1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (C) 2019 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
8 #include "xfs_shared.h"
9 #include "xfs_format.h"
10 #include "xfs_trans_resv.h"
11 #include "xfs_mount.h"
13 #include "xfs_alloc.h"
14 #include "xfs_ialloc.h"
15 #include "xfs_health.h"
16 #include "scrub/scrub.h"
17 #include "scrub/common.h"
18 #include "scrub/trace.h"
24 * The basics of filesystem summary counter checking are that we iterate the
25 * AGs counting the number of free blocks, free space btree blocks, per-AG
26 * reservations, inodes, delayed allocation reservations, and free inodes.
27 * Then we compare what we computed against the in-core counters.
29 * However, the reality is that summary counters are a tricky beast to check.
30 * While we /could/ freeze the filesystem and scramble around the AGs counting
31 * the free blocks, in practice we prefer not do that for a scan because
32 * freezing is costly. To get around this, we added a per-cpu counter of the
33 * delalloc reservations so that we can rotor around the AGs relatively
34 * quickly, and we allow the counts to be slightly off because we're not taking
35 * any locks while we do this.
37 * So the first thing we do is warm up the buffer cache in the setup routine by
38 * walking all the AGs to make sure the incore per-AG structure has been
39 * initialized. The expected value calculation then iterates the incore per-AG
40 * structures as quickly as it can. We snapshot the percpu counters before and
41 * after this operation and use the difference in counter values to guess at
42 * our tolerance for mismatch between expected and actual counter values.
46 * Since the expected value computation is lockless but only browses incore
47 * values, the percpu counters should be fairly close to each other. However,
48 * we'll allow ourselves to be off by at least this (arbitrary) amount.
50 #define XCHK_FSCOUNT_MIN_VARIANCE (512)
53 * Make sure the per-AG structure has been initialized from the on-disk header
54 * contents and trust that the incore counters match the ondisk counters. (The
55 * AGF and AGI scrubbers check them, and a normal xfs_scrub run checks the
56 * summary counters after checking all AG headers). Do this from the setup
57 * function so that the inner AG aggregation loop runs as quickly as possible.
59 * This function runs during the setup phase /before/ we start checking any
66 struct xfs_mount *mp = sc->mp;
67 struct xfs_buf *agi_bp = NULL;
68 struct xfs_buf *agf_bp = NULL;
69 struct xfs_perag *pag = NULL;
73 for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
74 pag = xfs_perag_get(mp, agno);
76 if (pag->pagi_init && pag->pagf_init)
79 /* Lock both AG headers. */
80 error = xfs_ialloc_read_agi(mp, sc->tp, agno, &agi_bp);
83 error = xfs_alloc_read_agf(mp, sc->tp, agno, 0, &agf_bp);
87 if (!agf_bp || !agi_bp)
91 * These are supposed to be initialized by the header read
94 error = -EFSCORRUPTED;
95 if (!pag->pagi_init || !pag->pagf_init)
98 xfs_buf_relse(agf_bp);
100 xfs_buf_relse(agi_bp);
107 if (xchk_should_terminate(sc, &error))
112 xfs_buf_relse(agf_bp);
114 xfs_buf_relse(agi_bp);
121 xchk_setup_fscounters(
122 struct xfs_scrub *sc,
123 struct xfs_inode *ip)
125 struct xchk_fscounters *fsc;
128 sc->buf = kmem_zalloc(sizeof(struct xchk_fscounters), 0);
133 xfs_icount_range(sc->mp, &fsc->icount_min, &fsc->icount_max);
135 /* We must get the incore counters set up before we can proceed. */
136 error = xchk_fscount_warmup(sc);
141 * Pause background reclaim while we're scrubbing to reduce the
142 * likelihood of background perturbations to the counters throwing off
145 xchk_stop_reaping(sc);
147 return xchk_trans_alloc(sc, 0);
151 * Calculate what the global in-core counters ought to be from the incore
152 * per-AG structure. Callers can compare this to the actual in-core counters
153 * to estimate by how much both in-core and on-disk counters need to be
157 xchk_fscount_aggregate_agcounts(
158 struct xfs_scrub *sc,
159 struct xchk_fscounters *fsc)
161 struct xfs_mount *mp = sc->mp;
162 struct xfs_perag *pag;
173 for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
174 pag = xfs_perag_get(mp, agno);
176 /* This somehow got unset since the warmup? */
177 if (!pag->pagi_init || !pag->pagf_init) {
179 return -EFSCORRUPTED;
182 /* Count all the inodes */
183 fsc->icount += pag->pagi_count;
184 fsc->ifree += pag->pagi_freecount;
186 /* Add up the free/freelist/bnobt/cntbt blocks */
187 fsc->fdblocks += pag->pagf_freeblks;
188 fsc->fdblocks += pag->pagf_flcount;
189 fsc->fdblocks += pag->pagf_btreeblks;
192 * Per-AG reservations are taken out of the incore counters,
193 * so they must be left out of the free blocks computation.
195 fsc->fdblocks -= pag->pag_meta_resv.ar_reserved;
196 fsc->fdblocks -= pag->pag_rmapbt_resv.ar_orig_reserved;
200 if (xchk_should_terminate(sc, &error))
208 * The global incore space reservation is taken from the incore
209 * counters, so leave that out of the computation.
211 fsc->fdblocks -= mp->m_resblks_avail;
214 * Delayed allocation reservations are taken out of the incore counters
215 * but not recorded on disk, so leave them and their indlen blocks out
216 * of the computation.
218 delayed = percpu_counter_sum(&mp->m_delalloc_blks);
219 fsc->fdblocks -= delayed;
221 trace_xchk_fscounters_calc(mp, fsc->icount, fsc->ifree, fsc->fdblocks,
225 /* Bail out if the values we compute are totally nonsense. */
226 if (fsc->icount < fsc->icount_min || fsc->icount > fsc->icount_max ||
227 fsc->fdblocks > mp->m_sb.sb_dblocks ||
228 fsc->ifree > fsc->icount_max)
229 return -EFSCORRUPTED;
232 * If ifree > icount then we probably had some perturbation in the
233 * counters while we were calculating things. We'll try a few times
234 * to maintain ifree <= icount before giving up.
236 if (fsc->ifree > fsc->icount) {
239 xchk_set_incomplete(sc);
247 * Is the @counter reasonably close to the @expected value?
249 * We neither locked nor froze anything in the filesystem while aggregating the
250 * per-AG data to compute the @expected value, which means that the counter
251 * could have changed. We know the @old_value of the summation of the counter
252 * before the aggregation, and we re-sum the counter now. If the expected
253 * value falls between the two summations, we're ok.
255 * Otherwise, we /might/ have a problem. If the change in the summations is
256 * more than we want to tolerate, the filesystem is probably busy and we should
257 * just send back INCOMPLETE and see if userspace will try again.
260 xchk_fscount_within_range(
261 struct xfs_scrub *sc,
262 const int64_t old_value,
263 struct percpu_counter *counter,
266 int64_t min_value, max_value;
267 int64_t curr_value = percpu_counter_sum(counter);
269 trace_xchk_fscounters_within_range(sc->mp, expected, curr_value,
272 /* Negative values are always wrong. */
276 /* Exact matches are always ok. */
277 if (curr_value == expected)
280 min_value = min(old_value, curr_value);
281 max_value = max(old_value, curr_value);
283 /* Within the before-and-after range is ok. */
284 if (expected >= min_value && expected <= max_value)
288 * If the difference between the two summations is too large, the fs
289 * might just be busy and so we'll mark the scrub incomplete. Return
290 * true here so that we don't mark the counter corrupt.
292 * XXX: In the future when userspace can grant scrub permission to
293 * quiesce the filesystem to solve the outsized variance problem, this
294 * check should be moved up and the return code changed to signal to
295 * userspace that we need quiesce permission.
297 if (max_value - min_value >= XCHK_FSCOUNT_MIN_VARIANCE) {
298 xchk_set_incomplete(sc);
305 /* Check the superblock counters. */
308 struct xfs_scrub *sc)
310 struct xfs_mount *mp = sc->mp;
311 struct xchk_fscounters *fsc = sc->buf;
312 int64_t icount, ifree, fdblocks;
315 /* Snapshot the percpu counters. */
316 icount = percpu_counter_sum(&mp->m_icount);
317 ifree = percpu_counter_sum(&mp->m_ifree);
318 fdblocks = percpu_counter_sum(&mp->m_fdblocks);
320 /* No negative values, please! */
321 if (icount < 0 || ifree < 0 || fdblocks < 0)
322 xchk_set_corrupt(sc);
324 /* See if icount is obviously wrong. */
325 if (icount < fsc->icount_min || icount > fsc->icount_max)
326 xchk_set_corrupt(sc);
328 /* See if fdblocks is obviously wrong. */
329 if (fdblocks > mp->m_sb.sb_dblocks)
330 xchk_set_corrupt(sc);
333 * If ifree exceeds icount by more than the minimum variance then
334 * something's probably wrong with the counters.
336 if (ifree > icount && ifree - icount > XCHK_FSCOUNT_MIN_VARIANCE)
337 xchk_set_corrupt(sc);
339 /* Walk the incore AG headers to calculate the expected counters. */
340 error = xchk_fscount_aggregate_agcounts(sc, fsc);
341 if (!xchk_process_error(sc, 0, XFS_SB_BLOCK(mp), &error))
343 if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE)
346 /* Compare the in-core counters with whatever we counted. */
347 if (!xchk_fscount_within_range(sc, icount, &mp->m_icount, fsc->icount))
348 xchk_set_corrupt(sc);
350 if (!xchk_fscount_within_range(sc, ifree, &mp->m_ifree, fsc->ifree))
351 xchk_set_corrupt(sc);
353 if (!xchk_fscount_within_range(sc, fdblocks, &mp->m_fdblocks,
355 xchk_set_corrupt(sc);