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) 2013 by Delphix. All rights reserved.
25 */
26
27 /*
28 * Virtual Device Labels
29 * ---------------------
30 *
31 * The vdev label serves several distinct purposes:
32 *
33 * 1. Uniquely identify this device as part of a ZFS pool and confirm its
34 * identity within the pool.
35 *
36 * 2. Verify that all the devices given in a configuration are present
37 * within the pool.
38 *
39 * 3. Determine the uberblock for the pool.
40 *
41 * 4. In case of an import operation, determine the configuration of the
42 * toplevel vdev of which it is a part.
43 *
44 * 5. If an import operation cannot find all the devices in the pool,
45 * provide enough information to the administrator to determine which
46 * devices are missing.
47 *
48 * It is important to note that while the kernel is responsible for writing the
49 * label, it only consumes the information in the first three cases. The
50 * latter information is only consumed in userland when determining the
51 * configuration to import a pool.
52 *
53 *
54 * Label Organization
55 * ------------------
56 *
57 * Before describing the contents of the label, it's important to understand how
58 * the labels are written and updated with respect to the uberblock.
59 *
60 * When the pool configuration is altered, either because it was newly created
61 * or a device was added, we want to update all the labels such that we can deal
62 * with fatal failure at any point. To this end, each disk has two labels which
63 * are updated before and after the uberblock is synced. Assuming we have
64 * labels and an uberblock with the following transaction groups:
65 *
66 * L1 UB L2
67 * +------+ +------+ +------+
68 * | | | | | |
69 * | t10 | | t10 | | t10 |
70 * | | | | | |
71 * +------+ +------+ +------+
72 *
73 * In this stable state, the labels and the uberblock were all updated within
74 * the same transaction group (10). Each label is mirrored and checksummed, so
75 * that we can detect when we fail partway through writing the label.
76 *
77 * In order to identify which labels are valid, the labels are written in the
78 * following manner:
79 *
80 * 1. For each vdev, update 'L1' to the new label
81 * 2. Update the uberblock
82 * 3. For each vdev, update 'L2' to the new label
83 *
84 * Given arbitrary failure, we can determine the correct label to use based on
85 * the transaction group. If we fail after updating L1 but before updating the
86 * UB, we will notice that L1's transaction group is greater than the uberblock,
87 * so L2 must be valid. If we fail after writing the uberblock but before
88 * writing L2, we will notice that L2's transaction group is less than L1, and
89 * therefore L1 is valid.
90 *
91 * Another added complexity is that not every label is updated when the config
92 * is synced. If we add a single device, we do not want to have to re-write
93 * every label for every device in the pool. This means that both L1 and L2 may
94 * be older than the pool uberblock, because the necessary information is stored
95 * on another vdev.
96 *
97 *
98 * On-disk Format
99 * --------------
100 *
101 * The vdev label consists of two distinct parts, and is wrapped within the
102 * vdev_label_t structure. The label includes 8k of padding to permit legacy
103 * VTOC disk labels, but is otherwise ignored.
104 *
105 * The first half of the label is a packed nvlist which contains pool wide
106 * properties, per-vdev properties, and configuration information. It is
107 * described in more detail below.
108 *
109 * The latter half of the label consists of a redundant array of uberblocks.
110 * These uberblocks are updated whenever a transaction group is committed,
111 * or when the configuration is updated. When a pool is loaded, we scan each
112 * vdev for the 'best' uberblock.
113 *
114 *
115 * Configuration Information
116 * -------------------------
117 *
118 * The nvlist describing the pool and vdev contains the following elements:
119 *
120 * version ZFS on-disk version
121 * name Pool name
122 * state Pool state
123 * txg Transaction group in which this label was written
124 * pool_guid Unique identifier for this pool
125 * vdev_tree An nvlist describing vdev tree.
126 * features_for_read
127 * An nvlist of the features necessary for reading the MOS.
128 *
129 * Each leaf device label also contains the following:
130 *
131 * top_guid Unique ID for top-level vdev in which this is contained
132 * guid Unique ID for the leaf vdev
133 *
134 * The 'vs' configuration follows the format described in 'spa_config.c'.
135 */
136
137 #include <sys/zfs_context.h>
138 #include <sys/spa.h>
139 #include <sys/spa_impl.h>
140 #include <sys/dmu.h>
141 #include <sys/zap.h>
142 #include <sys/vdev.h>
143 #include <sys/vdev_impl.h>
144 #include <sys/uberblock_impl.h>
145 #include <sys/metaslab.h>
146 #include <sys/zio.h>
147 #include <sys/dsl_scan.h>
148 #include <sys/fs/zfs.h>
149
150 /*
151 * Basic routines to read and write from a vdev label.
152 * Used throughout the rest of this file.
153 */
154 uint64_t
155 vdev_label_offset(uint64_t psize, int l, uint64_t offset)
156 {
157 ASSERT(offset < sizeof (vdev_label_t));
158 ASSERT(P2PHASE_TYPED(psize, sizeof (vdev_label_t), uint64_t) == 0);
159
160 return (offset + l * sizeof (vdev_label_t) + (l < VDEV_LABELS / 2 ?
161 0 : psize - VDEV_LABELS * sizeof (vdev_label_t)));
162 }
163
164 /*
165 * Returns back the vdev label associated with the passed in offset.
166 */
167 int
168 vdev_label_number(uint64_t psize, uint64_t offset)
169 {
170 int l;
171
172 if (offset >= psize - VDEV_LABEL_END_SIZE) {
173 offset -= psize - VDEV_LABEL_END_SIZE;
174 offset += (VDEV_LABELS / 2) * sizeof (vdev_label_t);
175 }
176 l = offset / sizeof (vdev_label_t);
177 return (l < VDEV_LABELS ? l : -1);
178 }
179
180 static void
181 vdev_label_read(zio_t *zio, vdev_t *vd, int l, void *buf, uint64_t offset,
182 uint64_t size, zio_done_func_t *done, void *private, int flags)
183 {
184 ASSERT(spa_config_held(zio->io_spa, SCL_STATE_ALL, RW_WRITER) ==
185 SCL_STATE_ALL);
186 ASSERT(flags & ZIO_FLAG_CONFIG_WRITER);
187
188 zio_nowait(zio_read_phys(zio, vd,
189 vdev_label_offset(vd->vdev_psize, l, offset),
190 size, buf, ZIO_CHECKSUM_LABEL, done, private,
191 ZIO_PRIORITY_SYNC_READ, flags, B_TRUE));
192 }
193
194 static void
195 vdev_label_write(zio_t *zio, vdev_t *vd, int l, void *buf, uint64_t offset,
196 uint64_t size, zio_done_func_t *done, void *private, int flags)
197 {
198 ASSERT(spa_config_held(zio->io_spa, SCL_ALL, RW_WRITER) == SCL_ALL ||
199 (spa_config_held(zio->io_spa, SCL_CONFIG | SCL_STATE, RW_READER) ==
200 (SCL_CONFIG | SCL_STATE) &&
201 dsl_pool_sync_context(spa_get_dsl(zio->io_spa))));
202 ASSERT(flags & ZIO_FLAG_CONFIG_WRITER);
203
204 zio_nowait(zio_write_phys(zio, vd,
205 vdev_label_offset(vd->vdev_psize, l, offset),
206 size, buf, ZIO_CHECKSUM_LABEL, done, private,
207 ZIO_PRIORITY_SYNC_WRITE, flags, B_TRUE));
208 }
209
210 /*
211 * Generate the nvlist representing this vdev's config.
212 */
213 nvlist_t *
214 vdev_config_generate(spa_t *spa, vdev_t *vd, boolean_t getstats,
215 vdev_config_flag_t flags)
216 {
217 nvlist_t *nv = NULL;
218
219 VERIFY(nvlist_alloc(&nv, NV_UNIQUE_NAME, KM_SLEEP) == 0);
220
221 VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_TYPE,
222 vd->vdev_ops->vdev_op_type) == 0);
223 if (!(flags & (VDEV_CONFIG_SPARE | VDEV_CONFIG_L2CACHE)))
224 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ID, vd->vdev_id)
225 == 0);
226 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_GUID, vd->vdev_guid) == 0);
227
228 if (vd->vdev_path != NULL)
229 VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_PATH,
230 vd->vdev_path) == 0);
231
232 if (vd->vdev_devid != NULL)
233 VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_DEVID,
234 vd->vdev_devid) == 0);
235
236 if (vd->vdev_physpath != NULL)
237 VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_PHYS_PATH,
238 vd->vdev_physpath) == 0);
239
240 if (vd->vdev_fru != NULL)
241 VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_FRU,
242 vd->vdev_fru) == 0);
243
244 if (vd->vdev_nparity != 0) {
245 ASSERT(strcmp(vd->vdev_ops->vdev_op_type,
246 VDEV_TYPE_RAIDZ) == 0);
247
248 /*
249 * Make sure someone hasn't managed to sneak a fancy new vdev
250 * into a crufty old storage pool.
251 */
252 ASSERT(vd->vdev_nparity == 1 ||
253 (vd->vdev_nparity <= 2 &&
254 spa_version(spa) >= SPA_VERSION_RAIDZ2) ||
255 (vd->vdev_nparity <= 3 &&
256 spa_version(spa) >= SPA_VERSION_RAIDZ3));
257
258 /*
259 * Note that we'll add the nparity tag even on storage pools
260 * that only support a single parity device -- older software
261 * will just ignore it.
262 */
263 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_NPARITY,
264 vd->vdev_nparity) == 0);
265 }
266
267 if (vd->vdev_wholedisk != -1ULL)
268 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_WHOLE_DISK,
269 vd->vdev_wholedisk) == 0);
270
271 if (vd->vdev_not_present)
272 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_NOT_PRESENT, 1) == 0);
273
274 if (vd->vdev_isspare)
275 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_IS_SPARE, 1) == 0);
276
277 if (!(flags & (VDEV_CONFIG_SPARE | VDEV_CONFIG_L2CACHE)) &&
278 vd == vd->vdev_top) {
279 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_METASLAB_ARRAY,
280 vd->vdev_ms_array) == 0);
281 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_METASLAB_SHIFT,
282 vd->vdev_ms_shift) == 0);
283 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ASHIFT,
284 vd->vdev_ashift) == 0);
285 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ASIZE,
286 vd->vdev_asize) == 0);
287 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_IS_LOG,
288 vd->vdev_islog) == 0);
289 if (vd->vdev_removing)
290 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_REMOVING,
291 vd->vdev_removing) == 0);
292 }
293
294 if (flags & VDEV_CONFIG_L2CACHE)
295 /* indicate that we support L2ARC persistency */
296 VERIFY(nvlist_add_boolean_value(nv,
297 ZPOOL_CONFIG_L2CACHE_PERSISTENT, B_TRUE) == 0);
298
299 if (vd->vdev_dtl_smo.smo_object != 0)
300 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_DTL,
301 vd->vdev_dtl_smo.smo_object) == 0);
302
303 if (vd->vdev_crtxg)
304 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_CREATE_TXG,
305 vd->vdev_crtxg) == 0);
306
307 if (getstats) {
308 vdev_stat_t vs;
309 pool_scan_stat_t ps;
310
311 vdev_get_stats(vd, &vs);
312 VERIFY(nvlist_add_uint64_array(nv, ZPOOL_CONFIG_VDEV_STATS,
313 (uint64_t *)&vs, sizeof (vs) / sizeof (uint64_t)) == 0);
314
315 /* provide either current or previous scan information */
316 if (spa_scan_get_stats(spa, &ps) == 0) {
317 VERIFY(nvlist_add_uint64_array(nv,
318 ZPOOL_CONFIG_SCAN_STATS, (uint64_t *)&ps,
319 sizeof (pool_scan_stat_t) / sizeof (uint64_t))
320 == 0);
321 }
322 }
323
324 if (!vd->vdev_ops->vdev_op_leaf) {
325 nvlist_t **child;
326 int c, idx;
327
328 ASSERT(!vd->vdev_ishole);
329
330 child = kmem_alloc(vd->vdev_children * sizeof (nvlist_t *),
331 KM_SLEEP);
332
333 for (c = 0, idx = 0; c < vd->vdev_children; c++) {
334 vdev_t *cvd = vd->vdev_child[c];
335
336 /*
337 * If we're generating an nvlist of removing
338 * vdevs then skip over any device which is
339 * not being removed.
340 */
341 if ((flags & VDEV_CONFIG_REMOVING) &&
342 !cvd->vdev_removing)
343 continue;
344
345 child[idx++] = vdev_config_generate(spa, cvd,
346 getstats, flags);
347 }
348
349 if (idx) {
350 VERIFY(nvlist_add_nvlist_array(nv,
351 ZPOOL_CONFIG_CHILDREN, child, idx) == 0);
352 }
353
354 for (c = 0; c < idx; c++)
355 nvlist_free(child[c]);
356
357 kmem_free(child, vd->vdev_children * sizeof (nvlist_t *));
358
359 } else {
360 const char *aux = NULL;
361
362 if (vd->vdev_offline && !vd->vdev_tmpoffline)
363 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_OFFLINE,
364 B_TRUE) == 0);
365 if (vd->vdev_resilvering)
366 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_RESILVERING,
367 B_TRUE) == 0);
368 if (vd->vdev_faulted)
369 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_FAULTED,
370 B_TRUE) == 0);
371 if (vd->vdev_degraded)
372 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_DEGRADED,
373 B_TRUE) == 0);
374 if (vd->vdev_removed)
375 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_REMOVED,
376 B_TRUE) == 0);
377 if (vd->vdev_unspare)
378 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_UNSPARE,
379 B_TRUE) == 0);
380 if (vd->vdev_ishole)
381 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_IS_HOLE,
382 B_TRUE) == 0);
383
384 switch (vd->vdev_stat.vs_aux) {
385 case VDEV_AUX_ERR_EXCEEDED:
386 aux = "err_exceeded";
387 break;
388
389 case VDEV_AUX_EXTERNAL:
390 aux = "external";
391 break;
392 }
393
394 if (aux != NULL)
395 VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_AUX_STATE,
396 aux) == 0);
397
398 if (vd->vdev_splitting && vd->vdev_orig_guid != 0LL) {
399 VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ORIG_GUID,
400 vd->vdev_orig_guid) == 0);
401 }
402 }
403
404 return (nv);
405 }
406
407 /*
408 * Generate a view of the top-level vdevs. If we currently have holes
409 * in the namespace, then generate an array which contains a list of holey
410 * vdevs. Additionally, add the number of top-level children that currently
411 * exist.
412 */
413 void
414 vdev_top_config_generate(spa_t *spa, nvlist_t *config)
415 {
416 vdev_t *rvd = spa->spa_root_vdev;
417 uint64_t *array;
418 uint_t c, idx;
419
420 array = kmem_alloc(rvd->vdev_children * sizeof (uint64_t), KM_SLEEP);
421
422 for (c = 0, idx = 0; c < rvd->vdev_children; c++) {
423 vdev_t *tvd = rvd->vdev_child[c];
424
425 if (tvd->vdev_ishole)
426 array[idx++] = c;
427 }
428
429 if (idx) {
430 VERIFY(nvlist_add_uint64_array(config, ZPOOL_CONFIG_HOLE_ARRAY,
431 array, idx) == 0);
432 }
433
434 VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_VDEV_CHILDREN,
435 rvd->vdev_children) == 0);
436
437 kmem_free(array, rvd->vdev_children * sizeof (uint64_t));
438 }
439
440 /*
441 * Returns the configuration from the label of the given vdev. For vdevs
442 * which don't have a txg value stored on their label (i.e. spares/cache)
443 * or have not been completely initialized (txg = 0) just return
444 * the configuration from the first valid label we find. Otherwise,
445 * find the most up-to-date label that does not exceed the specified
446 * 'txg' value.
447 */
448 nvlist_t *
449 vdev_label_read_config(vdev_t *vd, uint64_t txg)
450 {
451 spa_t *spa = vd->vdev_spa;
452 nvlist_t *config = NULL;
453 vdev_phys_t *vp;
454 zio_t *zio;
455 uint64_t best_txg = 0;
456 int error = 0;
457 int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL |
458 ZIO_FLAG_SPECULATIVE;
459
460 ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
461
462 if (!vdev_readable(vd))
463 return (NULL);
464
465 vp = zio_buf_alloc(sizeof (vdev_phys_t));
466
467 retry:
468 for (int l = 0; l < VDEV_LABELS; l++) {
469 nvlist_t *label = NULL;
470
471 zio = zio_root(spa, NULL, NULL, flags);
472
473 vdev_label_read(zio, vd, l, vp,
474 offsetof(vdev_label_t, vl_vdev_phys),
475 sizeof (vdev_phys_t), NULL, NULL, flags);
476
477 if (zio_wait(zio) == 0 &&
478 nvlist_unpack(vp->vp_nvlist, sizeof (vp->vp_nvlist),
479 &label, 0) == 0) {
480 uint64_t label_txg = 0;
481
482 /*
483 * Auxiliary vdevs won't have txg values in their
484 * labels and newly added vdevs may not have been
485 * completely initialized so just return the
486 * configuration from the first valid label we
487 * encounter.
488 */
489 error = nvlist_lookup_uint64(label,
490 ZPOOL_CONFIG_POOL_TXG, &label_txg);
491 if ((error || label_txg == 0) && !config) {
492 config = label;
493 break;
494 } else if (label_txg <= txg && label_txg > best_txg) {
495 best_txg = label_txg;
496 nvlist_free(config);
497 config = fnvlist_dup(label);
498 }
499 }
500
501 if (label != NULL) {
502 nvlist_free(label);
503 label = NULL;
504 }
505 }
506
507 if (config == NULL && !(flags & ZIO_FLAG_TRYHARD)) {
508 flags |= ZIO_FLAG_TRYHARD;
509 goto retry;
510 }
511
512 zio_buf_free(vp, sizeof (vdev_phys_t));
513
514 return (config);
515 }
516
517 /*
518 * Determine if a device is in use. The 'spare_guid' parameter will be filled
519 * in with the device guid if this spare is active elsewhere on the system.
520 */
521 static boolean_t
522 vdev_inuse(vdev_t *vd, uint64_t crtxg, vdev_labeltype_t reason,
523 uint64_t *spare_guid, uint64_t *l2cache_guid)
524 {
525 spa_t *spa = vd->vdev_spa;
526 uint64_t state, pool_guid, device_guid, txg, spare_pool;
527 uint64_t vdtxg = 0;
528 nvlist_t *label;
529
530 if (spare_guid)
531 *spare_guid = 0ULL;
532 if (l2cache_guid)
533 *l2cache_guid = 0ULL;
534
535 /*
536 * Read the label, if any, and perform some basic sanity checks.
537 */
538 if ((label = vdev_label_read_config(vd, -1ULL)) == NULL)
539 return (B_FALSE);
540
541 (void) nvlist_lookup_uint64(label, ZPOOL_CONFIG_CREATE_TXG,
542 &vdtxg);
543
544 if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE,
545 &state) != 0 ||
546 nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID,
547 &device_guid) != 0) {
548 nvlist_free(label);
549 return (B_FALSE);
550 }
551
552 if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
553 (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID,
554 &pool_guid) != 0 ||
555 nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_TXG,
556 &txg) != 0)) {
557 nvlist_free(label);
558 return (B_FALSE);
559 }
560
561 nvlist_free(label);
562
563 /*
564 * Check to see if this device indeed belongs to the pool it claims to
565 * be a part of. The only way this is allowed is if the device is a hot
566 * spare (which we check for later on).
567 */
568 if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
569 !spa_guid_exists(pool_guid, device_guid) &&
570 !spa_spare_exists(device_guid, NULL, NULL) &&
571 !spa_l2cache_exists(device_guid, NULL))
572 return (B_FALSE);
573
574 /*
575 * If the transaction group is zero, then this an initialized (but
576 * unused) label. This is only an error if the create transaction
577 * on-disk is the same as the one we're using now, in which case the
578 * user has attempted to add the same vdev multiple times in the same
579 * transaction.
580 */
581 if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
582 txg == 0 && vdtxg == crtxg)
583 return (B_TRUE);
584
585 /*
586 * Check to see if this is a spare device. We do an explicit check for
587 * spa_has_spare() here because it may be on our pending list of spares
588 * to add. We also check if it is an l2cache device.
589 */
590 if (spa_spare_exists(device_guid, &spare_pool, NULL) ||
591 spa_has_spare(spa, device_guid)) {
592 if (spare_guid)
593 *spare_guid = device_guid;
594
595 switch (reason) {
596 case VDEV_LABEL_CREATE:
597 case VDEV_LABEL_L2CACHE:
598 return (B_TRUE);
599
600 case VDEV_LABEL_REPLACE:
601 return (!spa_has_spare(spa, device_guid) ||
602 spare_pool != 0ULL);
603
604 case VDEV_LABEL_SPARE:
605 return (spa_has_spare(spa, device_guid));
606 }
607 }
608
609 /*
610 * Check to see if this is an l2cache device.
611 */
612 if (spa_l2cache_exists(device_guid, NULL))
613 return (B_TRUE);
614
615 /*
616 * We can't rely on a pool's state if it's been imported
617 * read-only. Instead we look to see if the pools is marked
618 * read-only in the namespace and set the state to active.
619 */
620 if ((spa = spa_by_guid(pool_guid, device_guid)) != NULL &&
621 spa_mode(spa) == FREAD)
622 state = POOL_STATE_ACTIVE;
623
624 /*
625 * If the device is marked ACTIVE, then this device is in use by another
626 * pool on the system.
627 */
628 return (state == POOL_STATE_ACTIVE);
629 }
630
631 /*
632 * Initialize a vdev label. We check to make sure each leaf device is not in
633 * use, and writable. We put down an initial label which we will later
634 * overwrite with a complete label. Note that it's important to do this
635 * sequentially, not in parallel, so that we catch cases of multiple use of the
636 * same leaf vdev in the vdev we're creating -- e.g. mirroring a disk with
637 * itself.
638 */
639 int
640 vdev_label_init(vdev_t *vd, uint64_t crtxg, vdev_labeltype_t reason)
641 {
642 spa_t *spa = vd->vdev_spa;
643 nvlist_t *label;
644 vdev_phys_t *vp;
645 char *pad2;
646 uberblock_t *ub;
647 zio_t *zio;
648 char *buf;
649 size_t buflen;
650 int error;
651 uint64_t spare_guid, l2cache_guid;
652 int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL;
653
654 ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
655
656 for (int c = 0; c < vd->vdev_children; c++)
657 if ((error = vdev_label_init(vd->vdev_child[c],
658 crtxg, reason)) != 0)
659 return (error);
660
661 /* Track the creation time for this vdev */
662 vd->vdev_crtxg = crtxg;
663
664 if (!vd->vdev_ops->vdev_op_leaf)
665 return (0);
666
667 /*
668 * Dead vdevs cannot be initialized.
669 */
670 if (vdev_is_dead(vd))
671 return (SET_ERROR(EIO));
672
673 /*
674 * Determine if the vdev is in use.
675 */
676 if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_SPLIT &&
677 vdev_inuse(vd, crtxg, reason, &spare_guid, &l2cache_guid))
678 return (SET_ERROR(EBUSY));
679
680 /*
681 * If this is a request to add or replace a spare or l2cache device
682 * that is in use elsewhere on the system, then we must update the
683 * guid (which was initialized to a random value) to reflect the
684 * actual GUID (which is shared between multiple pools).
685 */
686 if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_L2CACHE &&
687 spare_guid != 0ULL) {
688 uint64_t guid_delta = spare_guid - vd->vdev_guid;
689
690 vd->vdev_guid += guid_delta;
691
692 for (vdev_t *pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
693 pvd->vdev_guid_sum += guid_delta;
694
695 /*
696 * If this is a replacement, then we want to fallthrough to the
697 * rest of the code. If we're adding a spare, then it's already
698 * labeled appropriately and we can just return.
699 */
700 if (reason == VDEV_LABEL_SPARE)
701 return (0);
702 ASSERT(reason == VDEV_LABEL_REPLACE ||
703 reason == VDEV_LABEL_SPLIT);
704 }
705
706 if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_SPARE &&
707 l2cache_guid != 0ULL) {
708 uint64_t guid_delta = l2cache_guid - vd->vdev_guid;
709
710 vd->vdev_guid += guid_delta;
711
712 for (vdev_t *pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
713 pvd->vdev_guid_sum += guid_delta;
714
715 /*
716 * If this is a replacement, then we want to fallthrough to the
717 * rest of the code. If we're adding an l2cache, then it's
718 * already labeled appropriately and we can just return.
719 */
720 if (reason == VDEV_LABEL_L2CACHE)
721 return (0);
722 ASSERT(reason == VDEV_LABEL_REPLACE);
723 }
724
725 /*
726 * Initialize its label.
727 */
728 vp = zio_buf_alloc(sizeof (vdev_phys_t));
729 bzero(vp, sizeof (vdev_phys_t));
730
731 /*
732 * Generate a label describing the pool and our top-level vdev.
733 * We mark it as being from txg 0 to indicate that it's not
734 * really part of an active pool just yet. The labels will
735 * be written again with a meaningful txg by spa_sync().
736 */
737 if (reason == VDEV_LABEL_SPARE ||
738 (reason == VDEV_LABEL_REMOVE && vd->vdev_isspare)) {
739 /*
740 * For inactive hot spares, we generate a special label that
741 * identifies as a mutually shared hot spare. We write the
742 * label if we are adding a hot spare, or if we are removing an
743 * active hot spare (in which case we want to revert the
744 * labels).
745 */
746 VERIFY(nvlist_alloc(&label, NV_UNIQUE_NAME, KM_SLEEP) == 0);
747
748 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_VERSION,
749 spa_version(spa)) == 0);
750 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_POOL_STATE,
751 POOL_STATE_SPARE) == 0);
752 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_GUID,
753 vd->vdev_guid) == 0);
754 } else if (reason == VDEV_LABEL_L2CACHE ||
755 (reason == VDEV_LABEL_REMOVE && vd->vdev_isl2cache)) {
756 /*
757 * For level 2 ARC devices, add a special label.
758 */
759 VERIFY(nvlist_alloc(&label, NV_UNIQUE_NAME, KM_SLEEP) == 0);
760
761 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_VERSION,
762 spa_version(spa)) == 0);
763 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_POOL_STATE,
764 POOL_STATE_L2CACHE) == 0);
765 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_GUID,
766 vd->vdev_guid) == 0);
767 } else {
768 uint64_t txg = 0ULL;
769
770 if (reason == VDEV_LABEL_SPLIT)
771 txg = spa->spa_uberblock.ub_txg;
772 label = spa_config_generate(spa, vd, txg, B_FALSE);
773
774 /*
775 * Add our creation time. This allows us to detect multiple
776 * vdev uses as described above, and automatically expires if we
777 * fail.
778 */
779 VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_CREATE_TXG,
780 crtxg) == 0);
781 }
782
783 buf = vp->vp_nvlist;
784 buflen = sizeof (vp->vp_nvlist);
785
786 error = nvlist_pack(label, &buf, &buflen, NV_ENCODE_XDR, KM_SLEEP);
787 if (error != 0) {
788 nvlist_free(label);
789 zio_buf_free(vp, sizeof (vdev_phys_t));
790 /* EFAULT means nvlist_pack ran out of room */
791 return (error == EFAULT ? ENAMETOOLONG : EINVAL);
792 }
793
794 /*
795 * Initialize uberblock template.
796 */
797 ub = zio_buf_alloc(VDEV_UBERBLOCK_RING);
798 bzero(ub, VDEV_UBERBLOCK_RING);
799 *ub = spa->spa_uberblock;
800 ub->ub_txg = 0;
801
802 /* Initialize the 2nd padding area. */
803 pad2 = zio_buf_alloc(VDEV_PAD_SIZE);
804 bzero(pad2, VDEV_PAD_SIZE);
805
806 /*
807 * Write everything in parallel.
808 */
809 retry:
810 zio = zio_root(spa, NULL, NULL, flags);
811
812 for (int l = 0; l < VDEV_LABELS; l++) {
813
814 vdev_label_write(zio, vd, l, vp,
815 offsetof(vdev_label_t, vl_vdev_phys),
816 sizeof (vdev_phys_t), NULL, NULL, flags);
817
818 /*
819 * Skip the 1st padding area.
820 * Zero out the 2nd padding area where it might have
821 * left over data from previous filesystem format.
822 */
823 vdev_label_write(zio, vd, l, pad2,
824 offsetof(vdev_label_t, vl_pad2),
825 VDEV_PAD_SIZE, NULL, NULL, flags);
826
827 vdev_label_write(zio, vd, l, ub,
828 offsetof(vdev_label_t, vl_uberblock),
829 VDEV_UBERBLOCK_RING, NULL, NULL, flags);
830 }
831
832 error = zio_wait(zio);
833
834 if (error != 0 && !(flags & ZIO_FLAG_TRYHARD)) {
835 flags |= ZIO_FLAG_TRYHARD;
836 goto retry;
837 }
838
839 nvlist_free(label);
840 zio_buf_free(pad2, VDEV_PAD_SIZE);
841 zio_buf_free(ub, VDEV_UBERBLOCK_RING);
842 zio_buf_free(vp, sizeof (vdev_phys_t));
843
844 /*
845 * If this vdev hasn't been previously identified as a spare, then we
846 * mark it as such only if a) we are labeling it as a spare, or b) it
847 * exists as a spare elsewhere in the system. Do the same for
848 * level 2 ARC devices.
849 */
850 if (error == 0 && !vd->vdev_isspare &&
851 (reason == VDEV_LABEL_SPARE ||
852 spa_spare_exists(vd->vdev_guid, NULL, NULL)))
853 spa_spare_add(vd);
854
855 if (error == 0 && !vd->vdev_isl2cache &&
856 (reason == VDEV_LABEL_L2CACHE ||
857 spa_l2cache_exists(vd->vdev_guid, NULL)))
858 spa_l2cache_add(vd);
859
860 return (error);
861 }
862
863 /*
864 * ==========================================================================
865 * uberblock load/sync
866 * ==========================================================================
867 */
868
869 /*
870 * Consider the following situation: txg is safely synced to disk. We've
871 * written the first uberblock for txg + 1, and then we lose power. When we
872 * come back up, we fail to see the uberblock for txg + 1 because, say,
873 * it was on a mirrored device and the replica to which we wrote txg + 1
874 * is now offline. If we then make some changes and sync txg + 1, and then
875 * the missing replica comes back, then for a few seconds we'll have two
876 * conflicting uberblocks on disk with the same txg. The solution is simple:
877 * among uberblocks with equal txg, choose the one with the latest timestamp.
878 */
879 static int
880 vdev_uberblock_compare(uberblock_t *ub1, uberblock_t *ub2)
881 {
882 if (ub1->ub_txg < ub2->ub_txg)
883 return (-1);
884 if (ub1->ub_txg > ub2->ub_txg)
885 return (1);
886
887 if (ub1->ub_timestamp < ub2->ub_timestamp)
888 return (-1);
889 if (ub1->ub_timestamp > ub2->ub_timestamp)
890 return (1);
891
892 return (0);
893 }
894
895 struct ubl_cbdata {
896 uberblock_t *ubl_ubbest; /* Best uberblock */
897 vdev_t *ubl_vd; /* vdev associated with the above */
898 };
899
900 static void
901 vdev_uberblock_load_done(zio_t *zio)
902 {
903 vdev_t *vd = zio->io_vd;
904 spa_t *spa = zio->io_spa;
905 zio_t *rio = zio->io_private;
906 uberblock_t *ub = zio->io_data;
907 struct ubl_cbdata *cbp = rio->io_private;
908
909 ASSERT3U(zio->io_size, ==, VDEV_UBERBLOCK_SIZE(vd));
910
911 if (zio->io_error == 0 && uberblock_verify(ub) == 0) {
912 mutex_enter(&rio->io_lock);
913 if (ub->ub_txg <= spa->spa_load_max_txg &&
914 vdev_uberblock_compare(ub, cbp->ubl_ubbest) > 0) {
915 /*
916 * Keep track of the vdev in which this uberblock
917 * was found. We will use this information later
918 * to obtain the config nvlist associated with
919 * this uberblock.
920 */
921 *cbp->ubl_ubbest = *ub;
922 cbp->ubl_vd = vd;
923 }
924 mutex_exit(&rio->io_lock);
925 }
926
927 zio_buf_free(zio->io_data, zio->io_size);
928 }
929
930 static void
931 vdev_uberblock_load_impl(zio_t *zio, vdev_t *vd, int flags,
932 struct ubl_cbdata *cbp)
933 {
934 for (int c = 0; c < vd->vdev_children; c++)
935 vdev_uberblock_load_impl(zio, vd->vdev_child[c], flags, cbp);
936
937 if (vd->vdev_ops->vdev_op_leaf && vdev_readable(vd)) {
938 for (int l = 0; l < VDEV_LABELS; l++) {
939 for (int n = 0; n < VDEV_UBERBLOCK_COUNT(vd); n++) {
940 vdev_label_read(zio, vd, l,
941 zio_buf_alloc(VDEV_UBERBLOCK_SIZE(vd)),
942 VDEV_UBERBLOCK_OFFSET(vd, n),
943 VDEV_UBERBLOCK_SIZE(vd),
944 vdev_uberblock_load_done, zio, flags);
945 }
946 }
947 }
948 }
949
950 /*
951 * Reads the 'best' uberblock from disk along with its associated
952 * configuration. First, we read the uberblock array of each label of each
953 * vdev, keeping track of the uberblock with the highest txg in each array.
954 * Then, we read the configuration from the same vdev as the best uberblock.
955 */
956 void
957 vdev_uberblock_load(vdev_t *rvd, uberblock_t *ub, nvlist_t **config)
958 {
959 zio_t *zio;
960 spa_t *spa = rvd->vdev_spa;
961 struct ubl_cbdata cb;
962 int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL |
963 ZIO_FLAG_SPECULATIVE | ZIO_FLAG_TRYHARD;
964
965 ASSERT(ub);
966 ASSERT(config);
967
968 bzero(ub, sizeof (uberblock_t));
969 *config = NULL;
970
971 cb.ubl_ubbest = ub;
972 cb.ubl_vd = NULL;
973
974 spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
975 zio = zio_root(spa, NULL, &cb, flags);
976 vdev_uberblock_load_impl(zio, rvd, flags, &cb);
977 (void) zio_wait(zio);
978
979 /*
980 * It's possible that the best uberblock was discovered on a label
981 * that has a configuration which was written in a future txg.
982 * Search all labels on this vdev to find the configuration that
983 * matches the txg for our uberblock.
984 */
985 if (cb.ubl_vd != NULL)
986 *config = vdev_label_read_config(cb.ubl_vd, ub->ub_txg);
987 spa_config_exit(spa, SCL_ALL, FTAG);
988 }
989
990 /*
991 * On success, increment root zio's count of good writes.
992 * We only get credit for writes to known-visible vdevs; see spa_vdev_add().
993 */
994 static void
995 vdev_uberblock_sync_done(zio_t *zio)
996 {
997 uint64_t *good_writes = zio->io_private;
998
999 if (zio->io_error == 0 && zio->io_vd->vdev_top->vdev_ms_array != 0)
1000 atomic_add_64(good_writes, 1);
1001 }
1002
1003 /*
1004 * Write the uberblock to all labels of all leaves of the specified vdev.
1005 */
1006 static void
1007 vdev_uberblock_sync(zio_t *zio, uberblock_t *ub, vdev_t *vd, int flags)
1008 {
1009 uberblock_t *ubbuf;
1010 int n;
1011
1012 for (int c = 0; c < vd->vdev_children; c++)
1013 vdev_uberblock_sync(zio, ub, vd->vdev_child[c], flags);
1014
1015 if (!vd->vdev_ops->vdev_op_leaf)
1016 return;
1017
1018 if (!vdev_writeable(vd))
1019 return;
1020
1021 n = ub->ub_txg & (VDEV_UBERBLOCK_COUNT(vd) - 1);
1022
1023 ubbuf = zio_buf_alloc(VDEV_UBERBLOCK_SIZE(vd));
1024 bzero(ubbuf, VDEV_UBERBLOCK_SIZE(vd));
1025 *ubbuf = *ub;
1026
1027 for (int l = 0; l < VDEV_LABELS; l++)
1028 vdev_label_write(zio, vd, l, ubbuf,
1029 VDEV_UBERBLOCK_OFFSET(vd, n), VDEV_UBERBLOCK_SIZE(vd),
1030 vdev_uberblock_sync_done, zio->io_private,
1031 flags | ZIO_FLAG_DONT_PROPAGATE);
1032
1033 zio_buf_free(ubbuf, VDEV_UBERBLOCK_SIZE(vd));
1034 }
1035
1036 /* Sync the uberblocks to all vdevs in svd[] */
1037 int
1038 vdev_uberblock_sync_list(vdev_t **svd, int svdcount, uberblock_t *ub, int flags)
1039 {
1040 spa_t *spa = svd[0]->vdev_spa;
1041 zio_t *zio;
1042 uint64_t good_writes = 0;
1043
1044 zio = zio_root(spa, NULL, &good_writes, flags);
1045
1046 for (int v = 0; v < svdcount; v++)
1047 vdev_uberblock_sync(zio, ub, svd[v], flags);
1048
1049 (void) zio_wait(zio);
1050
1051 /*
1052 * Flush the uberblocks to disk. This ensures that the odd labels
1053 * are no longer needed (because the new uberblocks and the even
1054 * labels are safely on disk), so it is safe to overwrite them.
1055 */
1056 zio = zio_root(spa, NULL, NULL, flags);
1057
1058 for (int v = 0; v < svdcount; v++)
1059 zio_flush(zio, svd[v]);
1060
1061 (void) zio_wait(zio);
1062
1063 return (good_writes >= 1 ? 0 : EIO);
1064 }
1065
1066 /*
1067 * On success, increment the count of good writes for our top-level vdev.
1068 */
1069 static void
1070 vdev_label_sync_done(zio_t *zio)
1071 {
1072 uint64_t *good_writes = zio->io_private;
1073
1074 if (zio->io_error == 0)
1075 atomic_add_64(good_writes, 1);
1076 }
1077
1078 /*
1079 * If there weren't enough good writes, indicate failure to the parent.
1080 */
1081 static void
1082 vdev_label_sync_top_done(zio_t *zio)
1083 {
1084 uint64_t *good_writes = zio->io_private;
1085
1086 if (*good_writes == 0)
1087 zio->io_error = SET_ERROR(EIO);
1088
1089 kmem_free(good_writes, sizeof (uint64_t));
1090 }
1091
1092 /*
1093 * We ignore errors for log and cache devices, simply free the private data.
1094 */
1095 static void
1096 vdev_label_sync_ignore_done(zio_t *zio)
1097 {
1098 kmem_free(zio->io_private, sizeof (uint64_t));
1099 }
1100
1101 /*
1102 * Write all even or odd labels to all leaves of the specified vdev.
1103 */
1104 static void
1105 vdev_label_sync(zio_t *zio, vdev_t *vd, int l, uint64_t txg, int flags)
1106 {
1107 nvlist_t *label;
1108 vdev_phys_t *vp;
1109 char *buf;
1110 size_t buflen;
1111
1112 for (int c = 0; c < vd->vdev_children; c++)
1113 vdev_label_sync(zio, vd->vdev_child[c], l, txg, flags);
1114
1115 if (!vd->vdev_ops->vdev_op_leaf)
1116 return;
1117
1118 if (!vdev_writeable(vd))
1119 return;
1120
1121 /*
1122 * Generate a label describing the top-level config to which we belong.
1123 */
1124 label = spa_config_generate(vd->vdev_spa, vd, txg, B_FALSE);
1125
1126 vp = zio_buf_alloc(sizeof (vdev_phys_t));
1127 bzero(vp, sizeof (vdev_phys_t));
1128
1129 buf = vp->vp_nvlist;
1130 buflen = sizeof (vp->vp_nvlist);
1131
1132 if (nvlist_pack(label, &buf, &buflen, NV_ENCODE_XDR, KM_SLEEP) == 0) {
1133 for (; l < VDEV_LABELS; l += 2) {
1134 vdev_label_write(zio, vd, l, vp,
1135 offsetof(vdev_label_t, vl_vdev_phys),
1136 sizeof (vdev_phys_t),
1137 vdev_label_sync_done, zio->io_private,
1138 flags | ZIO_FLAG_DONT_PROPAGATE);
1139 }
1140 }
1141
1142 zio_buf_free(vp, sizeof (vdev_phys_t));
1143 nvlist_free(label);
1144 }
1145
1146 int
1147 vdev_label_sync_list(spa_t *spa, int l, uint64_t txg, int flags)
1148 {
1149 list_t *dl = &spa->spa_config_dirty_list;
1150 vdev_t *vd;
1151 zio_t *zio;
1152 int error;
1153
1154 /*
1155 * Write the new labels to disk.
1156 */
1157 zio = zio_root(spa, NULL, NULL, flags);
1158
1159 for (vd = list_head(dl); vd != NULL; vd = list_next(dl, vd)) {
1160 uint64_t *good_writes = kmem_zalloc(sizeof (uint64_t),
1161 KM_SLEEP);
1162
1163 ASSERT(!vd->vdev_ishole);
1164
1165 zio_t *vio = zio_null(zio, spa, NULL,
1166 (vd->vdev_islog || vd->vdev_aux != NULL) ?
1167 vdev_label_sync_ignore_done : vdev_label_sync_top_done,
1168 good_writes, flags);
1169 vdev_label_sync(vio, vd, l, txg, flags);
1170 zio_nowait(vio);
1171 }
1172
1173 error = zio_wait(zio);
1174
1175 /*
1176 * Flush the new labels to disk.
1177 */
1178 zio = zio_root(spa, NULL, NULL, flags);
1179
1180 for (vd = list_head(dl); vd != NULL; vd = list_next(dl, vd))
1181 zio_flush(zio, vd);
1182
1183 (void) zio_wait(zio);
1184
1185 return (error);
1186 }
1187
1188 /*
1189 * Sync the uberblock and any changes to the vdev configuration.
1190 *
1191 * The order of operations is carefully crafted to ensure that
1192 * if the system panics or loses power at any time, the state on disk
1193 * is still transactionally consistent. The in-line comments below
1194 * describe the failure semantics at each stage.
1195 *
1196 * Moreover, vdev_config_sync() is designed to be idempotent: if it fails
1197 * at any time, you can just call it again, and it will resume its work.
1198 */
1199 int
1200 vdev_config_sync(vdev_t **svd, int svdcount, uint64_t txg, boolean_t tryhard)
1201 {
1202 spa_t *spa = svd[0]->vdev_spa;
1203 uberblock_t *ub = &spa->spa_uberblock;
1204 vdev_t *vd;
1205 zio_t *zio;
1206 int error;
1207 int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL;
1208
1209 /*
1210 * Normally, we don't want to try too hard to write every label and
1211 * uberblock. If there is a flaky disk, we don't want the rest of the
1212 * sync process to block while we retry. But if we can't write a
1213 * single label out, we should retry with ZIO_FLAG_TRYHARD before
1214 * bailing out and declaring the pool faulted.
1215 */
1216 if (tryhard)
1217 flags |= ZIO_FLAG_TRYHARD;
1218
1219 ASSERT(ub->ub_txg <= txg);
1220
1221 /*
1222 * If this isn't a resync due to I/O errors,
1223 * and nothing changed in this transaction group,
1224 * and the vdev configuration hasn't changed,
1225 * then there's nothing to do.
1226 */
1227 if (ub->ub_txg < txg &&
1228 uberblock_update(ub, spa->spa_root_vdev, txg) == B_FALSE &&
1229 list_is_empty(&spa->spa_config_dirty_list))
1230 return (0);
1231
1232 if (txg > spa_freeze_txg(spa))
1233 return (0);
1234
1235 ASSERT(txg <= spa->spa_final_txg);
1236
1237 /*
1238 * Flush the write cache of every disk that's been written to
1239 * in this transaction group. This ensures that all blocks
1240 * written in this txg will be committed to stable storage
1241 * before any uberblock that references them.
1242 */
1243 zio = zio_root(spa, NULL, NULL, flags);
1244
1245 for (vd = txg_list_head(&spa->spa_vdev_txg_list, TXG_CLEAN(txg)); vd;
1246 vd = txg_list_next(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg)))
1247 zio_flush(zio, vd);
1248
1249 (void) zio_wait(zio);
1250
1251 /*
1252 * Sync out the even labels (L0, L2) for every dirty vdev. If the
1253 * system dies in the middle of this process, that's OK: all of the
1254 * even labels that made it to disk will be newer than any uberblock,
1255 * and will therefore be considered invalid. The odd labels (L1, L3),
1256 * which have not yet been touched, will still be valid. We flush
1257 * the new labels to disk to ensure that all even-label updates
1258 * are committed to stable storage before the uberblock update.
1259 */
1260 if ((error = vdev_label_sync_list(spa, 0, txg, flags)) != 0)
1261 return (error);
1262
1263 /*
1264 * Sync the uberblocks to all vdevs in svd[].
1265 * If the system dies in the middle of this step, there are two cases
1266 * to consider, and the on-disk state is consistent either way:
1267 *
1268 * (1) If none of the new uberblocks made it to disk, then the
1269 * previous uberblock will be the newest, and the odd labels
1270 * (which had not yet been touched) will be valid with respect
1271 * to that uberblock.
1272 *
1273 * (2) If one or more new uberblocks made it to disk, then they
1274 * will be the newest, and the even labels (which had all
1275 * been successfully committed) will be valid with respect
1276 * to the new uberblocks.
1277 */
1278 if ((error = vdev_uberblock_sync_list(svd, svdcount, ub, flags)) != 0)
1279 return (error);
1280
1281 /*
1282 * Sync out odd labels for every dirty vdev. If the system dies
1283 * in the middle of this process, the even labels and the new
1284 * uberblocks will suffice to open the pool. The next time
1285 * the pool is opened, the first thing we'll do -- before any
1286 * user data is modified -- is mark every vdev dirty so that
1287 * all labels will be brought up to date. We flush the new labels
1288 * to disk to ensure that all odd-label updates are committed to
1289 * stable storage before the next transaction group begins.
1290 */
1291 return (vdev_label_sync_list(spa, 1, txg, flags));
1292 }