1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright (C) 2019-2023 Oracle. All Rights Reserved.
8 #include "xfs_shared.h"
9 #include "xfs_format.h"
10 #include "xfs_trans_resv.h"
11 #include "xfs_log_format.h"
12 #include "xfs_trans.h"
13 #include "xfs_mount.h"
14 #include "xfs_alloc.h"
15 #include "xfs_ialloc.h"
16 #include "xfs_health.h"
17 #include "xfs_btree.h"
19 #include "xfs_rtbitmap.h"
20 #include "xfs_inode.h"
21 #include "xfs_icache.h"
22 #include "scrub/scrub.h"
23 #include "scrub/common.h"
24 #include "scrub/trace.h"
25 #include "scrub/fscounters.h"
31 * The basics of filesystem summary counter checking are that we iterate the
32 * AGs counting the number of free blocks, free space btree blocks, per-AG
33 * reservations, inodes, delayed allocation reservations, and free inodes.
34 * Then we compare what we computed against the in-core counters.
36 * However, the reality is that summary counters are a tricky beast to check.
37 * While we /could/ freeze the filesystem and scramble around the AGs counting
38 * the free blocks, in practice we prefer not do that for a scan because
39 * freezing is costly. To get around this, we added a per-cpu counter of the
40 * delalloc reservations so that we can rotor around the AGs relatively
41 * quickly, and we allow the counts to be slightly off because we're not taking
42 * any locks while we do this.
44 * So the first thing we do is warm up the buffer cache in the setup routine by
45 * walking all the AGs to make sure the incore per-AG structure has been
46 * initialized. The expected value calculation then iterates the incore per-AG
47 * structures as quickly as it can. We snapshot the percpu counters before and
48 * after this operation and use the difference in counter values to guess at
49 * our tolerance for mismatch between expected and actual counter values.
53 * Since the expected value computation is lockless but only browses incore
54 * values, the percpu counters should be fairly close to each other. However,
55 * we'll allow ourselves to be off by at least this (arbitrary) amount.
57 #define XCHK_FSCOUNT_MIN_VARIANCE (512)
60 * Make sure the per-AG structure has been initialized from the on-disk header
61 * contents and trust that the incore counters match the ondisk counters. (The
62 * AGF and AGI scrubbers check them, and a normal xfs_scrub run checks the
63 * summary counters after checking all AG headers). Do this from the setup
64 * function so that the inner AG aggregation loop runs as quickly as possible.
66 * This function runs during the setup phase /before/ we start checking any
73 struct xfs_mount *mp = sc->mp;
74 struct xfs_buf *agi_bp = NULL;
75 struct xfs_buf *agf_bp = NULL;
76 struct xfs_perag *pag = NULL;
80 for_each_perag(mp, agno, pag) {
81 if (xchk_should_terminate(sc, &error))
83 if (xfs_perag_initialised_agi(pag) &&
84 xfs_perag_initialised_agf(pag))
87 /* Lock both AG headers. */
88 error = xfs_ialloc_read_agi(pag, sc->tp, 0, &agi_bp);
91 error = xfs_alloc_read_agf(pag, sc->tp, 0, &agf_bp);
96 * These are supposed to be initialized by the header read
99 if (!xfs_perag_initialised_agi(pag) ||
100 !xfs_perag_initialised_agf(pag)) {
101 error = -EFSCORRUPTED;
105 xfs_buf_relse(agf_bp);
107 xfs_buf_relse(agi_bp);
112 xfs_buf_relse(agf_bp);
114 xfs_buf_relse(agi_bp);
122 struct xfs_scrub *sc)
126 error = freeze_super(sc->mp->m_super, FREEZE_HOLDER_KERNEL);
127 trace_xchk_fsfreeze(sc, error);
133 struct xfs_scrub *sc)
137 /* This should always succeed, we have a kernel freeze */
138 error = thaw_super(sc->mp->m_super, FREEZE_HOLDER_KERNEL);
139 trace_xchk_fsthaw(sc, error);
144 * We couldn't stabilize the filesystem long enough to sample all the variables
145 * that comprise the summary counters and compare them to the percpu counters.
146 * We need to disable all writer threads, which means taking the first two
147 * freeze levels to put userspace to sleep, and the third freeze level to
148 * prevent background threads from starting new transactions. Take one level
149 * more to prevent other callers from unfreezing the filesystem while we run.
152 xchk_fscounters_freeze(
153 struct xfs_scrub *sc)
155 struct xchk_fscounters *fsc = sc->buf;
158 if (sc->flags & XCHK_HAVE_FREEZE_PROT) {
159 sc->flags &= ~XCHK_HAVE_FREEZE_PROT;
160 mnt_drop_write_file(sc->file);
163 /* Try to grab a kernel freeze. */
164 while ((error = xchk_fsfreeze(sc)) == -EBUSY) {
165 if (xchk_should_terminate(sc, &error))
177 /* Thaw the filesystem after checking or repairing fscounters. */
179 xchk_fscounters_cleanup(
182 struct xchk_fscounters *fsc = buf;
183 struct xfs_scrub *sc = fsc->sc;
189 error = xchk_fsthaw(sc);
191 xfs_emerg(sc->mp, "still frozen after scrub, err=%d", error);
197 xchk_setup_fscounters(
198 struct xfs_scrub *sc)
200 struct xchk_fscounters *fsc;
204 * If the AGF doesn't track btreeblks, we have to lock the AGF to count
205 * btree block usage by walking the actual btrees.
207 if (!xfs_has_lazysbcount(sc->mp))
208 xchk_fsgates_enable(sc, XCHK_FSGATES_DRAIN);
210 sc->buf = kzalloc(sizeof(struct xchk_fscounters), XCHK_GFP_FLAGS);
213 sc->buf_cleanup = xchk_fscounters_cleanup;
217 xfs_icount_range(sc->mp, &fsc->icount_min, &fsc->icount_max);
219 /* We must get the incore counters set up before we can proceed. */
220 error = xchk_fscount_warmup(sc);
225 * Pause all writer activity in the filesystem while we're scrubbing to
226 * reduce the likelihood of background perturbations to the counters
227 * throwing off our calculations.
229 * If we're repairing, we need to prevent any other thread from
230 * changing the global fs summary counters while we're repairing them.
231 * This requires the fs to be frozen, which will disable background
232 * reclaim and purge all inactive inodes.
234 if ((sc->flags & XCHK_TRY_HARDER) || xchk_could_repair(sc)) {
235 error = xchk_fscounters_freeze(sc);
240 return xchk_trans_alloc_empty(sc);
244 * Part 1: Collecting filesystem summary counts. For each AG, we add its
245 * summary counts (total inodes, free inodes, free data blocks) to an incore
246 * copy of the overall filesystem summary counts.
248 * To avoid false corruption reports in part 2, any failure in this part must
249 * set the INCOMPLETE flag even when a negative errno is returned. This care
250 * must be taken with certain errno values (i.e. EFSBADCRC, EFSCORRUPTED,
251 * ECANCELED) that are absorbed into a scrub state flag update by
252 * xchk_*_process_error. Scrub and repair share the same incore data
253 * structures, so the INCOMPLETE flag is critical to prevent a repair based on
254 * insufficient information.
257 /* Count free space btree blocks manually for pre-lazysbcount filesystems. */
259 xchk_fscount_btreeblks(
260 struct xfs_scrub *sc,
261 struct xchk_fscounters *fsc,
267 error = xchk_ag_init_existing(sc, agno, &sc->sa);
271 error = xfs_btree_count_blocks(sc->sa.bno_cur, &blocks);
274 fsc->fdblocks += blocks - 1;
276 error = xfs_btree_count_blocks(sc->sa.cnt_cur, &blocks);
279 fsc->fdblocks += blocks - 1;
282 xchk_ag_free(sc, &sc->sa);
287 * Calculate what the global in-core counters ought to be from the incore
288 * per-AG structure. Callers can compare this to the actual in-core counters
289 * to estimate by how much both in-core and on-disk counters need to be
293 xchk_fscount_aggregate_agcounts(
294 struct xfs_scrub *sc,
295 struct xchk_fscounters *fsc)
297 struct xfs_mount *mp = sc->mp;
298 struct xfs_perag *pag;
309 for_each_perag(mp, agno, pag) {
310 if (xchk_should_terminate(sc, &error))
313 /* This somehow got unset since the warmup? */
314 if (!xfs_perag_initialised_agi(pag) ||
315 !xfs_perag_initialised_agf(pag)) {
316 error = -EFSCORRUPTED;
320 /* Count all the inodes */
321 fsc->icount += pag->pagi_count;
322 fsc->ifree += pag->pagi_freecount;
324 /* Add up the free/freelist/bnobt/cntbt blocks */
325 fsc->fdblocks += pag->pagf_freeblks;
326 fsc->fdblocks += pag->pagf_flcount;
327 if (xfs_has_lazysbcount(sc->mp)) {
328 fsc->fdblocks += pag->pagf_btreeblks;
330 error = xchk_fscount_btreeblks(sc, fsc, agno);
336 * Per-AG reservations are taken out of the incore counters,
337 * so they must be left out of the free blocks computation.
339 fsc->fdblocks -= pag->pag_meta_resv.ar_reserved;
340 fsc->fdblocks -= pag->pag_rmapbt_resv.ar_orig_reserved;
346 xchk_set_incomplete(sc);
351 * The global incore space reservation is taken from the incore
352 * counters, so leave that out of the computation.
354 fsc->fdblocks -= mp->m_resblks_avail;
357 * Delayed allocation reservations are taken out of the incore counters
358 * but not recorded on disk, so leave them and their indlen blocks out
359 * of the computation.
361 delayed = percpu_counter_sum(&mp->m_delalloc_blks);
362 fsc->fdblocks -= delayed;
364 trace_xchk_fscounters_calc(mp, fsc->icount, fsc->ifree, fsc->fdblocks,
368 /* Bail out if the values we compute are totally nonsense. */
369 if (fsc->icount < fsc->icount_min || fsc->icount > fsc->icount_max ||
370 fsc->fdblocks > mp->m_sb.sb_dblocks ||
371 fsc->ifree > fsc->icount_max)
372 return -EFSCORRUPTED;
375 * If ifree > icount then we probably had some perturbation in the
376 * counters while we were calculating things. We'll try a few times
377 * to maintain ifree <= icount before giving up.
379 if (fsc->ifree > fsc->icount) {
390 xchk_fscount_add_frextent(
391 struct xfs_mount *mp,
392 struct xfs_trans *tp,
393 const struct xfs_rtalloc_rec *rec,
396 struct xchk_fscounters *fsc = priv;
399 fsc->frextents += rec->ar_extcount;
401 xchk_should_terminate(fsc->sc, &error);
405 /* Calculate the number of free realtime extents from the realtime bitmap. */
407 xchk_fscount_count_frextents(
408 struct xfs_scrub *sc,
409 struct xchk_fscounters *fsc)
411 struct xfs_mount *mp = sc->mp;
415 fsc->frextents_delayed = 0;
416 if (!xfs_has_realtime(mp))
419 xfs_rtbitmap_lock_shared(sc->mp, XFS_RBMLOCK_BITMAP);
420 error = xfs_rtalloc_query_all(sc->mp, sc->tp,
421 xchk_fscount_add_frextent, fsc);
423 xchk_set_incomplete(sc);
427 fsc->frextents_delayed = percpu_counter_sum(&mp->m_delalloc_rtextents);
430 xfs_rtbitmap_unlock_shared(sc->mp, XFS_RBMLOCK_BITMAP);
435 xchk_fscount_count_frextents(
436 struct xfs_scrub *sc,
437 struct xchk_fscounters *fsc)
440 fsc->frextents_delayed = 0;
443 #endif /* CONFIG_XFS_RT */
446 * Part 2: Comparing filesystem summary counters. All we have to do here is
447 * sum the percpu counters and compare them to what we've observed.
451 * Is the @counter reasonably close to the @expected value?
453 * We neither locked nor froze anything in the filesystem while aggregating the
454 * per-AG data to compute the @expected value, which means that the counter
455 * could have changed. We know the @old_value of the summation of the counter
456 * before the aggregation, and we re-sum the counter now. If the expected
457 * value falls between the two summations, we're ok.
459 * Otherwise, we /might/ have a problem. If the change in the summations is
460 * more than we want to tolerate, the filesystem is probably busy and we should
461 * just send back INCOMPLETE and see if userspace will try again.
463 * If we're repairing then we require an exact match.
466 xchk_fscount_within_range(
467 struct xfs_scrub *sc,
468 const int64_t old_value,
469 struct percpu_counter *counter,
472 int64_t min_value, max_value;
473 int64_t curr_value = percpu_counter_sum(counter);
475 trace_xchk_fscounters_within_range(sc->mp, expected, curr_value,
478 /* Negative values are always wrong. */
482 /* Exact matches are always ok. */
483 if (curr_value == expected)
486 /* We require exact matches when repair is running. */
487 if (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR)
490 min_value = min(old_value, curr_value);
491 max_value = max(old_value, curr_value);
493 /* Within the before-and-after range is ok. */
494 if (expected >= min_value && expected <= max_value)
497 /* Everything else is bad. */
501 /* Check the superblock counters. */
504 struct xfs_scrub *sc)
506 struct xfs_mount *mp = sc->mp;
507 struct xchk_fscounters *fsc = sc->buf;
508 int64_t icount, ifree, fdblocks, frextents;
509 bool try_again = false;
512 /* Snapshot the percpu counters. */
513 icount = percpu_counter_sum(&mp->m_icount);
514 ifree = percpu_counter_sum(&mp->m_ifree);
515 fdblocks = percpu_counter_sum(&mp->m_fdblocks);
516 frextents = percpu_counter_sum(&mp->m_frextents);
518 /* No negative values, please! */
519 if (icount < 0 || ifree < 0)
520 xchk_set_corrupt(sc);
523 * If the filesystem is not frozen, the counter summation calls above
524 * can race with xfs_dec_freecounter, which subtracts a requested space
525 * reservation from the counter and undoes the subtraction if that made
526 * the counter go negative. Therefore, it's possible to see negative
527 * values here, and we should only flag that as a corruption if we
528 * froze the fs. This is much more likely to happen with frextents
529 * since there are no reserved pools.
531 if (fdblocks < 0 || frextents < 0) {
535 xchk_set_corrupt(sc);
539 /* See if icount is obviously wrong. */
540 if (icount < fsc->icount_min || icount > fsc->icount_max)
541 xchk_set_corrupt(sc);
543 /* See if fdblocks is obviously wrong. */
544 if (fdblocks > mp->m_sb.sb_dblocks)
545 xchk_set_corrupt(sc);
547 /* See if frextents is obviously wrong. */
548 if (frextents > mp->m_sb.sb_rextents)
549 xchk_set_corrupt(sc);
552 * If ifree exceeds icount by more than the minimum variance then
553 * something's probably wrong with the counters.
555 if (ifree > icount && ifree - icount > XCHK_FSCOUNT_MIN_VARIANCE)
556 xchk_set_corrupt(sc);
558 /* Walk the incore AG headers to calculate the expected counters. */
559 error = xchk_fscount_aggregate_agcounts(sc, fsc);
560 if (!xchk_process_error(sc, 0, XFS_SB_BLOCK(mp), &error))
563 /* Count the free extents counter for rt volumes. */
564 error = xchk_fscount_count_frextents(sc, fsc);
565 if (!xchk_process_error(sc, 0, XFS_SB_BLOCK(mp), &error))
567 if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE)
571 * Compare the in-core counters with whatever we counted. If the fs is
572 * frozen, we treat the discrepancy as a corruption because the freeze
573 * should have stabilized the counter values. Otherwise, we need
574 * userspace to call us back having granted us freeze permission.
576 if (!xchk_fscount_within_range(sc, icount, &mp->m_icount,
579 xchk_set_corrupt(sc);
584 if (!xchk_fscount_within_range(sc, ifree, &mp->m_ifree, fsc->ifree)) {
586 xchk_set_corrupt(sc);
591 if (!xchk_fscount_within_range(sc, fdblocks, &mp->m_fdblocks,
594 xchk_set_corrupt(sc);
599 if (!xchk_fscount_within_range(sc, frextents, &mp->m_frextents,
600 fsc->frextents - fsc->frextents_delayed)) {
602 xchk_set_corrupt(sc);