BT_IS_ROOT
if (! BT_IS_ROOT((BTSTACK)->top->mp))\
(BT_IS_ROOT(MP) ? (TYPE *)&JFS_IP(IP)->ROOT : (TYPE *)(MP)->data)
if (BT_IS_ROOT(MP))\
if (! BT_IS_ROOT(MP)) \
if (BT_IS_ROOT(fmp)) {
if (BT_IS_ROOT(mp))