xfs: don't unconditionally clear the reflink flag on zero-block files

If we have speculative cow preallocations hanging around in the cow
fork, don't let a truncate operation clear the reflink flag because if
we do then there's a chance we'll forget to free those extents when we
destroy the incore inode.

Reported-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 5599dda4727a..4ec5b7f45401 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1624,10 +1624,12 @@ xfs_itruncate_extents(
                 goto out;
 
         /*
-         * Clear the reflink flag if we truncated everything.
+         * Clear the reflink flag if there are no data fork blocks and
+         * there are no extents staged in the cow fork.
          */
-        if (ip->i_d.di_nblocks == 0 && xfs_is_reflink_inode(ip)) {
-                ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
+        if (xfs_is_reflink_inode(ip) && ip->i_cnextents == 0) {
+                if (ip->i_d.di_nblocks == 0)
+                        ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
                 xfs_inode_clear_cowblocks_tag(ip);
         }