On Monday 9 November 2020 11:47:45 PM IST Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> 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.
>
The code changes are consistent with rules provided in the comments.
Reviewed-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
> Fixes: 08a3a692ef58 ("xfs: btree scrub should check minrecs")
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> 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 f52a7b8256f9..debf392e0515 100644
> --- a/fs/xfs/scrub/btree.c
> +++ b/fs/xfs/scrub/btree.c
> @@ -452,32 +452,41 @@ 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);
> }
>
> /*
>
>
--
chandan
