xfs: Check for extent overflow when renaming dir entries

Source kernel commit: 02092a2f034fdeabab524ae39c2de86ba9ffa15a

A rename operation is essentially a directory entry remove operation
from the perspective of parent directory (i.e. src_dp) of rename's
source. Hence the only place where we check for extent count overflow
for src_dp is in xfs_bmap_del_extent_real(). xfs_bmap_del_extent_real()
returns -ENOSPC when it detects a possible extent count overflow and in
response, the higher layers of directory handling code do the following:
1. Data/Free blocks: XFS lets these blocks linger until a future remove
operation removes them.
2. Dabtree blocks: XFS swaps the blocks with the last block in the Leaf
space and unmaps the last block.

For target_dp, there are two cases depending on whether the destination
directory entry exists or not.

When destination directory entry does not exist (i.e. target_ip ==
NULL), extent count overflow check is performed only when transaction
has a non-zero sized space reservation associated with it.  With a
zero-sized space reservation, XFS allows a rename operation to continue
only when the directory has sufficient free space in its data/leaf/free
space blocks to hold the new entry.

When destination directory entry exists (i.e. target_ip != NULL), all
we need to do is change the inode number associated with the already
existing entry. Hence there is no need to perform an extent count
overflow check.

Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index e3c6b0bbf2f41aa773205bade1c15dd68047b6b8..e9c9f45100df0a94b48249ef3b935991b5ce538f 100644 (file)
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -5153,6 +5153,9 @@ xfs_bmap_del_extent_real(
                 * until a future remove operation. Dabtree blocks would be
                 * swapped with the last block in the leaf space and then the
                 * new last block will be unmapped.
+                *
+                * The above logic also applies to the source directory entry of
+                * a rename operation.
                 */
                error = xfs_iext_count_may_overflow(ip, whichfork, 1);
                if (error) {