Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
  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
// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2018 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_btree.h"
#include "xfs_log_format.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_inode.h"
#include "xfs_alloc.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc.h"
#include "xfs_ialloc_btree.h"
#include "xfs_rmap.h"
#include "xfs_rmap_btree.h"
#include "xfs_refcount_btree.h"
#include "xfs_extent_busy.h"
#include "xfs_ag_resv.h"
#include "xfs_quota.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/trace.h"
#include "scrub/repair.h"
#include "scrub/bitmap.h"

/*
 * Attempt to repair some metadata, if the metadata is corrupt and userspace
 * told us to fix it.  This function returns -EAGAIN to mean "re-run scrub",
 * and will set *fixed to true if it thinks it repaired anything.
 */
int
xrep_attempt(
	struct xfs_inode	*ip,
	struct xfs_scrub	*sc)
{
	int			error = 0;

	trace_xrep_attempt(ip, sc->sm, error);

	xchk_ag_btcur_free(&sc->sa);

	/* Repair whatever's broken. */
	ASSERT(sc->ops->repair);
	error = sc->ops->repair(sc);
	trace_xrep_done(ip, sc->sm, error);
	switch (error) {
	case 0:
		/*
		 * Repair succeeded.  Commit the fixes and perform a second
		 * scrub so that we can tell userspace if we fixed the problem.
		 */
		sc->sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
		sc->flags |= XREP_ALREADY_FIXED;
		return -EAGAIN;
	case -EDEADLOCK:
	case -EAGAIN:
		/* Tell the caller to try again having grabbed all the locks. */
		if (!(sc->flags & XCHK_TRY_HARDER)) {
			sc->flags |= XCHK_TRY_HARDER;
			return -EAGAIN;
		}
		/*
		 * We tried harder but still couldn't grab all the resources
		 * we needed to fix it.  The corruption has not been fixed,
		 * so report back to userspace.
		 */
		return -EFSCORRUPTED;
	default:
		return error;
	}
}

/*
 * Complain about unfixable problems in the filesystem.  We don't log
 * corruptions when IFLAG_REPAIR wasn't set on the assumption that the driver
 * program is xfs_scrub, which will call back with IFLAG_REPAIR set if the
 * administrator isn't running xfs_scrub in no-repairs mode.
 *
 * Use this helper function because _ratelimited silently declares a static
 * structure to track rate limiting information.
 */
void
xrep_failure(
	struct xfs_mount	*mp)
{
	xfs_alert_ratelimited(mp,
"Corruption not fixed during online repair.  Unmount and run xfs_repair.");
}

/*
 * Repair probe -- userspace uses this to probe if we're willing to repair a
 * given mountpoint.
 */
int
xrep_probe(
	struct xfs_scrub	*sc)
{
	int			error = 0;

	if (xchk_should_terminate(sc, &error))
		return error;

	return 0;
}

/*
 * Roll a transaction, keeping the AG headers locked and reinitializing
 * the btree cursors.
 */
int
xrep_roll_ag_trans(
	struct xfs_scrub	*sc)
{
	int			error;

	/* Keep the AG header buffers locked so we can keep going. */
	if (sc->sa.agi_bp)
		xfs_trans_bhold(sc->tp, sc->sa.agi_bp);
	if (sc->sa.agf_bp)
		xfs_trans_bhold(sc->tp, sc->sa.agf_bp);
	if (sc->sa.agfl_bp)
		xfs_trans_bhold(sc->tp, sc->sa.agfl_bp);

	/*
	 * Roll the transaction.  We still own the buffer and the buffer lock
	 * regardless of whether or not the roll succeeds.  If the roll fails,
	 * the buffers will be released during teardown on our way out of the
	 * kernel.  If it succeeds, we join them to the new transaction and
	 * move on.
	 */
	error = xfs_trans_roll(&sc->tp);
	if (error)
		return error;

	/* Join AG headers to the new transaction. */
	if (sc->sa.agi_bp)
		xfs_trans_bjoin(sc->tp, sc->sa.agi_bp);
	if (sc->sa.agf_bp)
		xfs_trans_bjoin(sc->tp, sc->sa.agf_bp);
	if (sc->sa.agfl_bp)
		xfs_trans_bjoin(sc->tp, sc->sa.agfl_bp);

	return 0;
}

/*
 * Does the given AG have enough space to rebuild a btree?  Neither AG
 * reservation can be critical, and we must have enough space (factoring
 * in AG reservations) to construct a whole btree.
 */
bool
xrep_ag_has_space(
	struct xfs_perag	*pag,
	xfs_extlen_t		nr_blocks,
	enum xfs_ag_resv_type	type)
{
	return  !xfs_ag_resv_critical(pag, XFS_AG_RESV_RMAPBT) &&
		!xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA) &&
		pag->pagf_freeblks > xfs_ag_resv_needed(pag, type) + nr_blocks;
}

/*
 * Figure out how many blocks to reserve for an AG repair.  We calculate the
 * worst case estimate for the number of blocks we'd need to rebuild one of
 * any type of per-AG btree.
 */
xfs_extlen_t
xrep_calc_ag_resblks(
	struct xfs_scrub		*sc)
{
	struct xfs_mount		*mp = sc->mp;
	struct xfs_scrub_metadata	*sm = sc->sm;
	struct xfs_perag		*pag;
	struct xfs_buf			*bp;
	xfs_agino_t			icount = NULLAGINO;
	xfs_extlen_t			aglen = NULLAGBLOCK;
	xfs_extlen_t			usedlen;
	xfs_extlen_t			freelen;
	xfs_extlen_t			bnobt_sz;
	xfs_extlen_t			inobt_sz;
	xfs_extlen_t			rmapbt_sz;
	xfs_extlen_t			refcbt_sz;
	int				error;

	if (!(sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
		return 0;

	pag = xfs_perag_get(mp, sm->sm_agno);
	if (pag->pagi_init) {
		/* Use in-core icount if possible. */
		icount = pag->pagi_count;
	} else {
		/* Try to get the actual counters from disk. */
		error = xfs_ialloc_read_agi(mp, NULL, sm->sm_agno, &bp);
		if (!error) {
			icount = pag->pagi_count;
			xfs_buf_relse(bp);
		}
	}

	/* Now grab the block counters from the AGF. */
	error = xfs_alloc_read_agf(mp, NULL, sm->sm_agno, 0, &bp);
	if (!error) {
		aglen = be32_to_cpu(XFS_BUF_TO_AGF(bp)->agf_length);
		freelen = be32_to_cpu(XFS_BUF_TO_AGF(bp)->agf_freeblks);
		usedlen = aglen - freelen;
		xfs_buf_relse(bp);
	}
	xfs_perag_put(pag);

	/* If the icount is impossible, make some worst-case assumptions. */
	if (icount == NULLAGINO ||
	    !xfs_verify_agino(mp, sm->sm_agno, icount)) {
		xfs_agino_t	first, last;

		xfs_agino_range(mp, sm->sm_agno, &first, &last);
		icount = last - first + 1;
	}

	/* If the block counts are impossible, make worst-case assumptions. */
	if (aglen == NULLAGBLOCK ||
	    aglen != xfs_ag_block_count(mp, sm->sm_agno) ||
	    freelen >= aglen) {
		aglen = xfs_ag_block_count(mp, sm->sm_agno);
		freelen = aglen;
		usedlen = aglen;
	}

	trace_xrep_calc_ag_resblks(mp, sm->sm_agno, icount, aglen,
			freelen, usedlen);

	/*
	 * Figure out how many blocks we'd need worst case to rebuild
	 * each type of btree.  Note that we can only rebuild the
	 * bnobt/cntbt or inobt/finobt as pairs.
	 */
	bnobt_sz = 2 * xfs_allocbt_calc_size(mp, freelen);
	if (xfs_sb_version_hassparseinodes(&mp->m_sb))
		inobt_sz = xfs_iallocbt_calc_size(mp, icount /
				XFS_INODES_PER_HOLEMASK_BIT);
	else
		inobt_sz = xfs_iallocbt_calc_size(mp, icount /
				XFS_INODES_PER_CHUNK);
	if (xfs_sb_version_hasfinobt(&mp->m_sb))
		inobt_sz *= 2;
	if (xfs_sb_version_hasreflink(&mp->m_sb))
		refcbt_sz = xfs_refcountbt_calc_size(mp, usedlen);
	else
		refcbt_sz = 0;
	if (xfs_sb_version_hasrmapbt(&mp->m_sb)) {
		/*
		 * Guess how many blocks we need to rebuild the rmapbt.
		 * For non-reflink filesystems we can't have more records than
		 * used blocks.  However, with reflink it's possible to have
		 * more than one rmap record per AG block.  We don't know how
		 * many rmaps there could be in the AG, so we start off with
		 * what we hope is an generous over-estimation.
		 */
		if (xfs_sb_version_hasreflink(&mp->m_sb))
			rmapbt_sz = xfs_rmapbt_calc_size(mp,
					(unsigned long long)aglen * 2);
		else
			rmapbt_sz = xfs_rmapbt_calc_size(mp, usedlen);
	} else {
		rmapbt_sz = 0;
	}

	trace_xrep_calc_ag_resblks_btsize(mp, sm->sm_agno, bnobt_sz,
			inobt_sz, rmapbt_sz, refcbt_sz);

	return max(max(bnobt_sz, inobt_sz), max(rmapbt_sz, refcbt_sz));
}

/* Allocate a block in an AG. */
int
xrep_alloc_ag_block(
	struct xfs_scrub		*sc,
	const struct xfs_owner_info	*oinfo,
	xfs_fsblock_t			*fsbno,
	enum xfs_ag_resv_type		resv)
{
	struct xfs_alloc_arg		args = {0};
	xfs_agblock_t			bno;
	int				error;

	switch (resv) {
	case XFS_AG_RESV_AGFL:
	case XFS_AG_RESV_RMAPBT:
		error = xfs_alloc_get_freelist(sc->tp, sc->sa.agf_bp, &bno, 1);
		if (error)
			return error;
		if (bno == NULLAGBLOCK)
			return -ENOSPC;
		xfs_extent_busy_reuse(sc->mp, sc->sa.agno, bno,
				1, false);
		*fsbno = XFS_AGB_TO_FSB(sc->mp, sc->sa.agno, bno);
		if (resv == XFS_AG_RESV_RMAPBT)
			xfs_ag_resv_rmapbt_alloc(sc->mp, sc->sa.agno);
		return 0;
	default:
		break;
	}

	args.tp = sc->tp;
	args.mp = sc->mp;
	args.oinfo = *oinfo;
	args.fsbno = XFS_AGB_TO_FSB(args.mp, sc->sa.agno, 0);
	args.minlen = 1;
	args.maxlen = 1;
	args.prod = 1;
	args.type = XFS_ALLOCTYPE_THIS_AG;
	args.resv = resv;

	error = xfs_alloc_vextent(&args);
	if (error)
		return error;
	if (args.fsbno == NULLFSBLOCK)
		return -ENOSPC;
	ASSERT(args.len == 1);
	*fsbno = args.fsbno;

	return 0;
}

/* Initialize a new AG btree root block with zero entries. */
int
xrep_init_btblock(
	struct xfs_scrub		*sc,
	xfs_fsblock_t			fsb,
	struct xfs_buf			**bpp,
	xfs_btnum_t			btnum,
	const struct xfs_buf_ops	*ops)
{
	struct xfs_trans		*tp = sc->tp;
	struct xfs_mount		*mp = sc->mp;
	struct xfs_buf			*bp;

	trace_xrep_init_btblock(mp, XFS_FSB_TO_AGNO(mp, fsb),
			XFS_FSB_TO_AGBNO(mp, fsb), btnum);

	ASSERT(XFS_FSB_TO_AGNO(mp, fsb) == sc->sa.agno);
	bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, XFS_FSB_TO_DADDR(mp, fsb),
			XFS_FSB_TO_BB(mp, 1), 0);
	xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
	xfs_btree_init_block(mp, bp, btnum, 0, 0, sc->sa.agno);
	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_BTREE_BUF);
	xfs_trans_log_buf(tp, bp, 0, BBTOB(bp->b_length) - 1);
	bp->b_ops = ops;
	*bpp = bp;

	return 0;
}

/*
 * Reconstructing per-AG Btrees
 *
 * When a space btree is corrupt, we don't bother trying to fix it.  Instead,
 * we scan secondary space metadata to derive the records that should be in
 * the damaged btree, initialize a fresh btree root, and insert the records.
 * Note that for rebuilding the rmapbt we scan all the primary data to
 * generate the new records.
 *
 * However, that leaves the matter of removing all the metadata describing the
 * old broken structure.  For primary metadata we use the rmap data to collect
 * every extent with a matching rmap owner (bitmap); we then iterate all other
 * metadata structures with the same rmap owner to collect the extents that
 * cannot be removed (sublist).  We then subtract sublist from bitmap to
 * derive the blocks that were used by the old btree.  These blocks can be
 * reaped.
 *
 * For rmapbt reconstructions we must use different tactics for extent
 * collection.  First we iterate all primary metadata (this excludes the old
 * rmapbt, obviously) to generate new rmap records.  The gaps in the rmap
 * records are collected as bitmap.  The bnobt records are collected as
 * sublist.  As with the other btrees we subtract sublist from bitmap, and the
 * result (since the rmapbt lives in the free space) are the blocks from the
 * old rmapbt.
 *
 * Disposal of Blocks from Old per-AG Btrees
 *
 * Now that we've constructed a new btree to replace the damaged one, we want
 * to dispose of the blocks that (we think) the old btree was using.
 * Previously, we used the rmapbt to collect the extents (bitmap) with the
 * rmap owner corresponding to the tree we rebuilt, collected extents for any
 * blocks with the same rmap owner that are owned by another data structure
 * (sublist), and subtracted sublist from bitmap.  In theory the extents
 * remaining in bitmap are the old btree's blocks.
 *
 * Unfortunately, it's possible that the btree was crosslinked with other
 * blocks on disk.  The rmap data can tell us if there are multiple owners, so
 * if the rmapbt says there is an owner of this block other than @oinfo, then
 * the block is crosslinked.  Remove the reverse mapping and continue.
 *
 * If there is one rmap record, we can free the block, which removes the
 * reverse mapping but doesn't add the block to the free space.  Our repair
 * strategy is to hope the other metadata objects crosslinked on this block
 * will be rebuilt (atop different blocks), thereby removing all the cross
 * links.
 *
 * If there are no rmap records at all, we also free the block.  If the btree
 * being rebuilt lives in the free space (bnobt/cntbt/rmapbt) then there isn't
 * supposed to be a rmap record and everything is ok.  For other btrees there
 * had to have been an rmap entry for the block to have ended up on @bitmap,
 * so if it's gone now there's something wrong and the fs will shut down.
 *
 * Note: If there are multiple rmap records with only the same rmap owner as
 * the btree we're trying to rebuild and the block is indeed owned by another
 * data structure with the same rmap owner, then the block will be in sublist
 * and therefore doesn't need disposal.  If there are multiple rmap records
 * with only the same rmap owner but the block is not owned by something with
 * the same rmap owner, the block will be freed.
 *
 * The caller is responsible for locking the AG headers for the entire rebuild
 * operation so that nothing else can sneak in and change the AG state while
 * we're not looking.  We also assume that the caller already invalidated any
 * buffers associated with @bitmap.
 */

/*
 * Invalidate buffers for per-AG btree blocks we're dumping.  This function
 * is not intended for use with file data repairs; we have bunmapi for that.
 */
int
xrep_invalidate_blocks(
	struct xfs_scrub	*sc,
	struct xfs_bitmap	*bitmap)
{
	struct xfs_bitmap_range	*bmr;
	struct xfs_bitmap_range	*n;
	struct xfs_buf		*bp;
	xfs_fsblock_t		fsbno;

	/*
	 * For each block in each extent, see if there's an incore buffer for
	 * exactly that block; if so, invalidate it.  The buffer cache only
	 * lets us look for one buffer at a time, so we have to look one block
	 * at a time.  Avoid invalidating AG headers and post-EOFS blocks
	 * because we never own those; and if we can't TRYLOCK the buffer we
	 * assume it's owned by someone else.
	 */
	for_each_xfs_bitmap_block(fsbno, bmr, n, bitmap) {
		/* Skip AG headers and post-EOFS blocks */
		if (!xfs_verify_fsbno(sc->mp, fsbno))
			continue;
		bp = xfs_buf_incore(sc->mp->m_ddev_targp,
				XFS_FSB_TO_DADDR(sc->mp, fsbno),
				XFS_FSB_TO_BB(sc->mp, 1), XBF_TRYLOCK);
		if (bp) {
			xfs_trans_bjoin(sc->tp, bp);
			xfs_trans_binval(sc->tp, bp);
		}
	}

	return 0;
}

/* Ensure the freelist is the correct size. */
int
xrep_fix_freelist(
	struct xfs_scrub	*sc,
	bool			can_shrink)
{
	struct xfs_alloc_arg	args = {0};

	args.mp = sc->mp;
	args.tp = sc->tp;
	args.agno = sc->sa.agno;
	args.alignment = 1;
	args.pag = sc->sa.pag;

	return xfs_alloc_fix_freelist(&args,
			can_shrink ? 0 : XFS_ALLOC_FLAG_NOSHRINK);
}

/*
 * Put a block back on the AGFL.
 */
STATIC int
xrep_put_freelist(
	struct xfs_scrub	*sc,
	xfs_agblock_t		agbno)
{
	int			error;

	/* Make sure there's space on the freelist. */
	error = xrep_fix_freelist(sc, true);
	if (error)
		return error;

	/*
	 * Since we're "freeing" a lost block onto the AGFL, we have to
	 * create an rmap for the block prior to merging it or else other
	 * parts will break.
	 */
	error = xfs_rmap_alloc(sc->tp, sc->sa.agf_bp, sc->sa.agno, agbno, 1,
			&XFS_RMAP_OINFO_AG);
	if (error)
		return error;

	/* Put the block on the AGFL. */
	error = xfs_alloc_put_freelist(sc->tp, sc->sa.agf_bp, sc->sa.agfl_bp,
			agbno, 0);
	if (error)
		return error;
	xfs_extent_busy_insert(sc->tp, sc->sa.agno, agbno, 1,
			XFS_EXTENT_BUSY_SKIP_DISCARD);

	return 0;
}

/* Dispose of a single block. */
STATIC int
xrep_reap_block(
	struct xfs_scrub		*sc,
	xfs_fsblock_t			fsbno,
	const struct xfs_owner_info	*oinfo,
	enum xfs_ag_resv_type		resv)
{
	struct xfs_btree_cur		*cur;
	struct xfs_buf			*agf_bp = NULL;
	xfs_agnumber_t			agno;
	xfs_agblock_t			agbno;
	bool				has_other_rmap;
	int				error;

	agno = XFS_FSB_TO_AGNO(sc->mp, fsbno);
	agbno = XFS_FSB_TO_AGBNO(sc->mp, fsbno);

	/*
	 * If we are repairing per-inode metadata, we need to read in the AGF
	 * buffer.  Otherwise, we're repairing a per-AG structure, so reuse
	 * the AGF buffer that the setup functions already grabbed.
	 */
	if (sc->ip) {
		error = xfs_alloc_read_agf(sc->mp, sc->tp, agno, 0, &agf_bp);
		if (error)
			return error;
		if (!agf_bp)
			return -ENOMEM;
	} else {
		agf_bp = sc->sa.agf_bp;
	}
	cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, agf_bp, agno);

	/* Can we find any other rmappings? */
	error = xfs_rmap_has_other_keys(cur, agbno, 1, oinfo, &has_other_rmap);
	xfs_btree_del_cursor(cur, error);
	if (error)
		goto out_free;

	/*
	 * If there are other rmappings, this block is cross linked and must
	 * not be freed.  Remove the reverse mapping and move on.  Otherwise,
	 * we were the only owner of the block, so free the extent, which will
	 * also remove the rmap.
	 *
	 * XXX: XFS doesn't support detecting the case where a single block
	 * metadata structure is crosslinked with a multi-block structure
	 * because the buffer cache doesn't detect aliasing problems, so we
	 * can't fix 100% of crosslinking problems (yet).  The verifiers will
	 * blow on writeout, the filesystem will shut down, and the admin gets
	 * to run xfs_repair.
	 */
	if (has_other_rmap)
		error = xfs_rmap_free(sc->tp, agf_bp, agno, agbno, 1, oinfo);
	else if (resv == XFS_AG_RESV_AGFL)
		error = xrep_put_freelist(sc, agbno);
	else
		error = xfs_free_extent(sc->tp, fsbno, 1, oinfo, resv);
	if (agf_bp != sc->sa.agf_bp)
		xfs_trans_brelse(sc->tp, agf_bp);
	if (error)
		return error;

	if (sc->ip)
		return xfs_trans_roll_inode(&sc->tp, sc->ip);
	return xrep_roll_ag_trans(sc);

out_free:
	if (agf_bp != sc->sa.agf_bp)
		xfs_trans_brelse(sc->tp, agf_bp);
	return error;
}

/* Dispose of every block of every extent in the bitmap. */
int
xrep_reap_extents(
	struct xfs_scrub		*sc,
	struct xfs_bitmap		*bitmap,
	const struct xfs_owner_info	*oinfo,
	enum xfs_ag_resv_type		type)
{
	struct xfs_bitmap_range		*bmr;
	struct xfs_bitmap_range		*n;
	xfs_fsblock_t			fsbno;
	int				error = 0;

	ASSERT(xfs_sb_version_hasrmapbt(&sc->mp->m_sb));

	for_each_xfs_bitmap_block(fsbno, bmr, n, bitmap) {
		ASSERT(sc->ip != NULL ||
		       XFS_FSB_TO_AGNO(sc->mp, fsbno) == sc->sa.agno);
		trace_xrep_dispose_btree_extent(sc->mp,
				XFS_FSB_TO_AGNO(sc->mp, fsbno),
				XFS_FSB_TO_AGBNO(sc->mp, fsbno), 1);

		error = xrep_reap_block(sc, fsbno, oinfo, type);
		if (error)
			goto out;
	}

out:
	xfs_bitmap_destroy(bitmap);
	return error;
}

/*
 * Finding per-AG Btree Roots for AGF/AGI Reconstruction
 *
 * If the AGF or AGI become slightly corrupted, it may be necessary to rebuild
 * the AG headers by using the rmap data to rummage through the AG looking for
 * btree roots.  This is not guaranteed to work if the AG is heavily damaged
 * or the rmap data are corrupt.
 *
 * Callers of xrep_find_ag_btree_roots must lock the AGF and AGFL
 * buffers if the AGF is being rebuilt; or the AGF and AGI buffers if the
 * AGI is being rebuilt.  It must maintain these locks until it's safe for
 * other threads to change the btrees' shapes.  The caller provides
 * information about the btrees to look for by passing in an array of
 * xrep_find_ag_btree with the (rmap owner, buf_ops, magic) fields set.
 * The (root, height) fields will be set on return if anything is found.  The
 * last element of the array should have a NULL buf_ops to mark the end of the
 * array.
 *
 * For every rmapbt record matching any of the rmap owners in btree_info,
 * read each block referenced by the rmap record.  If the block is a btree
 * block from this filesystem matching any of the magic numbers and has a
 * level higher than what we've already seen, remember the block and the
 * height of the tree required to have such a block.  When the call completes,
 * we return the highest block we've found for each btree description; those
 * should be the roots.
 */

struct xrep_findroot {
	struct xfs_scrub		*sc;
	struct xfs_buf			*agfl_bp;
	struct xfs_agf			*agf;
	struct xrep_find_ag_btree	*btree_info;
};

/* See if our block is in the AGFL. */
STATIC int
xrep_findroot_agfl_walk(
	struct xfs_mount	*mp,
	xfs_agblock_t		bno,
	void			*priv)
{
	xfs_agblock_t		*agbno = priv;

	return (*agbno == bno) ? -ECANCELED : 0;
}

/* Does this block match the btree information passed in? */
STATIC int
xrep_findroot_block(
	struct xrep_findroot		*ri,
	struct xrep_find_ag_btree	*fab,
	uint64_t			owner,
	xfs_agblock_t			agbno,
	bool				*done_with_block)
{
	struct xfs_mount		*mp = ri->sc->mp;
	struct xfs_buf			*bp;
	struct xfs_btree_block		*btblock;
	xfs_daddr_t			daddr;
	int				block_level;
	int				error = 0;

	daddr = XFS_AGB_TO_DADDR(mp, ri->sc->sa.agno, agbno);

	/*
	 * Blocks in the AGFL have stale contents that might just happen to
	 * have a matching magic and uuid.  We don't want to pull these blocks
	 * in as part of a tree root, so we have to filter out the AGFL stuff
	 * here.  If the AGFL looks insane we'll just refuse to repair.
	 */
	if (owner == XFS_RMAP_OWN_AG) {
		error = xfs_agfl_walk(mp, ri->agf, ri->agfl_bp,
				xrep_findroot_agfl_walk, &agbno);
		if (error == -ECANCELED)
			return 0;
		if (error)
			return error;
	}

	/*
	 * Read the buffer into memory so that we can see if it's a match for
	 * our btree type.  We have no clue if it is beforehand, and we want to
	 * avoid xfs_trans_read_buf's behavior of dumping the DONE state (which
	 * will cause needless disk reads in subsequent calls to this function)
	 * and logging metadata verifier failures.
	 *
	 * Therefore, pass in NULL buffer ops.  If the buffer was already in
	 * memory from some other caller it will already have b_ops assigned.
	 * If it was in memory from a previous unsuccessful findroot_block
	 * call, the buffer won't have b_ops but it should be clean and ready
	 * for us to try to verify if the read call succeeds.  The same applies
	 * if the buffer wasn't in memory at all.
	 *
	 * Note: If we never match a btree type with this buffer, it will be
	 * left in memory with NULL b_ops.  This shouldn't be a problem unless
	 * the buffer gets written.
	 */
	error = xfs_trans_read_buf(mp, ri->sc->tp, mp->m_ddev_targp, daddr,
			mp->m_bsize, 0, &bp, NULL);
	if (error)
		return error;

	/* Ensure the block magic matches the btree type we're looking for. */
	btblock = XFS_BUF_TO_BLOCK(bp);
	ASSERT(fab->buf_ops->magic[1] != 0);
	if (btblock->bb_magic != fab->buf_ops->magic[1])
		goto out;

	/*
	 * If the buffer already has ops applied and they're not the ones for
	 * this btree type, we know this block doesn't match the btree and we
	 * can bail out.
	 *
	 * If the buffer ops match ours, someone else has already validated
	 * the block for us, so we can move on to checking if this is a root
	 * block candidate.
	 *
	 * If the buffer does not have ops, nobody has successfully validated
	 * the contents and the buffer cannot be dirty.  If the magic, uuid,
	 * and structure match this btree type then we'll move on to checking
	 * if it's a root block candidate.  If there is no match, bail out.
	 */
	if (bp->b_ops) {
		if (bp->b_ops != fab->buf_ops)
			goto out;
	} else {
		ASSERT(!xfs_trans_buf_is_dirty(bp));
		if (!uuid_equal(&btblock->bb_u.s.bb_uuid,
				&mp->m_sb.sb_meta_uuid))
			goto out;
		/*
		 * Read verifiers can reference b_ops, so we set the pointer
		 * here.  If the verifier fails we'll reset the buffer state
		 * to what it was before we touched the buffer.
		 */
		bp->b_ops = fab->buf_ops;
		fab->buf_ops->verify_read(bp);
		if (bp->b_error) {
			bp->b_ops = NULL;
			bp->b_error = 0;
			goto out;
		}

		/*
		 * Some read verifiers will (re)set b_ops, so we must be
		 * careful not to change b_ops after running the verifier.
		 */
	}

	/*
	 * This block passes the magic/uuid and verifier tests for this btree
	 * type.  We don't need the caller to try the other tree types.
	 */
	*done_with_block = true;

	/*
	 * Compare this btree block's level to the height of the current
	 * candidate root block.
	 *
	 * If the level matches the root we found previously, throw away both
	 * blocks because there can't be two candidate roots.
	 *
	 * If level is lower in the tree than the root we found previously,
	 * ignore this block.
	 */
	block_level = xfs_btree_get_level(btblock);
	if (block_level + 1 == fab->height) {
		fab->root = NULLAGBLOCK;
		goto out;
	} else if (block_level < fab->height) {
		goto out;
	}

	/*
	 * This is the highest block in the tree that we've found so far.
	 * Update the btree height to reflect what we've learned from this
	 * block.
	 */
	fab->height = block_level + 1;

	/*
	 * If this block doesn't have sibling pointers, then it's the new root
	 * block candidate.  Otherwise, the root will be found farther up the
	 * tree.
	 */
	if (btblock->bb_u.s.bb_leftsib == cpu_to_be32(NULLAGBLOCK) &&
	    btblock->bb_u.s.bb_rightsib == cpu_to_be32(NULLAGBLOCK))
		fab->root = agbno;
	else
		fab->root = NULLAGBLOCK;

	trace_xrep_findroot_block(mp, ri->sc->sa.agno, agbno,
			be32_to_cpu(btblock->bb_magic), fab->height - 1);
out:
	xfs_trans_brelse(ri->sc->tp, bp);
	return error;
}

/*
 * Do any of the blocks in this rmap record match one of the btrees we're
 * looking for?
 */
STATIC int
xrep_findroot_rmap(
	struct xfs_btree_cur		*cur,
	struct xfs_rmap_irec		*rec,
	void				*priv)
{
	struct xrep_findroot		*ri = priv;
	struct xrep_find_ag_btree	*fab;
	xfs_agblock_t			b;
	bool				done;
	int				error = 0;

	/* Ignore anything that isn't AG metadata. */
	if (!XFS_RMAP_NON_INODE_OWNER(rec->rm_owner))
		return 0;

	/* Otherwise scan each block + btree type. */
	for (b = 0; b < rec->rm_blockcount; b++) {
		done = false;
		for (fab = ri->btree_info; fab->buf_ops; fab++) {
			if (rec->rm_owner != fab->rmap_owner)
				continue;
			error = xrep_findroot_block(ri, fab,
					rec->rm_owner, rec->rm_startblock + b,
					&done);
			if (error)
				return error;
			if (done)
				break;
		}
	}

	return 0;
}

/* Find the roots of the per-AG btrees described in btree_info. */
int
xrep_find_ag_btree_roots(
	struct xfs_scrub		*sc,
	struct xfs_buf			*agf_bp,
	struct xrep_find_ag_btree	*btree_info,
	struct xfs_buf			*agfl_bp)
{
	struct xfs_mount		*mp = sc->mp;
	struct xrep_findroot		ri;
	struct xrep_find_ag_btree	*fab;
	struct xfs_btree_cur		*cur;
	int				error;

	ASSERT(xfs_buf_islocked(agf_bp));
	ASSERT(agfl_bp == NULL || xfs_buf_islocked(agfl_bp));

	ri.sc = sc;
	ri.btree_info = btree_info;
	ri.agf = XFS_BUF_TO_AGF(agf_bp);
	ri.agfl_bp = agfl_bp;
	for (fab = btree_info; fab->buf_ops; fab++) {
		ASSERT(agfl_bp || fab->rmap_owner != XFS_RMAP_OWN_AG);
		ASSERT(XFS_RMAP_NON_INODE_OWNER(fab->rmap_owner));
		fab->root = NULLAGBLOCK;
		fab->height = 0;
	}

	cur = xfs_rmapbt_init_cursor(mp, sc->tp, agf_bp, sc->sa.agno);
	error = xfs_rmap_query_all(cur, xrep_findroot_rmap, &ri);
	xfs_btree_del_cursor(cur, error);

	return error;
}

/* Force a quotacheck the next time we mount. */
void
xrep_force_quotacheck(
	struct xfs_scrub	*sc,
	uint			dqtype)
{
	uint			flag;

	flag = xfs_quota_chkd_flag(dqtype);
	if (!(flag & sc->mp->m_qflags))
		return;

	sc->mp->m_qflags &= ~flag;
	spin_lock(&sc->mp->m_sb_lock);
	sc->mp->m_sb.sb_qflags &= ~flag;
	spin_unlock(&sc->mp->m_sb_lock);
	xfs_log_sb(sc->tp);
}

/*
 * Attach dquots to this inode, or schedule quotacheck to fix them.
 *
 * This function ensures that the appropriate dquots are attached to an inode.
 * We cannot allow the dquot code to allocate an on-disk dquot block here
 * because we're already in transaction context with the inode locked.  The
 * on-disk dquot should already exist anyway.  If the quota code signals
 * corruption or missing quota information, schedule quotacheck, which will
 * repair corruptions in the quota metadata.
 */
int
xrep_ino_dqattach(
	struct xfs_scrub	*sc)
{
	int			error;

	error = xfs_qm_dqattach_locked(sc->ip, false);
	switch (error) {
	case -EFSBADCRC:
	case -EFSCORRUPTED:
	case -ENOENT:
		xfs_err_ratelimited(sc->mp,
"inode %llu repair encountered quota error %d, quotacheck forced.",
				(unsigned long long)sc->ip->i_ino, error);
		if (XFS_IS_UQUOTA_ON(sc->mp) && !sc->ip->i_udquot)
			xrep_force_quotacheck(sc, XFS_DQ_USER);
		if (XFS_IS_GQUOTA_ON(sc->mp) && !sc->ip->i_gdquot)
			xrep_force_quotacheck(sc, XFS_DQ_GROUP);
		if (XFS_IS_PQUOTA_ON(sc->mp) && !sc->ip->i_pdquot)
			xrep_force_quotacheck(sc, XFS_DQ_PROJ);
		/* fall through */
	case -ESRCH:
		error = 0;
		break;
	default:
		break;
	}

	return error;
}