[PATCH 4.9 40/48] xfs: always swap the cow forks when swapping extents

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Darrick J. Wong <darrick.w...@oracle.com>

commit 52bfcdd7adbc26639bc7b2356ab9a3f5dad68ad6 upstream.

Since the CoW fork exists as a secondary data structure to the data
fork, we must always swap cow forks during swapext.  We also need to
swap the extent counts and reset the cowblocks tags.

Reviewed-by: Brian Foster <bfos...@redhat.com>
Reviewed-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Darrick J. Wong <darrick.w...@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/xfs/xfs_bmap_util.c |   24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -2106,11 +2106,31 @@ xfs_swap_extents(
                ip->i_d.di_flags2 |= tip->i_d.di_flags2 & XFS_DIFLAG2_REFLINK;
                tip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
                tip->i_d.di_flags2 |= f & XFS_DIFLAG2_REFLINK;
+       }
+
+       /* Swap the cow forks. */
+       if (xfs_sb_version_hasreflink(&mp->m_sb)) {
+               xfs_extnum_t    extnum;
+
+               ASSERT(ip->i_cformat == XFS_DINODE_FMT_EXTENTS);
+               ASSERT(tip->i_cformat == XFS_DINODE_FMT_EXTENTS);
+
+               extnum = ip->i_cnextents;
+               ip->i_cnextents = tip->i_cnextents;
+               tip->i_cnextents = extnum;
+
                cowfp = ip->i_cowfp;
                ip->i_cowfp = tip->i_cowfp;
                tip->i_cowfp = cowfp;
-               xfs_inode_set_cowblocks_tag(ip);
-               xfs_inode_set_cowblocks_tag(tip);
+
+               if (ip->i_cowfp && ip->i_cnextents)
+                       xfs_inode_set_cowblocks_tag(ip);
+               else
+                       xfs_inode_clear_cowblocks_tag(ip);
+               if (tip->i_cowfp && tip->i_cnextents)
+                       xfs_inode_set_cowblocks_tag(tip);
+               else
+                       xfs_inode_clear_cowblocks_tag(tip);
        }
 
        xfs_trans_log_inode(tp, ip,  src_log_flags);