xfs: create a new buf_ops pointer to verify structure metadata

Expose all metadata structure buffer verifier functions via buf_ops.
These will be used by the online scrub mechanism to look for problems
with buffers that are already sitting around in memory.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_dir2_node.c

@@ -164,6 +164,7 @@ const struct xfs_buf_ops xfs_dir3_free_buf_ops = {
 	.name = "xfs_dir3_free",
 	.verify_read = xfs_dir3_free_read_verify,
 	.verify_write = xfs_dir3_free_write_verify,
+	.verify_struct = xfs_dir3_free_verify,
 };
 
 /* Everything ok in the free block header? */