On 05 Aug 2021 at 00:01, "Darrick J. Wong" <djwong@xxxxxxxxxx> wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> This patch prepares scrub to deal with the possibility of tearing down
> entire AGs by changing the order of resource acquisition to match the
> rest of the XFS codebase. In other words, scrub now grabs AG resources
> in order of: perag structure, then AGI/AGF/AGFL buffers, then btree
> cursors; and releases them in reverse order.
>
> This requires us to distinguish xchk_ag_init callers -- some are
> responding to a user request to check AG metadata, in which case we can
> return ENOENT to userspace; but other callers have an ondisk reference
> to an AG that they're trying to cross-reference. In this second case,
> the lack of an AG means there's ondisk corruption, since ondisk metadata
> cannot point into nonexistent space.
>
As mentioned above, with this patch applied, scrub code either obtains a
reference to a metadata belonging to an AG or obtain a reference to the pag
structure during setup phase. Also, a reference to the pag structure is
obtained before getting a reference to AGI, AGF and AGFL. Hence,
Reviewed-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> ---
> fs/xfs/scrub/agheader.c | 23 +++++++++++++------
> fs/xfs/scrub/agheader_repair.c | 3 ---
> fs/xfs/scrub/bmap.c | 2 +-
> fs/xfs/scrub/btree.c | 2 +-
> fs/xfs/scrub/common.c | 48 ++++++++++++++++------------------------
> fs/xfs/scrub/common.h | 18 ++++++++++++++-
> fs/xfs/scrub/fscounters.c | 2 +-
> fs/xfs/scrub/inode.c | 2 +-
> 8 files changed, 56 insertions(+), 44 deletions(-)
>
>
> diff --git a/fs/xfs/scrub/agheader.c b/fs/xfs/scrub/agheader.c
> index be1a7e1e65f7..6152ce01c057 100644
> --- a/fs/xfs/scrub/agheader.c
> +++ b/fs/xfs/scrub/agheader.c
> @@ -36,7 +36,7 @@ xchk_superblock_xref(
>
> agbno = XFS_SB_BLOCK(mp);
>
> - error = xchk_ag_init(sc, agno, &sc->sa);
> + error = xchk_ag_init_existing(sc, agno, &sc->sa);
> if (!xchk_xref_process_error(sc, agno, agbno, &error))
> return;
>
> @@ -63,6 +63,7 @@ xchk_superblock(
> struct xfs_mount *mp = sc->mp;
> struct xfs_buf *bp;
> struct xfs_dsb *sb;
> + struct xfs_perag *pag;
> xfs_agnumber_t agno;
> uint32_t v2_ok;
> __be32 features_mask;
> @@ -73,6 +74,15 @@ xchk_superblock(
> if (agno == 0)
> return 0;
>
> + /*
> + * Grab an active reference to the perag structure. If we can't get
> + * it, we're racing with something that's tearing down the AG, so
> + * signal that the AG no longer exists.
> + */
> + pag = xfs_perag_get(mp, agno);
> + if (!pag)
> + return -ENOENT;
> +
> error = xfs_sb_read_secondary(mp, sc->tp, agno, &bp);
> /*
> * The superblock verifier can return several different error codes
> @@ -92,7 +102,7 @@ xchk_superblock(
> break;
> }
> if (!xchk_process_error(sc, agno, XFS_SB_BLOCK(mp), &error))
> - return error;
> + goto out_pag;
>
> sb = bp->b_addr;
>
> @@ -336,7 +346,8 @@ xchk_superblock(
> xchk_block_set_corrupt(sc, bp);
>
> xchk_superblock_xref(sc, bp);
> -
> +out_pag:
> + xfs_perag_put(pag);
> return error;
> }
>
> @@ -527,6 +538,7 @@ xchk_agf(
> xchk_buffer_recheck(sc, sc->sa.agf_bp);
>
> agf = sc->sa.agf_bp->b_addr;
> + pag = sc->sa.pag;
>
> /* Check the AG length */
> eoag = be32_to_cpu(agf->agf_length);
> @@ -582,7 +594,6 @@ xchk_agf(
> xchk_block_set_corrupt(sc, sc->sa.agf_bp);
>
> /* Do the incore counters match? */
> - pag = xfs_perag_get(mp, agno);
> if (pag->pagf_freeblks != be32_to_cpu(agf->agf_freeblks))
> xchk_block_set_corrupt(sc, sc->sa.agf_bp);
> if (pag->pagf_flcount != be32_to_cpu(agf->agf_flcount))
> @@ -590,7 +601,6 @@ xchk_agf(
> if (xfs_sb_version_haslazysbcount(&sc->mp->m_sb) &&
> pag->pagf_btreeblks != be32_to_cpu(agf->agf_btreeblks))
> xchk_block_set_corrupt(sc, sc->sa.agf_bp);
> - xfs_perag_put(pag);
>
> xchk_agf_xref(sc);
> out:
> @@ -857,6 +867,7 @@ xchk_agi(
> xchk_buffer_recheck(sc, sc->sa.agi_bp);
>
> agi = sc->sa.agi_bp->b_addr;
> + pag = sc->sa.pag;
>
> /* Check the AG length */
> eoag = be32_to_cpu(agi->agi_length);
> @@ -909,12 +920,10 @@ xchk_agi(
> xchk_block_set_corrupt(sc, sc->sa.agi_bp);
>
> /* Do the incore counters match? */
> - pag = xfs_perag_get(mp, agno);
> if (pag->pagi_count != be32_to_cpu(agi->agi_count))
> xchk_block_set_corrupt(sc, sc->sa.agi_bp);
> if (pag->pagi_freecount != be32_to_cpu(agi->agi_freecount))
> xchk_block_set_corrupt(sc, sc->sa.agi_bp);
> - xfs_perag_put(pag);
>
> xchk_agi_xref(sc);
> out:
> diff --git a/fs/xfs/scrub/agheader_repair.c b/fs/xfs/scrub/agheader_repair.c
> index e95f8c98f0f7..f122f2e20e79 100644
> --- a/fs/xfs/scrub/agheader_repair.c
> +++ b/fs/xfs/scrub/agheader_repair.c
> @@ -366,7 +366,6 @@ xrep_agf(
> if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> return -EOPNOTSUPP;
>
> - xchk_perag_get(sc->mp, &sc->sa);
> /*
> * Make sure we have the AGF buffer, as scrub might have decided it
> * was corrupt after xfs_alloc_read_agf failed with -EFSCORRUPTED.
> @@ -641,7 +640,6 @@ xrep_agfl(
> if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> return -EOPNOTSUPP;
>
> - xchk_perag_get(sc->mp, &sc->sa);
> xbitmap_init(&agfl_extents);
>
> /*
> @@ -896,7 +894,6 @@ xrep_agi(
> if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> return -EOPNOTSUPP;
>
> - xchk_perag_get(sc->mp, &sc->sa);
> /*
> * Make sure we have the AGI buffer, as scrub might have decided it
> * was corrupt after xfs_ialloc_read_agi failed with -EFSCORRUPTED.
> diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c
> index 14e952d116f4..a5ca2856df8b 100644
> --- a/fs/xfs/scrub/bmap.c
> +++ b/fs/xfs/scrub/bmap.c
> @@ -260,7 +260,7 @@ xchk_bmap_iextent_xref(
> agbno = XFS_FSB_TO_AGBNO(mp, irec->br_startblock);
> len = irec->br_blockcount;
>
> - error = xchk_ag_init(info->sc, agno, &info->sc->sa);
> + error = xchk_ag_init_existing(info->sc, agno, &info->sc->sa);
> if (!xchk_fblock_process_error(info->sc, info->whichfork,
> irec->br_startoff, &error))
> return;
> diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
> index bd1172358964..c044e0a8da7f 100644
> --- a/fs/xfs/scrub/btree.c
> +++ b/fs/xfs/scrub/btree.c
> @@ -374,7 +374,7 @@ xchk_btree_check_block_owner(
>
> init_sa = bs->cur->bc_flags & XFS_BTREE_LONG_PTRS;
> if (init_sa) {
> - error = xchk_ag_init(bs->sc, agno, &bs->sc->sa);
> + error = xchk_ag_init_existing(bs->sc, agno, &bs->sc->sa);
> if (!xchk_btree_xref_process_error(bs->sc, bs->cur,
> level, &error))
> return error;
> diff --git a/fs/xfs/scrub/common.c b/fs/xfs/scrub/common.c
> index e86854171b0c..0ef96ed71017 100644
> --- a/fs/xfs/scrub/common.c
> +++ b/fs/xfs/scrub/common.c
> @@ -394,11 +394,11 @@ want_ag_read_header_failure(
> }
>
> /*
> - * Grab all the headers for an AG.
> + * Grab the perag structure and all the headers for an AG.
> *
> - * The headers should be released by xchk_ag_free, but as a fail
> - * safe we attach all the buffers we grab to the scrub transaction so
> - * they'll all be freed when we cancel it.
> + * The headers should be released by xchk_ag_free, but as a fail safe we attach
> + * all the buffers we grab to the scrub transaction so they'll all be freed
> + * when we cancel it. Returns ENOENT if we can't grab the perag structure.
> */
> int
> xchk_ag_read_headers(
> @@ -409,22 +409,26 @@ xchk_ag_read_headers(
> struct xfs_mount *mp = sc->mp;
> int error;
>
> + ASSERT(!sa->pag);
> + sa->pag = xfs_perag_get(mp, agno);
> + if (!sa->pag)
> + return -ENOENT;
> +
> sa->agno = agno;
>
> error = xfs_ialloc_read_agi(mp, sc->tp, agno, &sa->agi_bp);
> if (error && want_ag_read_header_failure(sc, XFS_SCRUB_TYPE_AGI))
> - goto out;
> + return error;
>
> error = xfs_alloc_read_agf(mp, sc->tp, agno, 0, &sa->agf_bp);
> if (error && want_ag_read_header_failure(sc, XFS_SCRUB_TYPE_AGF))
> - goto out;
> + return error;
>
> error = xfs_alloc_read_agfl(mp, sc->tp, agno, &sa->agfl_bp);
> if (error && want_ag_read_header_failure(sc, XFS_SCRUB_TYPE_AGFL))
> - goto out;
> - error = 0;
> -out:
> - return error;
> + return error;
> +
> + return 0;
> }
>
> /* Release all the AG btree cursors. */
> @@ -461,7 +465,6 @@ xchk_ag_btcur_init(
> {
> struct xfs_mount *mp = sc->mp;
>
> - xchk_perag_get(sc->mp, sa);
> if (sa->agf_bp &&
> xchk_ag_btree_healthy_enough(sc, sa->pag, XFS_BTNUM_BNO)) {
> /* Set up a bnobt cursor for cross-referencing. */
> @@ -532,11 +535,11 @@ xchk_ag_free(
> }
>
> /*
> - * For scrub, grab the AGI and the AGF headers, in that order. Locking
> - * order requires us to get the AGI before the AGF. We use the
> - * transaction to avoid deadlocking on crosslinked metadata buffers;
> - * either the caller passes one in (bmap scrub) or we have to create a
> - * transaction ourselves.
> + * For scrub, grab the perag structure, the AGI, and the AGF headers, in that
> + * order. Locking order requires us to get the AGI before the AGF. We use the
> + * transaction to avoid deadlocking on crosslinked metadata buffers; either the
> + * caller passes one in (bmap scrub) or we have to create a transaction
> + * ourselves. Returns ENOENT if the perag struct cannot be grabbed.
> */
> int
> xchk_ag_init(
> @@ -554,19 +557,6 @@ xchk_ag_init(
> return 0;
> }
>
> -/*
> - * Grab the per-ag structure if we haven't already gotten it. Teardown of the
> - * xchk_ag will release it for us.
> - */
> -void
> -xchk_perag_get(
> - struct xfs_mount *mp,
> - struct xchk_ag *sa)
> -{
> - if (!sa->pag)
> - sa->pag = xfs_perag_get(mp, sa->agno);
> -}
> -
> /* Per-scrubber setup functions */
>
> /*
> diff --git a/fs/xfs/scrub/common.h b/fs/xfs/scrub/common.h
> index 0410faf7d735..454145db10e7 100644
> --- a/fs/xfs/scrub/common.h
> +++ b/fs/xfs/scrub/common.h
> @@ -107,7 +107,23 @@ int xchk_setup_fscounters(struct xfs_scrub *sc);
> void xchk_ag_free(struct xfs_scrub *sc, struct xchk_ag *sa);
> int xchk_ag_init(struct xfs_scrub *sc, xfs_agnumber_t agno,
> struct xchk_ag *sa);
> -void xchk_perag_get(struct xfs_mount *mp, struct xchk_ag *sa);
> +
> +/*
> + * Grab all AG resources, treating the inability to grab the perag structure as
> + * a fs corruption. This is intended for callers checking an ondisk reference
> + * to a given AG, which means that the AG must still exist.
> + */
> +static inline int
> +xchk_ag_init_existing(
> + struct xfs_scrub *sc,
> + xfs_agnumber_t agno,
> + struct xchk_ag *sa)
> +{
> + int error = xchk_ag_init(sc, agno, sa);
> +
> + return error == -ENOENT ? -EFSCORRUPTED : error;
> +}
> +
> int xchk_ag_read_headers(struct xfs_scrub *sc, xfs_agnumber_t agno,
> struct xchk_ag *sa);
> void xchk_ag_btcur_free(struct xchk_ag *sa);
> diff --git a/fs/xfs/scrub/fscounters.c b/fs/xfs/scrub/fscounters.c
> index e03577af63d9..74e331afe49d 100644
> --- a/fs/xfs/scrub/fscounters.c
> +++ b/fs/xfs/scrub/fscounters.c
> @@ -146,7 +146,7 @@ xchk_fscount_btreeblks(
> xfs_extlen_t blocks;
> int error;
>
> - error = xchk_ag_init(sc, agno, &sc->sa);
> + error = xchk_ag_init_existing(sc, agno, &sc->sa);
> if (error)
> return error;
>
> diff --git a/fs/xfs/scrub/inode.c b/fs/xfs/scrub/inode.c
> index 76fbc7ca4cec..a6a68ba19f0a 100644
> --- a/fs/xfs/scrub/inode.c
> +++ b/fs/xfs/scrub/inode.c
> @@ -532,7 +532,7 @@ xchk_inode_xref(
> agno = XFS_INO_TO_AGNO(sc->mp, ino);
> agbno = XFS_INO_TO_AGBNO(sc->mp, ino);
>
> - error = xchk_ag_init(sc, agno, &sc->sa);
> + error = xchk_ag_init_existing(sc, agno, &sc->sa);
> if (!xchk_xref_process_error(sc, agno, agbno, &error))
> return;
>
--
chandan
