xfs: attach dquots before performing xfs_swap_extents

Make sure we attach dquots to both inodes before swapping their extents.
This was found via manual code inspection by looking for places where we
could call xfs_trans_mod_dquot without dquots attached to inodes, and
confirmed by instrumenting the kernel and running xfs/328.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/xfs_bmap_util.c

@@ -1569,6 +1569,14 @@ xfs_swap_extents(
 		goto out_unlock;
 	}
 
+	error = xfs_qm_dqattach(ip);
+	if (error)
+		goto out_unlock;
+
+	error = xfs_qm_dqattach(tip);
+	if (error)
+		goto out_unlock;
+
 	error = xfs_swap_extent_flush(ip);
 	if (error)
 		goto out_unlock;