Commit 02092a2f authored by Chandan Babu R's avatar Chandan Babu R Committed by Darrick J. Wong
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xfs: Check for extent overflow when renaming dir entries 



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: default avatarChandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 0dbc5cb1

fs/xfs/libxfs/xfs_bmap.c

+3 −0
Original line number Diff line number Diff line
@@ -5160,6 +5160,9 @@ 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) {

fs/xfs/xfs_inode.c

+43 −1
Original line number Diff line number Diff line
@@ -3116,6 +3116,35 @@ xfs_rename( 
	/*

	 * Check for expected errors before we dirty the transaction

	 * so we can return an error without a transaction abort.

	 *

	 * Extent count overflow check:

	 *

	 * From the perspective of src_dp, a rename operation is essentially a

	 * directory entry remove operation. 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.

	 */

	if (target_ip == NULL) {

		/*
@@ -3126,6 +3155,12 @@ xfs_rename( 
			error = xfs_dir_canenter(tp, target_dp, target_name);

			if (error)

				goto out_trans_cancel;

		} else {

			error = xfs_iext_count_may_overflow(target_dp,

					XFS_DATA_FORK,

					XFS_IEXT_DIR_MANIP_CNT(mp));

			if (error)

				goto out_trans_cancel;

		}

	} else {

		/*
@@ -3291,9 +3326,16 @@ xfs_rename( 
	if (wip) {

		error = xfs_dir_replace(tp, src_dp, src_name, wip->i_ino,

					spaceres);

	} else

	} else {

		/*

		 * NOTE: We don't need to check for extent count overflow here

		 * because the dir remove name code will leave the dir block in

		 * place if the extent count would overflow.

		 */

		error = xfs_dir_removename(tp, src_dp, src_name, src_ip->i_ino,

					   spaceres);

	}



	if (error)

		goto out_trans_cancel;