| // 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_sb.h" |
| #include "xfs_alloc.h" |
| #include "xfs_ialloc.h" |
| #include "xfs_health.h" |
| #include "xfs_btree.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 (agno = 0; agno < mp->m_sb.sb_agcount; agno++) { |
| pag = xfs_perag_get(mp, agno); |
| |
| if (pag->pagi_init && pag->pagf_init) |
| goto next_loop_perag; |
| |
| /* Lock both AG headers. */ |
| error = xfs_ialloc_read_agi(mp, sc->tp, agno, &agi_bp); |
| if (error) |
| break; |
| error = xfs_alloc_read_agf(mp, sc->tp, agno, 0, &agf_bp); |
| if (error) |
| break; |
| |
| /* |
| * These are supposed to be initialized by the header read |
| * function. |
| */ |
| error = -EFSCORRUPTED; |
| if (!pag->pagi_init || !pag->pagf_init) |
| break; |
| |
| xfs_buf_relse(agf_bp); |
| agf_bp = NULL; |
| xfs_buf_relse(agi_bp); |
| agi_bp = NULL; |
| next_loop_perag: |
| xfs_perag_put(pag); |
| pag = NULL; |
| error = 0; |
| |
| if (xchk_should_terminate(sc, &error)) |
| break; |
| } |
| |
| 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; |
| |
| /* |
| * Pause background reclaim while we're scrubbing to reduce the |
| * likelihood of background perturbations to the counters throwing off |
| * our calculations. |
| */ |
| xchk_stop_reaping(sc); |
| |
| 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(sc, agno, &sc->sa); |
| if (error) |
| return error; |
| |
| 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 (agno = 0; agno < mp->m_sb.sb_agcount; agno++) { |
| pag = xfs_perag_get(mp, agno); |
| |
| /* This somehow got unset since the warmup? */ |
| if (!pag->pagi_init || !pag->pagf_init) { |
| xfs_perag_put(pag); |
| return -EFSCORRUPTED; |
| } |
| |
| /* 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_sb_version_haslazysbcount(&sc->mp->m_sb)) { |
| fsc->fdblocks += pag->pagf_btreeblks; |
| } else { |
| error = xchk_fscount_btreeblks(sc, fsc, agno); |
| if (error) { |
| xfs_perag_put(pag); |
| 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; |
| |
| xfs_perag_put(pag); |
| |
| if (xchk_should_terminate(sc, &error)) |
| break; |
| } |
| |
| 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); |
| |
| /* |
| * 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; |
| } |