NILFS_BMAP_SIZE
memset(bmap->b_u.u_data, 0, NILFS_BMAP_SIZE);
memcpy(bmap->b_u.u_data, raw_inode->i_bmap, NILFS_BMAP_SIZE);
memset(&bmap->b_u, 0, NILFS_BMAP_SIZE);
__le64 u_data[NILFS_BMAP_SIZE / sizeof(__le64)];
__le64 data[NILFS_BMAP_SIZE / sizeof(__le64)];
#define NILFS_BTREE_ROOT_SIZE NILFS_BMAP_SIZE
#define NILFS_DIRECT_NBLOCKS (NILFS_BMAP_SIZE / sizeof(__le64) - 1)