nilfs_btree_node
((NILFS_BTREE_ROOT_SIZE - sizeof(struct nilfs_btree_node)) / \
(((nodesize) - sizeof(struct nilfs_btree_node) - \
struct nilfs_btree_node *btree_hdr;
btree_hdr = (struct nilfs_btree_node *) bp->b_data;
sizeof(struct nilfs_btree_node) +
struct nilfs_btree_node *btree_hdr;
btree_hdr = (struct nilfs_btree_node *) &inode->i_bmap[0];