lookup_and_lock_node
err = lookup_and_lock_node(WRLOCK_NODE, nodeh, &nodep);
err = lookup_and_lock_node(RDLOCK_NODE, nodeh, &nodep); /* lock node */
err = lookup_and_lock_node(RDLOCK_NODE, nodeh, &nodep); /* lock node */
err = lookup_and_lock_node(WRLOCK_NODE, nodeh, &nodep); /* lock node */
err = lookup_and_lock_node(RDLOCK_NODE, nodeh, &nodep); /* lock node */
err = lookup_and_lock_node(RDLOCK_NODE, nodeh, &pobj); /* lock node */
err = lookup_and_lock_node(RDLOCK_NODE, rooth, &pobj); /* lock node */