diff mbox series

[2/4] xfs: fix the minrecs logic when dealing with inode root child blocks

Message ID 160494586556.772802.12631379595730474933.stgit@magnolia (mailing list archive)
State Accepted
Headers show
Series xfs: fix various scrub problems | expand

Commit Message

Darrick J. Wong Nov. 9, 2020, 6:17 p.m. UTC 
From: Darrick J. Wong <darrick.wong@oracle.com>

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>
---
 fs/xfs/scrub/btree.c |   45 +++++++++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 18 deletions(-)

Comments

Chandan Babu R Nov. 13, 2020, 6:35 a.m. UTC | #1 
On Monday 9 November 2020 11:47:45 PM IST Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> 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@gmail.com>

> Fixes: 08a3a692ef58 ("xfs: btree scrub should check minrecs")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  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);
>  }
>  
>  /*
> 
>
Christoph Hellwig Nov. 14, 2020, 10:39 a.m. UTC | #2 
On Mon, Nov 09, 2020 at 10:17:45AM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> 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>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

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);
 }
 
 /*