BFS_BSHIFT
filesize = partsize << BFS_BSHIFT;
mp->mnt_dev_bshift = BFS_BSHIFT;
mp->mnt_fs_bshift = BFS_BSHIFT;
data_block = (bfs->data_end - bfs->data_start) >> BFS_BSHIFT;
free_block = (bfs->data_end >> BFS_BSHIFT) - free_block;