[PATCH 6.6 1/8] xfs: fix imprecise logic in xchk_btree_check_block_owner

Catherine Hoang
2024-06-17T23:04:02Z

From: "Darrick J. Wong" <djwong@kernel.org>

commit c0afba9a8363f17d4efed22a8764df33389aebe8 upstream.

A reviewer was confused by the init_sa logic in this function. Upon
checking the logic, I discovered that the code is imprecise. What we
want to do here is check that there is an ownership record in the rmap
btree for the AG that contains a btree block.

For an inode-rooted btree (e.g. the bmbt) the per-AG btree cursors have
not been initialized because inode btrees can span multiple AGs.
Therefore, we must initialize the per-AG btree cursors in sc->sa before
proceeding. That is what init_sa controls, and hence the logic should
be gated on XFS_BTREE_ROOT_IN_INODE, not XFS_BTREE_LONG_PTRS.

In practice, ROOT_IN_INODE and LONG_PTRS are coincident so this hasn't
mattered. However, we're about to refactor both of those flags into
separate btree_ops fields so we want this the logic to make sense
afterwards.

Fixes: 858333dcf021a ("xfs: check btree block ownership with bnobt/rmapbt when scrubbing btree")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/scrub/btree.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
index 1935b9ce1885..c3a9f33e5a8d 100644
--- a/fs/xfs/scrub/btree.c
+++ b/fs/xfs/scrub/btree.c
@@ -385,7 +385,12 @@ xchk_btree_check_block_owner(
agno = xfs_daddr_to_agno(bs->cur->bc_mp, daddr);
agbno = xfs_daddr_to_agbno(bs->cur->bc_mp, daddr);

- init_sa = bs->cur->bc_flags & XFS_BTREE_LONG_PTRS;
+ /*
+ * If the btree being examined is not itself a per-AG btree, initialize
+ * sc->sa so that we can check for the presence of an ownership record
+ * in the rmap btree for the AG containing the block.
+ */
+ init_sa = bs->cur->bc_flags & XFS_BTREE_ROOT_IN_INODE;
if (init_sa) {
error = xchk_ag_init_existing(bs->sc, agno, &bs->sc->sa);
if (!xchk_btree_xref_process_error(bs->sc, bs->cur,
--
2.39.3