summaryrefslogtreecommitdiffstats
path: root/module/zfs/vdev_rebuild.c
blob: a77ff99faa92425fb0fe6c566a7d61655ab4c943 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 *
 * Copyright (c) 2018, Intel Corporation.
 * Copyright (c) 2020 by Lawrence Livermore National Security, LLC.
 */

#include <sys/vdev_impl.h>
#include <sys/vdev_draid.h>
#include <sys/dsl_scan.h>
#include <sys/spa_impl.h>
#include <sys/metaslab_impl.h>
#include <sys/vdev_rebuild.h>
#include <sys/zio.h>
#include <sys/dmu_tx.h>
#include <sys/arc.h>
#include <sys/zap.h>

/*
 * This file contains the sequential reconstruction implementation for
 * resilvering.  This form of resilvering is internally referred to as device
 * rebuild to avoid conflating it with the traditional healing reconstruction
 * performed by the dsl scan code.
 *
 * When replacing a device, or scrubbing the pool, ZFS has historically used
 * a process called resilvering which is a form of healing reconstruction.
 * This approach has the advantage that as blocks are read from disk their
 * checksums can be immediately verified and the data repaired.  Unfortunately,
 * it also results in a random IO pattern to the disk even when extra care
 * is taken to sequentialize the IO as much as possible.  This substantially
 * increases the time required to resilver the pool and restore redundancy.
 *
 * For mirrored devices it's possible to implement an alternate sequential
 * reconstruction strategy when resilvering.  Sequential reconstruction
 * behaves like a traditional RAID rebuild and reconstructs a device in LBA
 * order without verifying the checksum.  After this phase completes a second
 * scrub phase is started to verify all of the checksums.  This two phase
 * process will take longer than the healing reconstruction described above.
 * However, it has that advantage that after the reconstruction first phase
 * completes redundancy has been restored.  At this point the pool can incur
 * another device failure without risking data loss.
 *
 * There are a few noteworthy limitations and other advantages of resilvering
 * using sequential reconstruction vs healing reconstruction.
 *
 * Limitations:
 *
 *   - Sequential reconstruction is not possible on RAIDZ due to its
 *     variable stripe width.  Note dRAID uses a fixed stripe width which
 *     avoids this issue, but comes at the expense of some usable capacity.
 *
 *   - Block checksums are not verified during sequential reconstruction.
 *     Similar to traditional RAID the parity/mirror data is reconstructed
 *     but cannot be immediately double checked.  For this reason when the
 *     last active resilver completes the pool is automatically scrubbed
 *     by default.
 *
 *   - Deferred resilvers using sequential reconstruction are not currently
 *     supported.  When adding another vdev to an active top-level resilver
 *     it must be restarted.
 *
 * Advantages:
 *
 *   - Sequential reconstruction is performed in LBA order which may be faster
 *     than healing reconstruction particularly when using using HDDs (or
 *     especially with SMR devices).  Only allocated capacity is resilvered.
 *
 *   - Sequential reconstruction is not constrained by ZFS block boundaries.
 *     This allows it to issue larger IOs to disk which span multiple blocks
 *     allowing all of these logical blocks to be repaired with a single IO.
 *
 *   - Unlike a healing resilver or scrub which are pool wide operations,
 *     sequential reconstruction is handled by the top-level vdevs.  This
 *     allows for it to be started or canceled on a top-level vdev without
 *     impacting any other top-level vdevs in the pool.
 *
 *   - Data only referenced by a pool checkpoint will be repaired because
 *     that space is reflected in the space maps.  This differs for a
 *     healing resilver or scrub which will not repair that data.
 */


/*
 * Size of rebuild reads; defaults to 1MiB per data disk and is capped at
 * SPA_MAXBLOCKSIZE.
 */
unsigned long zfs_rebuild_max_segment = 1024 * 1024;

/*
 * Maximum number of parallelly executed bytes per leaf vdev caused by a
 * sequential resilver.  We attempt to strike a balance here between keeping
 * the vdev queues full of I/Os at all times and not overflowing the queues
 * to cause long latency, which would cause long txg sync times.
 *
 * A large default value can be safely used here because the default target
 * segment size is also large (zfs_rebuild_max_segment=1M).  This helps keep
 * the queue depth short.
 *
 * 32MB was selected as the default value to achieve good performance with
 * a large 90-drive dRAID HDD configuration (draid2:8d:90c:2s). A sequential
 * rebuild was unable to saturate all of the drives using smaller values.
 * With a value of 32MB the sequential resilver write rate was measured at
 * 800MB/s sustained while rebuilding to a distributed spare.
 */
unsigned long zfs_rebuild_vdev_limit = 32 << 20;

/*
 * Automatically start a pool scrub when the last active sequential resilver
 * completes in order to verify the checksums of all blocks which have been
 * resilvered. This option is enabled by default and is strongly recommended.
 */
int zfs_rebuild_scrub_enabled = 1;

/*
 * For vdev_rebuild_initiate_sync() and vdev_rebuild_reset_sync().
 */
static void vdev_rebuild_thread(void *arg);

/*
 * Clear the per-vdev rebuild bytes value for a vdev tree.
 */
static void
clear_rebuild_bytes(vdev_t *vd)
{
	vdev_stat_t *vs = &vd->vdev_stat;

	for (uint64_t i = 0; i < vd->vdev_children; i++)
		clear_rebuild_bytes(vd->vdev_child[i]);

	mutex_enter(&vd->vdev_stat_lock);
	vs->vs_rebuild_processed = 0;
	mutex_exit(&vd->vdev_stat_lock);
}

/*
 * Determines whether a vdev_rebuild_thread() should be stopped.
 */
static boolean_t
vdev_rebuild_should_stop(vdev_t *vd)
{
	return (!vdev_writeable(vd) || vd->vdev_removing ||
	    vd->vdev_rebuild_exit_wanted ||
	    vd->vdev_rebuild_cancel_wanted ||
	    vd->vdev_rebuild_reset_wanted);
}

/*
 * Determine if the rebuild should be canceled.  This may happen when all
 * vdevs with MISSING DTLs are detached.
 */
static boolean_t
vdev_rebuild_should_cancel(vdev_t *vd)
{
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;

	if (!vdev_resilver_needed(vd, &vrp->vrp_min_txg, &vrp->vrp_max_txg))
		return (B_TRUE);

	return (B_FALSE);
}

/*
 * The sync task for updating the on-disk state of a rebuild.  This is
 * scheduled by vdev_rebuild_range().
 */
static void
vdev_rebuild_update_sync(void *arg, dmu_tx_t *tx)
{
	int vdev_id = (uintptr_t)arg;
	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
	vdev_t *vd = vdev_lookup_top(spa, vdev_id);
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
	uint64_t txg = dmu_tx_get_txg(tx);

	mutex_enter(&vd->vdev_rebuild_lock);

	if (vr->vr_scan_offset[txg & TXG_MASK] > 0) {
		vrp->vrp_last_offset = vr->vr_scan_offset[txg & TXG_MASK];
		vr->vr_scan_offset[txg & TXG_MASK] = 0;
	}

	vrp->vrp_scan_time_ms = vr->vr_prev_scan_time_ms +
	    NSEC2MSEC(gethrtime() - vr->vr_pass_start_time);

	VERIFY0(zap_update(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap,
	    VDEV_TOP_ZAP_VDEV_REBUILD_PHYS, sizeof (uint64_t),
	    REBUILD_PHYS_ENTRIES, vrp, tx));

	mutex_exit(&vd->vdev_rebuild_lock);
}

/*
 * Initialize the on-disk state for a new rebuild, start the rebuild thread.
 */
static void
vdev_rebuild_initiate_sync(void *arg, dmu_tx_t *tx)
{
	int vdev_id = (uintptr_t)arg;
	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
	vdev_t *vd = vdev_lookup_top(spa, vdev_id);
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;

	ASSERT(vd->vdev_rebuilding);

	spa_feature_incr(vd->vdev_spa, SPA_FEATURE_DEVICE_REBUILD, tx);

	mutex_enter(&vd->vdev_rebuild_lock);
	bzero(vrp, sizeof (uint64_t) * REBUILD_PHYS_ENTRIES);
	vrp->vrp_rebuild_state = VDEV_REBUILD_ACTIVE;
	vrp->vrp_min_txg = 0;
	vrp->vrp_max_txg = dmu_tx_get_txg(tx);
	vrp->vrp_start_time = gethrestime_sec();
	vrp->vrp_scan_time_ms = 0;
	vr->vr_prev_scan_time_ms = 0;

	/*
	 * Rebuilds are currently only used when replacing a device, in which
	 * case there must be DTL_MISSING entries.  In the future, we could
	 * allow rebuilds to be used in a way similar to a scrub.  This would
	 * be useful because it would allow us to rebuild the space used by
	 * pool checkpoints.
	 */
	VERIFY(vdev_resilver_needed(vd, &vrp->vrp_min_txg, &vrp->vrp_max_txg));

	VERIFY0(zap_update(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap,
	    VDEV_TOP_ZAP_VDEV_REBUILD_PHYS, sizeof (uint64_t),
	    REBUILD_PHYS_ENTRIES, vrp, tx));

	spa_history_log_internal(spa, "rebuild", tx,
	    "vdev_id=%llu vdev_guid=%llu started",
	    (u_longlong_t)vd->vdev_id, (u_longlong_t)vd->vdev_guid);

	ASSERT3P(vd->vdev_rebuild_thread, ==, NULL);
	vd->vdev_rebuild_thread = thread_create(NULL, 0,
	    vdev_rebuild_thread, vd, 0, &p0, TS_RUN, maxclsyspri);

	mutex_exit(&vd->vdev_rebuild_lock);
}

static void
vdev_rebuild_log_notify(spa_t *spa, vdev_t *vd, char *name)
{
	nvlist_t *aux = fnvlist_alloc();

	fnvlist_add_string(aux, ZFS_EV_RESILVER_TYPE, "sequential");
	spa_event_notify(spa, vd, aux, name);
	nvlist_free(aux);
}

/*
 * Called to request that a new rebuild be started.  The feature will remain
 * active for the duration of the rebuild, then revert to the enabled state.
 */
static void
vdev_rebuild_initiate(vdev_t *vd)
{
	spa_t *spa = vd->vdev_spa;

	ASSERT(vd->vdev_top == vd);
	ASSERT(MUTEX_HELD(&vd->vdev_rebuild_lock));
	ASSERT(!vd->vdev_rebuilding);

	dmu_tx_t *tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir);
	VERIFY0(dmu_tx_assign(tx, TXG_WAIT));

	vd->vdev_rebuilding = B_TRUE;

	dsl_sync_task_nowait(spa_get_dsl(spa), vdev_rebuild_initiate_sync,
	    (void *)(uintptr_t)vd->vdev_id, tx);
	dmu_tx_commit(tx);

	vdev_rebuild_log_notify(spa, vd, ESC_ZFS_RESILVER_START);
}

/*
 * Update the on-disk state to completed when a rebuild finishes.
 */
static void
vdev_rebuild_complete_sync(void *arg, dmu_tx_t *tx)
{
	int vdev_id = (uintptr_t)arg;
	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
	vdev_t *vd = vdev_lookup_top(spa, vdev_id);
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;

	mutex_enter(&vd->vdev_rebuild_lock);
	vrp->vrp_rebuild_state = VDEV_REBUILD_COMPLETE;
	vrp->vrp_end_time = gethrestime_sec();

	VERIFY0(zap_update(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap,
	    VDEV_TOP_ZAP_VDEV_REBUILD_PHYS, sizeof (uint64_t),
	    REBUILD_PHYS_ENTRIES, vrp, tx));

	vdev_dtl_reassess(vd, tx->tx_txg, vrp->vrp_max_txg, B_TRUE, B_TRUE);
	spa_feature_decr(vd->vdev_spa, SPA_FEATURE_DEVICE_REBUILD, tx);

	spa_history_log_internal(spa, "rebuild",  tx,
	    "vdev_id=%llu vdev_guid=%llu complete",
	    (u_longlong_t)vd->vdev_id, (u_longlong_t)vd->vdev_guid);
	vdev_rebuild_log_notify(spa, vd, ESC_ZFS_RESILVER_FINISH);

	/* Handles detaching of spares */
	spa_async_request(spa, SPA_ASYNC_REBUILD_DONE);
	vd->vdev_rebuilding = B_FALSE;
	mutex_exit(&vd->vdev_rebuild_lock);

	/*
	 * While we're in syncing context take the opportunity to
	 * setup the scrub when there are no more active rebuilds.
	 */
	if (!vdev_rebuild_active(spa->spa_root_vdev) &&
	    zfs_rebuild_scrub_enabled) {
		pool_scan_func_t func = POOL_SCAN_SCRUB;
		dsl_scan_setup_sync(&func, tx);
	}

	cv_broadcast(&vd->vdev_rebuild_cv);

	/* Clear recent error events (i.e. duplicate events tracking) */
	zfs_ereport_clear(spa, NULL);
}

/*
 * Update the on-disk state to canceled when a rebuild finishes.
 */
static void
vdev_rebuild_cancel_sync(void *arg, dmu_tx_t *tx)
{
	int vdev_id = (uintptr_t)arg;
	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
	vdev_t *vd = vdev_lookup_top(spa, vdev_id);
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;

	mutex_enter(&vd->vdev_rebuild_lock);
	vrp->vrp_rebuild_state = VDEV_REBUILD_CANCELED;
	vrp->vrp_end_time = gethrestime_sec();

	VERIFY0(zap_update(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap,
	    VDEV_TOP_ZAP_VDEV_REBUILD_PHYS, sizeof (uint64_t),
	    REBUILD_PHYS_ENTRIES, vrp, tx));

	spa_feature_decr(vd->vdev_spa, SPA_FEATURE_DEVICE_REBUILD, tx);

	spa_history_log_internal(spa, "rebuild",  tx,
	    "vdev_id=%llu vdev_guid=%llu canceled",
	    (u_longlong_t)vd->vdev_id, (u_longlong_t)vd->vdev_guid);
	vdev_rebuild_log_notify(spa, vd, ESC_ZFS_RESILVER_FINISH);

	vd->vdev_rebuild_cancel_wanted = B_FALSE;
	vd->vdev_rebuilding = B_FALSE;
	mutex_exit(&vd->vdev_rebuild_lock);

	spa_notify_waiters(spa);
	cv_broadcast(&vd->vdev_rebuild_cv);
}

/*
 * Resets the progress of a running rebuild.  This will occur when a new
 * vdev is added to rebuild.
 */
static void
vdev_rebuild_reset_sync(void *arg, dmu_tx_t *tx)
{
	int vdev_id = (uintptr_t)arg;
	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
	vdev_t *vd = vdev_lookup_top(spa, vdev_id);
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;

	mutex_enter(&vd->vdev_rebuild_lock);

	ASSERT(vrp->vrp_rebuild_state == VDEV_REBUILD_ACTIVE);
	ASSERT3P(vd->vdev_rebuild_thread, ==, NULL);

	vrp->vrp_last_offset = 0;
	vrp->vrp_min_txg = 0;
	vrp->vrp_max_txg = dmu_tx_get_txg(tx);
	vrp->vrp_bytes_scanned = 0;
	vrp->vrp_bytes_issued = 0;
	vrp->vrp_bytes_rebuilt = 0;
	vrp->vrp_bytes_est = 0;
	vrp->vrp_scan_time_ms = 0;
	vr->vr_prev_scan_time_ms = 0;

	/* See vdev_rebuild_initiate_sync comment */
	VERIFY(vdev_resilver_needed(vd, &vrp->vrp_min_txg, &vrp->vrp_max_txg));

	VERIFY0(zap_update(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap,
	    VDEV_TOP_ZAP_VDEV_REBUILD_PHYS, sizeof (uint64_t),
	    REBUILD_PHYS_ENTRIES, vrp, tx));

	spa_history_log_internal(spa, "rebuild",  tx,
	    "vdev_id=%llu vdev_guid=%llu reset",
	    (u_longlong_t)vd->vdev_id, (u_longlong_t)vd->vdev_guid);

	vd->vdev_rebuild_reset_wanted = B_FALSE;
	ASSERT(vd->vdev_rebuilding);

	vd->vdev_rebuild_thread = thread_create(NULL, 0,
	    vdev_rebuild_thread, vd, 0, &p0, TS_RUN, maxclsyspri);

	mutex_exit(&vd->vdev_rebuild_lock);
}

/*
 * Clear the last rebuild status.
 */
void
vdev_rebuild_clear_sync(void *arg, dmu_tx_t *tx)
{
	int vdev_id = (uintptr_t)arg;
	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
	vdev_t *vd = vdev_lookup_top(spa, vdev_id);
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
	objset_t *mos = spa_meta_objset(spa);

	mutex_enter(&vd->vdev_rebuild_lock);

	if (!spa_feature_is_enabled(spa, SPA_FEATURE_DEVICE_REBUILD) ||
	    vrp->vrp_rebuild_state == VDEV_REBUILD_ACTIVE) {
		mutex_exit(&vd->vdev_rebuild_lock);
		return;
	}

	clear_rebuild_bytes(vd);
	bzero(vrp, sizeof (uint64_t) * REBUILD_PHYS_ENTRIES);

	if (vd->vdev_top_zap != 0 && zap_contains(mos, vd->vdev_top_zap,
	    VDEV_TOP_ZAP_VDEV_REBUILD_PHYS) == 0) {
		VERIFY0(zap_update(mos, vd->vdev_top_zap,
		    VDEV_TOP_ZAP_VDEV_REBUILD_PHYS, sizeof (uint64_t),
		    REBUILD_PHYS_ENTRIES, vrp, tx));
	}

	mutex_exit(&vd->vdev_rebuild_lock);
}

/*
 * The zio_done_func_t callback for each rebuild I/O issued.  It's responsible
 * for updating the rebuild stats and limiting the number of in flight I/Os.
 */
static void
vdev_rebuild_cb(zio_t *zio)
{
	vdev_rebuild_t *vr = zio->io_private;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
	vdev_t *vd = vr->vr_top_vdev;

	mutex_enter(&vr->vr_io_lock);
	if (zio->io_error == ENXIO && !vdev_writeable(vd)) {
		/*
		 * The I/O failed because the top-level vdev was unavailable.
		 * Attempt to roll back to the last completed offset, in order
		 * resume from the correct location if the pool is resumed.
		 * (This works because spa_sync waits on spa_txg_zio before
		 * it runs sync tasks.)
		 */
		uint64_t *off = &vr->vr_scan_offset[zio->io_txg & TXG_MASK];
		*off = MIN(*off, zio->io_offset);
	} else if (zio->io_error) {
		vrp->vrp_errors++;
	}

	abd_free(zio->io_abd);

	ASSERT3U(vr->vr_bytes_inflight, >, 0);
	vr->vr_bytes_inflight -= zio->io_size;
	cv_broadcast(&vr->vr_io_cv);
	mutex_exit(&vr->vr_io_lock);

	spa_config_exit(vd->vdev_spa, SCL_STATE_ALL, vd);
}

/*
 * Initialize a block pointer that can be used to read the given segment
 * for sequential rebuild.
 */
static void
vdev_rebuild_blkptr_init(blkptr_t *bp, vdev_t *vd, uint64_t start,
    uint64_t asize)
{
	ASSERT(vd->vdev_ops == &vdev_draid_ops ||
	    vd->vdev_ops == &vdev_mirror_ops ||
	    vd->vdev_ops == &vdev_replacing_ops ||
	    vd->vdev_ops == &vdev_spare_ops);

	uint64_t psize = vd->vdev_ops == &vdev_draid_ops ?
	    vdev_draid_asize_to_psize(vd, asize) : asize;

	BP_ZERO(bp);

	DVA_SET_VDEV(&bp->blk_dva[0], vd->vdev_id);
	DVA_SET_OFFSET(&bp->blk_dva[0], start);
	DVA_SET_GANG(&bp->blk_dva[0], 0);
	DVA_SET_ASIZE(&bp->blk_dva[0], asize);

	BP_SET_BIRTH(bp, TXG_INITIAL, TXG_INITIAL);
	BP_SET_LSIZE(bp, psize);
	BP_SET_PSIZE(bp, psize);
	BP_SET_COMPRESS(bp, ZIO_COMPRESS_OFF);
	BP_SET_CHECKSUM(bp, ZIO_CHECKSUM_OFF);
	BP_SET_TYPE(bp, DMU_OT_NONE);
	BP_SET_LEVEL(bp, 0);
	BP_SET_DEDUP(bp, 0);
	BP_SET_BYTEORDER(bp, ZFS_HOST_BYTEORDER);
}

/*
 * Issues a rebuild I/O and takes care of rate limiting the number of queued
 * rebuild I/Os.  The provided start and size must be properly aligned for the
 * top-level vdev type being rebuilt.
 */
static int
vdev_rebuild_range(vdev_rebuild_t *vr, uint64_t start, uint64_t size)
{
	uint64_t ms_id __maybe_unused = vr->vr_scan_msp->ms_id;
	vdev_t *vd = vr->vr_top_vdev;
	spa_t *spa = vd->vdev_spa;
	blkptr_t blk;

	ASSERT3U(ms_id, ==, start >> vd->vdev_ms_shift);
	ASSERT3U(ms_id, ==, (start + size - 1) >> vd->vdev_ms_shift);

	vr->vr_pass_bytes_scanned += size;
	vr->vr_rebuild_phys.vrp_bytes_scanned += size;

	/*
	 * Rebuild the data in this range by constructing a special block
	 * pointer.  It has no relation to any existing blocks in the pool.
	 * However, by disabling checksum verification and issuing a scrub IO
	 * we can reconstruct and repair any children with missing data.
	 */
	vdev_rebuild_blkptr_init(&blk, vd, start, size);
	uint64_t psize = BP_GET_PSIZE(&blk);

	if (!vdev_dtl_need_resilver(vd, &blk.blk_dva[0], psize, TXG_UNKNOWN))
		return (0);

	mutex_enter(&vr->vr_io_lock);

	/* Limit in flight rebuild I/Os */
	while (vr->vr_bytes_inflight >= vr->vr_bytes_inflight_max)
		cv_wait(&vr->vr_io_cv, &vr->vr_io_lock);

	vr->vr_bytes_inflight += psize;
	mutex_exit(&vr->vr_io_lock);

	dmu_tx_t *tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir);
	VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
	uint64_t txg = dmu_tx_get_txg(tx);

	spa_config_enter(spa, SCL_STATE_ALL, vd, RW_READER);
	mutex_enter(&vd->vdev_rebuild_lock);

	/* This is the first I/O for this txg. */
	if (vr->vr_scan_offset[txg & TXG_MASK] == 0) {
		vr->vr_scan_offset[txg & TXG_MASK] = start;
		dsl_sync_task_nowait(spa_get_dsl(spa),
		    vdev_rebuild_update_sync,
		    (void *)(uintptr_t)vd->vdev_id, tx);
	}

	/* When exiting write out our progress. */
	if (vdev_rebuild_should_stop(vd)) {
		mutex_enter(&vr->vr_io_lock);
		vr->vr_bytes_inflight -= psize;
		mutex_exit(&vr->vr_io_lock);
		spa_config_exit(vd->vdev_spa, SCL_STATE_ALL, vd);
		mutex_exit(&vd->vdev_rebuild_lock);
		dmu_tx_commit(tx);
		return (SET_ERROR(EINTR));
	}
	mutex_exit(&vd->vdev_rebuild_lock);
	dmu_tx_commit(tx);

	vr->vr_scan_offset[txg & TXG_MASK] = start + size;
	vr->vr_pass_bytes_issued += size;
	vr->vr_rebuild_phys.vrp_bytes_issued += size;

	zio_nowait(zio_read(spa->spa_txg_zio[txg & TXG_MASK], spa, &blk,
	    abd_alloc(psize, B_FALSE), psize, vdev_rebuild_cb, vr,
	    ZIO_PRIORITY_REBUILD, ZIO_FLAG_RAW | ZIO_FLAG_CANFAIL |
	    ZIO_FLAG_RESILVER, NULL));

	return (0);
}

/*
 * Issues rebuild I/Os for all ranges in the provided vr->vr_tree range tree.
 */
static int
vdev_rebuild_ranges(vdev_rebuild_t *vr)
{
	vdev_t *vd = vr->vr_top_vdev;
	zfs_btree_t *t = &vr->vr_scan_tree->rt_root;
	zfs_btree_index_t idx;
	int error;

	for (range_seg_t *rs = zfs_btree_first(t, &idx); rs != NULL;
	    rs = zfs_btree_next(t, &idx, &idx)) {
		uint64_t start = rs_get_start(rs, vr->vr_scan_tree);
		uint64_t size = rs_get_end(rs, vr->vr_scan_tree) - start;

		/*
		 * zfs_scan_suspend_progress can be set to disable rebuild
		 * progress for testing.  See comment in dsl_scan_sync().
		 */
		while (zfs_scan_suspend_progress &&
		    !vdev_rebuild_should_stop(vd)) {
			delay(hz);
		}

		while (size > 0) {
			uint64_t chunk_size;

			/*
			 * Split range into legally-sized logical chunks
			 * given the constraints of the top-level vdev
			 * being rebuilt (dRAID or mirror).
			 */
			ASSERT3P(vd->vdev_ops, !=, NULL);
			chunk_size = vd->vdev_ops->vdev_op_rebuild_asize(vd,
			    start, size, zfs_rebuild_max_segment);

			error = vdev_rebuild_range(vr, start, chunk_size);
			if (error != 0)
				return (error);

			size -= chunk_size;
			start += chunk_size;
		}
	}

	return (0);
}

/*
 * Calculates the estimated capacity which remains to be scanned.  Since
 * we traverse the pool in metaslab order only allocated capacity beyond
 * the vrp_last_offset need be considered.  All lower offsets must have
 * already been rebuilt and are thus already included in vrp_bytes_scanned.
 */
static void
vdev_rebuild_update_bytes_est(vdev_t *vd, uint64_t ms_id)
{
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
	uint64_t bytes_est = vrp->vrp_bytes_scanned;

	if (vrp->vrp_last_offset < vd->vdev_ms[ms_id]->ms_start)
		return;

	for (uint64_t i = ms_id; i < vd->vdev_ms_count; i++) {
		metaslab_t *msp = vd->vdev_ms[i];

		mutex_enter(&msp->ms_lock);
		bytes_est += metaslab_allocated_space(msp);
		mutex_exit(&msp->ms_lock);
	}

	vrp->vrp_bytes_est = bytes_est;
}

/*
 * Load from disk the top-level vdev's rebuild information.
 */
int
vdev_rebuild_load(vdev_t *vd)
{
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
	spa_t *spa = vd->vdev_spa;
	int err = 0;

	mutex_enter(&vd->vdev_rebuild_lock);
	vd->vdev_rebuilding = B_FALSE;

	if (!spa_feature_is_enabled(spa, SPA_FEATURE_DEVICE_REBUILD)) {
		bzero(vrp, sizeof (uint64_t) * REBUILD_PHYS_ENTRIES);
		mutex_exit(&vd->vdev_rebuild_lock);
		return (SET_ERROR(ENOTSUP));
	}

	ASSERT(vd->vdev_top == vd);

	err = zap_lookup(spa->spa_meta_objset, vd->vdev_top_zap,
	    VDEV_TOP_ZAP_VDEV_REBUILD_PHYS, sizeof (uint64_t),
	    REBUILD_PHYS_ENTRIES, vrp);

	/*
	 * A missing or damaged VDEV_TOP_ZAP_VDEV_REBUILD_PHYS should
	 * not prevent a pool from being imported.  Clear the rebuild
	 * status allowing a new resilver/rebuild to be started.
	 */
	if (err == ENOENT || err == EOVERFLOW || err == ECKSUM) {
		bzero(vrp, sizeof (uint64_t) * REBUILD_PHYS_ENTRIES);
	} else if (err) {
		mutex_exit(&vd->vdev_rebuild_lock);
		return (err);
	}

	vr->vr_prev_scan_time_ms = vrp->vrp_scan_time_ms;
	vr->vr_top_vdev = vd;

	mutex_exit(&vd->vdev_rebuild_lock);

	return (0);
}

/*
 * Each scan thread is responsible for rebuilding a top-level vdev.  The
 * rebuild progress in tracked on-disk in VDEV_TOP_ZAP_VDEV_REBUILD_PHYS.
 */
static void
vdev_rebuild_thread(void *arg)
{
	vdev_t *vd = arg;
	spa_t *spa = vd->vdev_spa;
	int error = 0;

	/*
	 * If there's a scrub in process request that it be stopped.  This
	 * is not required for a correct rebuild, but we do want rebuilds to
	 * emulate the resilver behavior as much as possible.
	 */
	dsl_pool_t *dsl = spa_get_dsl(spa);
	if (dsl_scan_scrubbing(dsl))
		dsl_scan_cancel(dsl);

	spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
	mutex_enter(&vd->vdev_rebuild_lock);

	ASSERT3P(vd->vdev_top, ==, vd);
	ASSERT3P(vd->vdev_rebuild_thread, !=, NULL);
	ASSERT(vd->vdev_rebuilding);
	ASSERT(spa_feature_is_active(spa, SPA_FEATURE_DEVICE_REBUILD));
	ASSERT3B(vd->vdev_rebuild_cancel_wanted, ==, B_FALSE);
	ASSERT3B(vd->vdev_rebuild_reset_wanted, ==, B_FALSE);

	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
	vr->vr_top_vdev = vd;
	vr->vr_scan_msp = NULL;
	vr->vr_scan_tree = range_tree_create(NULL, RANGE_SEG64, NULL, 0, 0);
	mutex_init(&vr->vr_io_lock, NULL, MUTEX_DEFAULT, NULL);
	cv_init(&vr->vr_io_cv, NULL, CV_DEFAULT, NULL);

	vr->vr_pass_start_time = gethrtime();
	vr->vr_pass_bytes_scanned = 0;
	vr->vr_pass_bytes_issued = 0;

	vr->vr_bytes_inflight_max = MAX(1ULL << 20,
	    zfs_rebuild_vdev_limit * vd->vdev_children);

	uint64_t update_est_time = gethrtime();
	vdev_rebuild_update_bytes_est(vd, 0);

	clear_rebuild_bytes(vr->vr_top_vdev);

	mutex_exit(&vd->vdev_rebuild_lock);

	/*
	 * Systematically walk the metaslabs and issue rebuild I/Os for
	 * all ranges in the allocated space map.
	 */
	for (uint64_t i = 0; i < vd->vdev_ms_count; i++) {
		metaslab_t *msp = vd->vdev_ms[i];
		vr->vr_scan_msp = msp;

		/*
		 * Removal of vdevs from the vdev tree may eliminate the need
		 * for the rebuild, in which case it should be canceled.  The
		 * vdev_rebuild_cancel_wanted flag is set until the sync task
		 * completes.  This may be after the rebuild thread exits.
		 */
		if (vdev_rebuild_should_cancel(vd)) {
			vd->vdev_rebuild_cancel_wanted = B_TRUE;
			error = EINTR;
			break;
		}

		ASSERT0(range_tree_space(vr->vr_scan_tree));

		/* Disable any new allocations to this metaslab */
		spa_config_exit(spa, SCL_CONFIG, FTAG);
		metaslab_disable(msp);

		mutex_enter(&msp->ms_sync_lock);
		mutex_enter(&msp->ms_lock);

		/*
		 * If there are outstanding allocations wait for them to be
		 * synced.  This is needed to ensure all allocated ranges are
		 * on disk and therefore will be rebuilt.
		 */
		for (int j = 0; j < TXG_SIZE; j++) {
			if (range_tree_space(msp->ms_allocating[j])) {
				mutex_exit(&msp->ms_lock);
				mutex_exit(&msp->ms_sync_lock);
				txg_wait_synced(dsl, 0);
				mutex_enter(&msp->ms_sync_lock);
				mutex_enter(&msp->ms_lock);
				break;
			}
		}

		/*
		 * When a metaslab has been allocated from read its allocated
		 * ranges from the space map object into the vr_scan_tree.
		 * Then add inflight / unflushed ranges and remove inflight /
		 * unflushed frees.  This is the minimum range to be rebuilt.
		 */
		if (msp->ms_sm != NULL) {
			VERIFY0(space_map_load(msp->ms_sm,
			    vr->vr_scan_tree, SM_ALLOC));

			for (int i = 0; i < TXG_SIZE; i++) {
				ASSERT0(range_tree_space(
				    msp->ms_allocating[i]));
			}

			range_tree_walk(msp->ms_unflushed_allocs,
			    range_tree_add, vr->vr_scan_tree);
			range_tree_walk(msp->ms_unflushed_frees,
			    range_tree_remove, vr->vr_scan_tree);

			/*
			 * Remove ranges which have already been rebuilt based
			 * on the last offset.  This can happen when restarting
			 * a scan after exporting and re-importing the pool.
			 */
			range_tree_clear(vr->vr_scan_tree, 0,
			    vrp->vrp_last_offset);
		}

		mutex_exit(&msp->ms_lock);
		mutex_exit(&msp->ms_sync_lock);

		/*
		 * To provide an accurate estimate re-calculate the estimated
		 * size every 5 minutes to account for recent allocations and
		 * frees made to space maps which have not yet been rebuilt.
		 */
		if (gethrtime() > update_est_time + SEC2NSEC(300)) {
			update_est_time = gethrtime();
			vdev_rebuild_update_bytes_est(vd, i);
		}

		/*
		 * Walk the allocated space map and issue the rebuild I/O.
		 */
		error = vdev_rebuild_ranges(vr);
		range_tree_vacate(vr->vr_scan_tree, NULL, NULL);

		spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
		metaslab_enable(msp, B_FALSE, B_FALSE);

		if (error != 0)
			break;
	}

	range_tree_destroy(vr->vr_scan_tree);
	spa_config_exit(spa, SCL_CONFIG, FTAG);

	/* Wait for any remaining rebuild I/O to complete */
	mutex_enter(&vr->vr_io_lock);
	while (vr->vr_bytes_inflight > 0)
		cv_wait(&vr->vr_io_cv, &vr->vr_io_lock);

	mutex_exit(&vr->vr_io_lock);

	mutex_destroy(&vr->vr_io_lock);
	cv_destroy(&vr->vr_io_cv);

	spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

	dsl_pool_t *dp = spa_get_dsl(spa);
	dmu_tx_t *tx = dmu_tx_create_dd(dp->dp_mos_dir);
	VERIFY0(dmu_tx_assign(tx, TXG_WAIT));

	mutex_enter(&vd->vdev_rebuild_lock);
	if (error == 0) {
		/*
		 * After a successful rebuild clear the DTLs of all ranges
		 * which were missing when the rebuild was started.  These
		 * ranges must have been rebuilt as a consequence of rebuilding
		 * all allocated space.  Note that unlike a scrub or resilver
		 * the rebuild operation will reconstruct data only referenced
		 * by a pool checkpoint.  See the dsl_scan_done() comments.
		 */
		dsl_sync_task_nowait(dp, vdev_rebuild_complete_sync,
		    (void *)(uintptr_t)vd->vdev_id, tx);
	} else if (vd->vdev_rebuild_cancel_wanted) {
		/*
		 * The rebuild operation was canceled.  This will occur when
		 * a device participating in the rebuild is detached.
		 */
		dsl_sync_task_nowait(dp, vdev_rebuild_cancel_sync,
		    (void *)(uintptr_t)vd->vdev_id, tx);
	} else if (vd->vdev_rebuild_reset_wanted) {
		/*
		 * Reset the running rebuild without canceling and restarting
		 * it.  This will occur when a new device is attached and must
		 * participate in the rebuild.
		 */
		dsl_sync_task_nowait(dp, vdev_rebuild_reset_sync,
		    (void *)(uintptr_t)vd->vdev_id, tx);
	} else {
		/*
		 * The rebuild operation should be suspended.  This may occur
		 * when detaching a child vdev or when exporting the pool.  The
		 * rebuild is left in the active state so it will be resumed.
		 */
		ASSERT(vrp->vrp_rebuild_state == VDEV_REBUILD_ACTIVE);
		vd->vdev_rebuilding = B_FALSE;
	}

	dmu_tx_commit(tx);

	vd->vdev_rebuild_thread = NULL;
	mutex_exit(&vd->vdev_rebuild_lock);
	spa_config_exit(spa, SCL_CONFIG, FTAG);

	cv_broadcast(&vd->vdev_rebuild_cv);

	thread_exit();
}

/*
 * Returns B_TRUE if any top-level vdev are rebuilding.
 */
boolean_t
vdev_rebuild_active(vdev_t *vd)
{
	spa_t *spa = vd->vdev_spa;
	boolean_t ret = B_FALSE;

	if (vd == spa->spa_root_vdev) {
		for (uint64_t i = 0; i < vd->vdev_children; i++) {
			ret = vdev_rebuild_active(vd->vdev_child[i]);
			if (ret)
				return (ret);
		}
	} else if (vd->vdev_top_zap != 0) {
		vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
		vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;

		mutex_enter(&vd->vdev_rebuild_lock);
		ret = (vrp->vrp_rebuild_state == VDEV_REBUILD_ACTIVE);
		mutex_exit(&vd->vdev_rebuild_lock);
	}

	return (ret);
}

/*
 * Start a rebuild operation.  The rebuild may be restarted when the
 * top-level vdev is currently actively rebuilding.
 */
void
vdev_rebuild(vdev_t *vd)
{
	vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
	vdev_rebuild_phys_t *vrp __maybe_unused = &vr->vr_rebuild_phys;

	ASSERT(vd->vdev_top == vd);
	ASSERT(vdev_is_concrete(vd));
	ASSERT(!vd->vdev_removing);
	ASSERT(spa_feature_is_enabled(vd->vdev_spa,
	    SPA_FEATURE_DEVICE_REBUILD));

	mutex_enter(&vd->vdev_rebuild_lock);
	if (vd->vdev_rebuilding) {
		ASSERT3U(vrp->vrp_rebuild_state, ==, VDEV_REBUILD_ACTIVE);

		/*
		 * Signal a running rebuild operation that it should restart
		 * from the beginning because a new device was attached.  The
		 * vdev_rebuild_reset_wanted flag is set until the sync task
		 * completes.  This may be after the rebuild thread exits.
		 */
		if (!vd->vdev_rebuild_reset_wanted)
			vd->vdev_rebuild_reset_wanted = B_TRUE;
	} else {
		vdev_rebuild_initiate(vd);
	}
	mutex_exit(&vd->vdev_rebuild_lock);
}

static void
vdev_rebuild_restart_impl(vdev_t *vd)
{
	spa_t *spa = vd->vdev_spa;

	if (vd == spa->spa_root_vdev) {
		for (uint64_t i = 0; i < vd->vdev_children; i++)
			vdev_rebuild_restart_impl(vd->vdev_child[i]);

	} else if (vd->vdev_top_zap != 0) {
		vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
		vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;

		mutex_enter(&vd->vdev_rebuild_lock);
		if (vrp->vrp_rebuild_state == VDEV_REBUILD_ACTIVE &&
		    vdev_writeable(vd) && !vd->vdev_rebuilding) {
			ASSERT(spa_feature_is_active(spa,
			    SPA_FEATURE_DEVICE_REBUILD));
			vd->vdev_rebuilding = B_TRUE;
			vd->vdev_rebuild_thread = thread_create(NULL, 0,
			    vdev_rebuild_thread, vd, 0, &p0, TS_RUN,
			    maxclsyspri);
		}
		mutex_exit(&vd->vdev_rebuild_lock);
	}
}

/*
 * Conditionally restart all of the vdev_rebuild_thread's for a pool.  The
 * feature flag must be active and the rebuild in the active state.   This
 * cannot be used to start a new rebuild.
 */
void
vdev_rebuild_restart(spa_t *spa)
{
	ASSERT(MUTEX_HELD(&spa_namespace_lock));

	vdev_rebuild_restart_impl(spa->spa_root_vdev);
}

/*
 * Stop and wait for all of the vdev_rebuild_thread's associated with the
 * vdev tree provide to be terminated (canceled or stopped).
 */
void
vdev_rebuild_stop_wait(vdev_t *vd)
{
	spa_t *spa = vd->vdev_spa;

	ASSERT(MUTEX_HELD(&spa_namespace_lock));

	if (vd == spa->spa_root_vdev) {
		for (uint64_t i = 0; i < vd->vdev_children; i++)
			vdev_rebuild_stop_wait(vd->vdev_child[i]);

	} else if (vd->vdev_top_zap != 0) {
		ASSERT(vd == vd->vdev_top);

		mutex_enter(&vd->vdev_rebuild_lock);
		if (vd->vdev_rebuild_thread != NULL) {
			vd->vdev_rebuild_exit_wanted = B_TRUE;
			while (vd->vdev_rebuilding) {
				cv_wait(&vd->vdev_rebuild_cv,
				    &vd->vdev_rebuild_lock);
			}
			vd->vdev_rebuild_exit_wanted = B_FALSE;
		}
		mutex_exit(&vd->vdev_rebuild_lock);
	}
}

/*
 * Stop all rebuild operations but leave them in the active state so they
 * will be resumed when importing the pool.
 */
void
vdev_rebuild_stop_all(spa_t *spa)
{
	vdev_rebuild_stop_wait(spa->spa_root_vdev);
}

/*
 * Rebuild statistics reported per top-level vdev.
 */
int
vdev_rebuild_get_stats(vdev_t *tvd, vdev_rebuild_stat_t *vrs)
{
	spa_t *spa = tvd->vdev_spa;

	if (!spa_feature_is_enabled(spa, SPA_FEATURE_DEVICE_REBUILD))
		return (SET_ERROR(ENOTSUP));

	if (tvd != tvd->vdev_top || tvd->vdev_top_zap == 0)
		return (SET_ERROR(EINVAL));

	int error = zap_contains(spa_meta_objset(spa),
	    tvd->vdev_top_zap, VDEV_TOP_ZAP_VDEV_REBUILD_PHYS);

	if (error == ENOENT) {
		bzero(vrs, sizeof (vdev_rebuild_stat_t));
		vrs->vrs_state = VDEV_REBUILD_NONE;
		error = 0;
	} else if (error == 0) {
		vdev_rebuild_t *vr = &tvd->vdev_rebuild_config;
		vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;

		mutex_enter(&tvd->vdev_rebuild_lock);
		vrs->vrs_state = vrp->vrp_rebuild_state;
		vrs->vrs_start_time = vrp->vrp_start_time;
		vrs->vrs_end_time = vrp->vrp_end_time;
		vrs->vrs_scan_time_ms = vrp->vrp_scan_time_ms;
		vrs->vrs_bytes_scanned = vrp->vrp_bytes_scanned;
		vrs->vrs_bytes_issued = vrp->vrp_bytes_issued;
		vrs->vrs_bytes_rebuilt = vrp->vrp_bytes_rebuilt;
		vrs->vrs_bytes_est = vrp->vrp_bytes_est;
		vrs->vrs_errors = vrp->vrp_errors;
		vrs->vrs_pass_time_ms = NSEC2MSEC(gethrtime() -
		    vr->vr_pass_start_time);
		vrs->vrs_pass_bytes_scanned = vr->vr_pass_bytes_scanned;
		vrs->vrs_pass_bytes_issued = vr->vr_pass_bytes_issued;
		mutex_exit(&tvd->vdev_rebuild_lock);
	}

	return (error);
}

/* BEGIN CSTYLED */
ZFS_MODULE_PARAM(zfs, zfs_, rebuild_max_segment, ULONG, ZMOD_RW,
	"Max segment size in bytes of rebuild reads");

ZFS_MODULE_PARAM(zfs, zfs_, rebuild_vdev_limit, ULONG, ZMOD_RW,
	"Max bytes in flight per leaf vdev for sequential resilvers");

ZFS_MODULE_PARAM(zfs, zfs_, rebuild_scrub_enabled, INT, ZMOD_RW,
	"Automatically scrub after sequential resilver completes");
/* END CSTYLED */