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

BugLink: http://bugs.launchpad.net/bugs/1731951
commit cc6f77710a6de6210f9feda7cd53e2f5ee7a7e69 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 97045e8dfed5f9529931ffc72b9bec5442cfc5de..cd2e5b122b0110b9da77ba607505712097cb5dbd 100644 (file)
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1623,10 +1623,12 @@ 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);
        }