[PATCH 4.19 59/91] xfs: fix the minrecs logic when dealing with inode root child blocks

Greg Kroah-Hartman
2020-11-23T13:27:25Z

From: Darrick J. Wong <darrick.wong@oracle.com>

[ Upstream commit e95b6c3ef1311dd7b20467d932a24b6d0fd88395 ]

The comment and logic in xchk_btree_check_minrecs for dealing with
inode-rooted btrees isn't quite correct. While the direct children of
the inode root are allowed to have fewer records than what would
normally be allowed for a regular ondisk btree block, this is only true
if there is only one child block and the number of records don't fit in
the inode root.

Fixes: 08a3a692ef58 ("xfs: btree scrub should check minrecs")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/xfs/scrub/btree.c | 45 ++++++++++++++++++++++++++------------------
1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
index 4ae959f7ad2c0..c924fe3cdad65 100644
--- a/fs/xfs/scrub/btree.c
+++ b/fs/xfs/scrub/btree.c
@@ -450,32 +450,41 @@ xchk_btree_check_minrecs(
int level,
struct xfs_btree_block *block)
{
- unsigned int numrecs;
- int ok_level;
-
- numrecs = be16_to_cpu(block->bb_numrecs);
+ struct xfs_btree_cur *cur = bs->cur;
+ unsigned int root_level = cur->bc_nlevels - 1;
+ unsigned int numrecs = be16_to_cpu(block->bb_numrecs);

/* More records than minrecs means the block is ok. */
- if (numrecs >= bs->cur->bc_ops->get_minrecs(bs->cur, level))
+ if (numrecs >= cur->bc_ops->get_minrecs(cur, level))
return;

/*
- * Certain btree blocks /can/ have fewer than minrecs records. Any
- * level greater than or equal to the level of the highest dedicated
- * btree block are allowed to violate this constraint.
- *
- * For a btree rooted in a block, the btree root can have fewer than
- * minrecs records. If the btree is rooted in an inode and does not
- * store records in the root, the direct children of the root and the
- * root itself can have fewer than minrecs records.
+ * For btrees rooted in the inode, it's possible that the root block
+ * contents spilled into a regular ondisk block because there wasn't
+ * enough space in the inode root. The number of records in that
+ * child block might be less than the standard minrecs, but that's ok
+ * provided that there's only one direct child of the root.
*/
- ok_level = bs->cur->bc_nlevels - 1;
- if (bs->cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)
- ok_level--;
- if (level >= ok_level)
+ if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
+ level == cur->bc_nlevels - 2) {
+ struct xfs_btree_block *root_block;
+ struct xfs_buf *root_bp;
+ int root_maxrecs;
+
+ root_block = xfs_btree_get_block(cur, root_level, &root_bp);
+ root_maxrecs = cur->bc_ops->get_dmaxrecs(cur, root_level);
+ if (be16_to_cpu(root_block->bb_numrecs) != 1 ||
+ numrecs <= root_maxrecs)
+ xchk_btree_set_corrupt(bs->sc, cur, level);
return;
+ }

- xchk_btree_set_corrupt(bs->sc, bs->cur, level);
+ /*
+ * Otherwise, only the root level is allowed to have fewer than minrecs
+ * records or keyptrs.
+ */
+ if (level < root_level)
+ xchk_btree_set_corrupt(bs->sc, cur, level);
}

/*
--
2.27.0