.
1001 */
1002 if (cb.ubl_vd != NULL)
1003 *config = vdev_label_read_config(cb.ubl_vd, ub->ub_txg);
1004 spa_config_exit(spa, SCL_ALL, FTAG);
1005 }
1006
1007 /*
1008 * On success, increment root zio's count of good writes.
1009 * We only get credit for writes to known-visible vdevs; see spa_vdev_add().
1010 */
1011 static void
1012 vdev_uberblock_sync_done(zio_t *zio)
1013 {
1014 uint64_t *good_writes = zio->io_private;
1015
1016 if (zio->io_error == 0 && zio->io_vd->vdev_top->vdev_ms_array != 0)
1017 atomic_inc_64(good_writes);
1018 }
1019
1020 /*
1021 * Write the uberblock to all labels of all leaves of the specified vdev.
1022 */
1023 static void
1024 vdev_uberblock_sync(zio_t *zio, uberblock_t *ub, vdev_t *vd, int flags)
1025 {
1026 for (int c = 0; c < vd->vdev_children; c++)
1027 vdev_uberblock_sync(zio, ub, vd->vdev_child[c], flags);
1028
1029 if (!vd->vdev_ops->vdev_op_leaf)
1030 return;
1031
1032 if (!vdev_writeable(vd))
1033 return;
1034
1035 int n = ub->ub_txg & (VDEV_UBERBLOCK_COUNT(vd) - 1);
1036
1037 /* Copy the uberblock_t into the ABD */
1038 abd_t *ub_abd = abd_alloc_for_io(VDEV_UBERBLOCK_SIZE(vd), B_TRUE);
1039 abd_zero(ub_abd, VDEV_UBERBLOCK_SIZE(vd));
1040 abd_copy_from_buf(ub_abd, ub, sizeof (uberblock_t));
1041
1042 for (int l = 0; l < VDEV_LABELS; l++)
1043 vdev_label_write(zio, vd, l, ub_abd,
1044 VDEV_UBERBLOCK_OFFSET(vd, n), VDEV_UBERBLOCK_SIZE(vd),
1045 vdev_uberblock_sync_done, zio->io_private,
1046 flags | ZIO_FLAG_DONT_PROPAGATE);
1047
1048 abd_free(ub_abd);
1049 }
1050
1051 /* Sync the uberblocks to all vdevs in svd[] */
1052 int
1053 vdev_uberblock_sync_list(vdev_t **svd, int svdcount, uberblock_t *ub, int flags)
1054 {
1055 spa_t *spa = svd[0]->vdev_spa;
1056 zio_t *zio;
1057 uint64_t good_writes = 0;
1058
1059 zio = zio_root(spa, NULL, &good_writes, flags);
1060
1061 for (int v = 0; v < svdcount; v++)
1062 vdev_uberblock_sync(zio, ub, svd[v], flags);
1063
1064 (void) zio_wait(zio);
1065
1066 /*
1067 * Flush the uberblocks to disk. This ensures that the odd labels
1068 * are no longer needed (because the new uberblocks and the even
1069 * labels are safely on disk), so it is safe to overwrite them.
1070 */
1071 zio = zio_root(spa, NULL, NULL, flags);
1072
1073 for (int v = 0; v < svdcount; v++)
1074 zio_flush(zio, svd[v]);
1075
1076 (void) zio_wait(zio);
1077
1078 return (good_writes >= 1 ? 0 : EIO);
1079 }
1080
1081 /*
1082 * On success, increment the count of good writes for our top-level vdev.
1083 */
1084 static void
1085 vdev_label_sync_done(zio_t *zio)
1086 {
1087 uint64_t *good_writes = zio->io_private;
1088
1089 if (zio->io_error == 0)
1090 atomic_inc_64(good_writes);
1091 }
1092
1093 /*
1094 * If there weren't enough good writes, indicate failure to the parent.
1095 */
1096 static void
1097 vdev_label_sync_top_done(zio_t *zio)
1098 {
1099 uint64_t *good_writes = zio->io_private;
1100
1101 if (*good_writes == 0)
1102 zio->io_error = SET_ERROR(EIO);
1103
1104 kmem_free(good_writes, sizeof (uint64_t));
1105 }
1106
1107 /*
1108 * We ignore errors for log and cache devices, simply free the private data.
1109 */
1110 static void
1111 vdev_label_sync_ignore_done(zio_t *zio)
1112 {
1113 kmem_free(zio->io_private, sizeof (uint64_t));
1114 }
1115
1116 /*
1117 * Write all even or odd labels to all leaves of the specified vdev.
1118 */
1119 static void
1120 vdev_label_sync(zio_t *zio, vdev_t *vd, int l, uint64_t txg, int flags)
1121 {
1122 nvlist_t *label;
1123 vdev_phys_t *vp;
1124 abd_t *vp_abd;
1125 char *buf;
1126 size_t buflen;
1127
1128 for (int c = 0; c < vd->vdev_children; c++)
1129 vdev_label_sync(zio, vd->vdev_child[c], l, txg, flags);
1130
1131 if (!vd->vdev_ops->vdev_op_leaf)
1132 return;
1133
1134 if (!vdev_writeable(vd))
1135 return;
1136
1137 /*
1138 * Generate a label describing the top-level config to which we belong.
1139 */
1140 label = spa_config_generate(vd->vdev_spa, vd, txg, B_FALSE);
1141
1142 vp_abd = abd_alloc_linear(sizeof (vdev_phys_t), B_TRUE);
1143 abd_zero(vp_abd, sizeof (vdev_phys_t));
1144 vp = abd_to_buf(vp_abd);
1145
1146 buf = vp->vp_nvlist;
1147 buflen = sizeof (vp->vp_nvlist);
1148
1149 if (nvlist_pack(label, &buf, &buflen, NV_ENCODE_XDR, KM_SLEEP) == 0) {
1150 for (; l < VDEV_LABELS; l += 2) {
1151 vdev_label_write(zio, vd, l, vp_abd,
1152 offsetof(vdev_label_t, vl_vdev_phys),
1153 sizeof (vdev_phys_t),
1154 vdev_label_sync_done, zio->io_private,
1155 flags | ZIO_FLAG_DONT_PROPAGATE);
1156 }
1157 }
1158
1159 abd_free(vp_abd);
1160 nvlist_free(label);
1161 }
1162
1163 int
1164 vdev_label_sync_list(spa_t *spa, int l, uint64_t txg, int flags)
1165 {
1166 list_t *dl = &spa->spa_config_dirty_list;
1167 vdev_t *vd;
1168 zio_t *zio;
1169 int error;
1170
1171 /*
1172 * Write the new labels to disk.
1173 */
1174 zio = zio_root(spa, NULL, NULL, flags);
1175
1176 for (vd = list_head(dl); vd != NULL; vd = list_next(dl, vd)) {
1177 uint64_t *good_writes = kmem_zalloc(sizeof (uint64_t),
1178 KM_SLEEP);
1179
1180 ASSERT(!vd->vdev_ishole);
1181
1182 zio_t *vio = zio_null(zio, spa, NULL,
1183 (vd->vdev_islog || vd->vdev_aux != NULL) ?
1184 vdev_label_sync_ignore_done : vdev_label_sync_top_done,
1185 good_writes, flags);
1186 vdev_label_sync(vio, vd, l, txg, flags);
1187 zio_nowait(vio);
1188 }
1189
1190 error = zio_wait(zio);
1191
1192 /*
1193 * Flush the new labels to disk.
1194 */
1195 zio = zio_root(spa, NULL, NULL, flags);
1196
1197 for (vd = list_head(dl); vd != NULL; vd = list_next(dl, vd))
1198 zio_flush(zio, vd);
1199
1200 (void) zio_wait(zio);
1201
1202 return (error);
1203 }
1204
1205 /*
1206 * Sync the uberblock and any changes to the vdev configuration.
1207 *
1208 * The order of operations is carefully crafted to ensure that
1209 * if the system panics or loses power at any time, the state on disk
1210 * is still transactionally consistent. The in-line comments below
1211 * describe the failure semantics at each stage.
1212 *
1213 * Moreover, vdev_config_sync() is designed to be idempotent: if it fails
1214 * at any time, you can just call it again, and it will resume its work.
1215 */
1216 int
1217 vdev_config_sync(vdev_t **svd, int svdcount, uint64_t txg)
1218 {
1219 spa_t *spa = svd[0]->vdev_spa;
1220 uberblock_t *ub = &spa->spa_uberblock;
1221 vdev_t *vd;
1222 zio_t *zio;
1223 int error = 0;
1224 int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL;
1225
1226 retry:
1227 /*
1228 * Normally, we don't want to try too hard to write every label and
1229 * uberblock. If there is a flaky disk, we don't want the rest of the
1230 * sync process to block while we retry. But if we can't write a
1231 * single label out, we should retry with ZIO_FLAG_TRYHARD before
1232 * bailing out and declaring the pool faulted.
1233 */
1234 if (error != 0) {
1235 if ((flags & ZIO_FLAG_TRYHARD) != 0)
1236 return (error);
1237 flags |= ZIO_FLAG_TRYHARD;
1238 }
1239
1240 ASSERT(ub->ub_txg <= txg);
1241
1242 /*
1243 * If this isn't a resync due to I/O errors,
1244 * and nothing changed in this transaction group,
1245 * and the vdev configuration hasn't changed,
1246 * then there's nothing to do.
1247 */
1248 if (ub->ub_txg < txg &&
1249 uberblock_update(ub, spa->spa_root_vdev, txg) == B_FALSE &&
1250 list_is_empty(&spa->spa_config_dirty_list))
1251 return (0);
1252
1253 if (txg > spa_freeze_txg(spa))
1254 return (0);
1255
1256 ASSERT(txg <= spa->spa_final_txg);
1257
1258 /*
1259 * Flush the write cache of every disk that's been written to
1260 * in this transaction group. This ensures that all blocks
1261 * written in this txg will be committed to stable storage
1262 * before any uberblock that references them.
1263 */
1264 zio = zio_root(spa, NULL, NULL, flags);
1265
1266 for (vd = txg_list_head(&spa->spa_vdev_txg_list, TXG_CLEAN(txg)); vd;
1267 vd = txg_list_next(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg)))
1268 zio_flush(zio, vd);
1269
1270 (void) zio_wait(zio);
1271
1272 /*
1273 * Sync out the even labels (L0, L2) for every dirty vdev. If the
1274 * system dies in the middle of this process, that's OK: all of the
1275 * even labels that made it to disk will be newer than any uberblock,
1276 * and will therefore be considered invalid. The odd labels (L1, L3),
1277 * which have not yet been touched, will still be valid. We flush
1278 * the new labels to disk to ensure that all even-label updates
1279 * are committed to stable storage before the uberblock update.
1280 */
1281 if ((error = vdev_label_sync_list(spa, 0, txg, flags)) != 0)
1282 goto retry;
1283
1284 /*
1285 * Sync the uberblocks to all vdevs in svd[].
1286 * If the system dies in the middle of this step, there are two cases
1287 * to consider, and the on-disk state is consistent either way:
1288 *
1289 * (1) If none of the new uberblocks made it to disk, then the
1290 * previous uberblock will be the newest, and the odd labels
1291 * (which had not yet been touched) will be valid with respect
1292 * to that uberblock.
1293 *
1294 * (2) If one or more new uberblocks made it to disk, then they
1295 * will be the newest, and the even labels (which had all
1296 * been successfully committed) will be valid with respect
1297 * to the new uberblocks.
1298 */
1299 if ((error = vdev_uberblock_sync_list(svd, svdcount, ub, flags)) != 0)
1300 goto retry;
1301
1302 /*
1303 * Sync out odd labels for every dirty vdev. If the system dies
1304 * in the middle of this process, the even labels and the new
1305 * uberblocks will suffice to open the pool. The next time
1306 * the pool is opened, the first thing we'll do -- before any
1307 * user data is modified -- is mark every vdev dirty so that
1308 * all labels will be brought up to date. We flush the new labels
1309 * to disk to ensure that all odd-label updates are committed to
1310 * stable storage before the next transaction group begins.
1311 */
1312 if ((error = vdev_label_sync_list(spa, 1, txg, flags)) != 0)
1313 goto retry;
1314
1315 return (0);
1316 }