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xfs: snapshot old AGFL before rewriting it

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LOLLM complains that we can't undo an attempt at fixing the AGFL if
anything goes wrong during the rewrite, so take a snapshot of the whole
buffer so that we can restore it.  Move the xrep_agfl_update_agf call so
that we only update the AGF if the AGFL update is 100% successful.

While we're at it, fix leaking the used_extents bitmap if the disunion
operation fails.

Cc: stable@vger.kernel.org # v4.19
Fixes: 0e93d3f43e ("xfs: repair the AGFL")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Assisted-by: LOLLM # finding obvious bugs
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
This commit is contained in:
Darrick J. Wong 2026-09-08 23:04:04 -07:00 committed by Carlos Maiolino
parent 341f03865d
commit 3466dfef0a
1 changed files with 25 additions and 10 deletions
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35
fs/xfs/scrub/agheader_repair.c
View File

@ -668,14 +668,16 @@ xrep_agfl_init_header(
struct xfs_scrub *sc,
struct xfs_buf *agfl_bp,
struct xagb_bitmap *agfl_extents,
xfs_agblock_t flcount)
xfs_agblock_t flcount,
struct xfs_agfl *old_agfl)
{
struct xrep_agfl_fill af = {
.sc = sc,
.flcount = flcount,
};
struct xfs_mount *mp = sc->mp;
struct xfs_agfl *agfl;
struct xfs_agfl *agfl = XFS_BUF_TO_AGFL(agfl_bp);
const size_t agfl_sz = BBTOB(agfl_bp->b_length);
int error;
ASSERT(flcount <= xfs_agfl_size(mp));
@ -684,8 +686,8 @@ xrep_agfl_init_header(
* Start rewriting the header by setting the bno[] array to
* NULLAGBLOCK, then setting AGFL header fields.
*/
agfl = XFS_BUF_TO_AGFL(agfl_bp);
memset(agfl, 0xFF, BBTOB(agfl_bp->b_length));
memcpy(old_agfl, agfl, agfl_sz);
memset(agfl, 0xFF, agfl_sz);
agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
agfl->agfl_seqno = cpu_to_be32(pag_agno(sc->sa.pag));
uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);
@ -700,13 +702,18 @@ xrep_agfl_init_header(
xagb_bitmap_walk(agfl_extents, xrep_agfl_fill, &af);
error = xagb_bitmap_disunion(agfl_extents, &af.used_extents);
if (error)
return error;
goto err_undo;
/* Write new AGFL to disk. */
xfs_trans_buf_set_type(sc->tp, agfl_bp, XFS_BLFT_AGFL_BUF);
xfs_trans_log_buf(sc->tp, agfl_bp, 0, BBTOB(agfl_bp->b_length) - 1);
xfs_trans_log_buf(sc->tp, agfl_bp, 0, agfl_sz - 1);
xagb_bitmap_destroy(&af.used_extents);
return 0;
err_undo:
xagb_bitmap_destroy(&af.used_extents);
memcpy(agfl, old_agfl, agfl_sz);
return error;
}
/* Repair the AGFL. */
@ -718,6 +725,7 @@ xrep_agfl(
struct xfs_mount *mp = sc->mp;
struct xfs_buf *agf_bp;
struct xfs_buf *agfl_bp;
struct xfs_agfl *old_agfl;
xfs_agblock_t flcount;
int error;
@ -725,6 +733,10 @@ xrep_agfl(
if (!xfs_has_rmapbt(mp))
return -EOPNOTSUPP;
old_agfl = kzalloc(BBTOB(XFS_FSS_TO_BB(mp, 1)), XCHK_GFP_FLAGS);
if (!old_agfl)
return -ENOMEM;
xagb_bitmap_init(&agfl_extents);
/*
@ -734,7 +746,7 @@ xrep_agfl(
*/
error = xfs_alloc_read_agf(sc->sa.pag, sc->tp, 0, &agf_bp);
if (error)
return error;
goto err_old_agfl;
/*
* Make sure we have the AGFL buffer, as scrub might have decided it
@ -745,7 +757,7 @@ xrep_agfl(
XFS_AGFL_DADDR(mp)),
XFS_FSS_TO_BB(mp, 1), 0, &agfl_bp, NULL);
if (error)
return error;
goto err_old_agfl;
agfl_bp->b_ops = &xfs_agfl_buf_ops;
/* Gather all the extents we're going to put on the new AGFL. */
@ -762,10 +774,11 @@ xrep_agfl(
* we adjust the AGF flcount (which can fail) so avoid updating any
* buffers until we know that part works.
*/
xrep_agfl_update_agf(sc, agf_bp, flcount);
error = xrep_agfl_init_header(sc, agfl_bp, &agfl_extents, flcount);
error = xrep_agfl_init_header(sc, agfl_bp, &agfl_extents, flcount,
old_agfl);
if (error)
goto err;
xrep_agfl_update_agf(sc, agf_bp, flcount);
/*
* Ok, the AGFL should be ready to go now. Roll the transaction to
@ -785,6 +798,8 @@ xrep_agfl(
err:
xagb_bitmap_destroy(&agfl_extents);
err_old_agfl:
kfree(old_agfl);
return error;
}