From 02092a2f034fdeabab524ae39c2de86ba9ffa15a Mon Sep 17 00:00:00 2001 From: Chandan Babu R Date: Fri, 22 Jan 2021 16:48:13 -0800 Subject: 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: Chandan Babu R Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/xfs/libxfs/xfs_bmap.c | 3 +++ fs/xfs/xfs_inode.c | 44 +++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 46 insertions(+), 1 deletion(-) diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c index 6c8f17a0e247..8ebe5f13279c 100644 --- a/fs/xfs/libxfs/xfs_bmap.c +++ b/fs/xfs/libxfs/xfs_bmap.c @@ -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) { diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 3cb41b5d5a26..8ebd9c64aa48 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -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; -- cgit v1.2.3