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-rw-r--r--fs/xfs/scrub/fscounters.c381
1 files changed, 381 insertions, 0 deletions
diff --git a/fs/xfs/scrub/fscounters.c b/fs/xfs/scrub/fscounters.c
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+++ b/fs/xfs/scrub/fscounters.c
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+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 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_alloc.h"
+#include "xfs_ialloc.h"
+#include "xfs_health.h"
+#include "xfs_btree.h"
+#include "xfs_ag.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+
+/*
+ * FS Summary Counters
+ * ===================
+ *
+ * The basics of filesystem summary counter checking are that we iterate the
+ * AGs counting the number of free blocks, free space btree blocks, per-AG
+ * reservations, inodes, delayed allocation reservations, and free inodes.
+ * Then we compare what we computed against the in-core counters.
+ *
+ * However, the reality is that summary counters are a tricky beast to check.
+ * While we /could/ freeze the filesystem and scramble around the AGs counting
+ * the free blocks, in practice we prefer not do that for a scan because
+ * freezing is costly. To get around this, we added a per-cpu counter of the
+ * delalloc reservations so that we can rotor around the AGs relatively
+ * quickly, and we allow the counts to be slightly off because we're not taking
+ * any locks while we do this.
+ *
+ * So the first thing we do is warm up the buffer cache in the setup routine by
+ * walking all the AGs to make sure the incore per-AG structure has been
+ * initialized. The expected value calculation then iterates the incore per-AG
+ * structures as quickly as it can. We snapshot the percpu counters before and
+ * after this operation and use the difference in counter values to guess at
+ * our tolerance for mismatch between expected and actual counter values.
+ */
+
+/*
+ * Since the expected value computation is lockless but only browses incore
+ * values, the percpu counters should be fairly close to each other. However,
+ * we'll allow ourselves to be off by at least this (arbitrary) amount.
+ */
+#define XCHK_FSCOUNT_MIN_VARIANCE (512)
+
+/*
+ * Make sure the per-AG structure has been initialized from the on-disk header
+ * contents and trust that the incore counters match the ondisk counters. (The
+ * AGF and AGI scrubbers check them, and a normal xfs_scrub run checks the
+ * summary counters after checking all AG headers). Do this from the setup
+ * function so that the inner AG aggregation loop runs as quickly as possible.
+ *
+ * This function runs during the setup phase /before/ we start checking any
+ * metadata.
+ */
+STATIC int
+xchk_fscount_warmup(
+ struct xfs_scrub *sc)
+{
+ struct xfs_mount *mp = sc->mp;
+ struct xfs_buf *agi_bp = NULL;
+ struct xfs_buf *agf_bp = NULL;
+ struct xfs_perag *pag = NULL;
+ xfs_agnumber_t agno;
+ int error = 0;
+
+ for_each_perag(mp, agno, pag) {
+ if (xchk_should_terminate(sc, &error))
+ break;
+ if (pag->pagi_init && pag->pagf_init)
+ continue;
+
+ /* Lock both AG headers. */
+ error = xfs_ialloc_read_agi(pag, sc->tp, &agi_bp);
+ if (error)
+ break;
+ error = xfs_alloc_read_agf(pag, sc->tp, 0, &agf_bp);
+ if (error)
+ break;
+
+ /*
+ * These are supposed to be initialized by the header read
+ * function.
+ */
+ if (!pag->pagi_init || !pag->pagf_init) {
+ error = -EFSCORRUPTED;
+ break;
+ }
+
+ xfs_buf_relse(agf_bp);
+ agf_bp = NULL;
+ xfs_buf_relse(agi_bp);
+ agi_bp = NULL;
+ }
+
+ if (agf_bp)
+ xfs_buf_relse(agf_bp);
+ if (agi_bp)
+ xfs_buf_relse(agi_bp);
+ if (pag)
+ xfs_perag_put(pag);
+ return error;
+}
+
+int
+xchk_setup_fscounters(
+ struct xfs_scrub *sc)
+{
+ struct xchk_fscounters *fsc;
+ int error;
+
+ sc->buf = kmem_zalloc(sizeof(struct xchk_fscounters), 0);
+ if (!sc->buf)
+ return -ENOMEM;
+ fsc = sc->buf;
+
+ xfs_icount_range(sc->mp, &fsc->icount_min, &fsc->icount_max);
+
+ /* We must get the incore counters set up before we can proceed. */
+ error = xchk_fscount_warmup(sc);
+ if (error)
+ return error;
+
+ return xchk_trans_alloc(sc, 0);
+}
+
+/* Count free space btree blocks manually for pre-lazysbcount filesystems. */
+static int
+xchk_fscount_btreeblks(
+ struct xfs_scrub *sc,
+ struct xchk_fscounters *fsc,
+ xfs_agnumber_t agno)
+{
+ xfs_extlen_t blocks;
+ int error;
+
+ error = xchk_ag_init_existing(sc, agno, &sc->sa);
+ if (error)
+ goto out_free;
+
+ error = xfs_btree_count_blocks(sc->sa.bno_cur, &blocks);
+ if (error)
+ goto out_free;
+ fsc->fdblocks += blocks - 1;
+
+ error = xfs_btree_count_blocks(sc->sa.cnt_cur, &blocks);
+ if (error)
+ goto out_free;
+ fsc->fdblocks += blocks - 1;
+
+out_free:
+ xchk_ag_free(sc, &sc->sa);
+ return error;
+}
+
+/*
+ * Calculate what the global in-core counters ought to be from the incore
+ * per-AG structure. Callers can compare this to the actual in-core counters
+ * to estimate by how much both in-core and on-disk counters need to be
+ * adjusted.
+ */
+STATIC int
+xchk_fscount_aggregate_agcounts(
+ struct xfs_scrub *sc,
+ struct xchk_fscounters *fsc)
+{
+ struct xfs_mount *mp = sc->mp;
+ struct xfs_perag *pag;
+ uint64_t delayed;
+ xfs_agnumber_t agno;
+ int tries = 8;
+ int error = 0;
+
+retry:
+ fsc->icount = 0;
+ fsc->ifree = 0;
+ fsc->fdblocks = 0;
+
+ for_each_perag(mp, agno, pag) {
+ if (xchk_should_terminate(sc, &error))
+ break;
+
+ /* This somehow got unset since the warmup? */
+ if (!pag->pagi_init || !pag->pagf_init) {
+ error = -EFSCORRUPTED;
+ break;
+ }
+
+ /* Count all the inodes */
+ fsc->icount += pag->pagi_count;
+ fsc->ifree += pag->pagi_freecount;
+
+ /* Add up the free/freelist/bnobt/cntbt blocks */
+ fsc->fdblocks += pag->pagf_freeblks;
+ fsc->fdblocks += pag->pagf_flcount;
+ if (xfs_has_lazysbcount(sc->mp)) {
+ fsc->fdblocks += pag->pagf_btreeblks;
+ } else {
+ error = xchk_fscount_btreeblks(sc, fsc, agno);
+ if (error)
+ break;
+ }
+
+ /*
+ * Per-AG reservations are taken out of the incore counters,
+ * so they must be left out of the free blocks computation.
+ */
+ fsc->fdblocks -= pag->pag_meta_resv.ar_reserved;
+ fsc->fdblocks -= pag->pag_rmapbt_resv.ar_orig_reserved;
+
+ }
+ if (pag)
+ xfs_perag_put(pag);
+ if (error)
+ return error;
+
+ /*
+ * The global incore space reservation is taken from the incore
+ * counters, so leave that out of the computation.
+ */
+ fsc->fdblocks -= mp->m_resblks_avail;
+
+ /*
+ * Delayed allocation reservations are taken out of the incore counters
+ * but not recorded on disk, so leave them and their indlen blocks out
+ * of the computation.
+ */
+ delayed = percpu_counter_sum(&mp->m_delalloc_blks);
+ fsc->fdblocks -= delayed;
+
+ trace_xchk_fscounters_calc(mp, fsc->icount, fsc->ifree, fsc->fdblocks,
+ delayed);
+
+
+ /* Bail out if the values we compute are totally nonsense. */
+ if (fsc->icount < fsc->icount_min || fsc->icount > fsc->icount_max ||
+ fsc->fdblocks > mp->m_sb.sb_dblocks ||
+ fsc->ifree > fsc->icount_max)
+ return -EFSCORRUPTED;
+
+ /*
+ * If ifree > icount then we probably had some perturbation in the
+ * counters while we were calculating things. We'll try a few times
+ * to maintain ifree <= icount before giving up.
+ */
+ if (fsc->ifree > fsc->icount) {
+ if (tries--)
+ goto retry;
+ xchk_set_incomplete(sc);
+ return 0;
+ }
+
+ return 0;
+}
+
+/*
+ * Is the @counter reasonably close to the @expected value?
+ *
+ * We neither locked nor froze anything in the filesystem while aggregating the
+ * per-AG data to compute the @expected value, which means that the counter
+ * could have changed. We know the @old_value of the summation of the counter
+ * before the aggregation, and we re-sum the counter now. If the expected
+ * value falls between the two summations, we're ok.
+ *
+ * Otherwise, we /might/ have a problem. If the change in the summations is
+ * more than we want to tolerate, the filesystem is probably busy and we should
+ * just send back INCOMPLETE and see if userspace will try again.
+ */
+static inline bool
+xchk_fscount_within_range(
+ struct xfs_scrub *sc,
+ const int64_t old_value,
+ struct percpu_counter *counter,
+ uint64_t expected)
+{
+ int64_t min_value, max_value;
+ int64_t curr_value = percpu_counter_sum(counter);
+
+ trace_xchk_fscounters_within_range(sc->mp, expected, curr_value,
+ old_value);
+
+ /* Negative values are always wrong. */
+ if (curr_value < 0)
+ return false;
+
+ /* Exact matches are always ok. */
+ if (curr_value == expected)
+ return true;
+
+ min_value = min(old_value, curr_value);
+ max_value = max(old_value, curr_value);
+
+ /* Within the before-and-after range is ok. */
+ if (expected >= min_value && expected <= max_value)
+ return true;
+
+ /*
+ * If the difference between the two summations is too large, the fs
+ * might just be busy and so we'll mark the scrub incomplete. Return
+ * true here so that we don't mark the counter corrupt.
+ *
+ * XXX: In the future when userspace can grant scrub permission to
+ * quiesce the filesystem to solve the outsized variance problem, this
+ * check should be moved up and the return code changed to signal to
+ * userspace that we need quiesce permission.
+ */
+ if (max_value - min_value >= XCHK_FSCOUNT_MIN_VARIANCE) {
+ xchk_set_incomplete(sc);
+ return true;
+ }
+
+ return false;
+}
+
+/* Check the superblock counters. */
+int
+xchk_fscounters(
+ struct xfs_scrub *sc)
+{
+ struct xfs_mount *mp = sc->mp;
+ struct xchk_fscounters *fsc = sc->buf;
+ int64_t icount, ifree, fdblocks;
+ int error;
+
+ /* Snapshot the percpu counters. */
+ icount = percpu_counter_sum(&mp->m_icount);
+ ifree = percpu_counter_sum(&mp->m_ifree);
+ fdblocks = percpu_counter_sum(&mp->m_fdblocks);
+
+ /* No negative values, please! */
+ if (icount < 0 || ifree < 0 || fdblocks < 0)
+ xchk_set_corrupt(sc);
+
+ /* See if icount is obviously wrong. */
+ if (icount < fsc->icount_min || icount > fsc->icount_max)
+ xchk_set_corrupt(sc);
+
+ /* See if fdblocks is obviously wrong. */
+ if (fdblocks > mp->m_sb.sb_dblocks)
+ xchk_set_corrupt(sc);
+
+ /*
+ * XXX: We can't quiesce percpu counter updates, so exit early.
+ * This can be re-enabled when we gain exclusive freeze functionality.
+ */
+ return 0;
+
+ /*
+ * If ifree exceeds icount by more than the minimum variance then
+ * something's probably wrong with the counters.
+ */
+ if (ifree > icount && ifree - icount > XCHK_FSCOUNT_MIN_VARIANCE)
+ xchk_set_corrupt(sc);
+
+ /* Walk the incore AG headers to calculate the expected counters. */
+ error = xchk_fscount_aggregate_agcounts(sc, fsc);
+ if (!xchk_process_error(sc, 0, XFS_SB_BLOCK(mp), &error))
+ return error;
+ if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE)
+ return 0;
+
+ /* Compare the in-core counters with whatever we counted. */
+ if (!xchk_fscount_within_range(sc, icount, &mp->m_icount, fsc->icount))
+ xchk_set_corrupt(sc);
+
+ if (!xchk_fscount_within_range(sc, ifree, &mp->m_ifree, fsc->ifree))
+ xchk_set_corrupt(sc);
+
+ if (!xchk_fscount_within_range(sc, fdblocks, &mp->m_fdblocks,
+ fsc->fdblocks))
+ xchk_set_corrupt(sc);
+
+ return 0;
+}