ext2fs_setnblock
ext2fs_setnblock(ip, ext2fs_nblock(ip) + btodb(fs->e2fs_bsize));
ext2fs_setnblock(ip, ext2fs_nblock(ip) - btodb(deallocated));
int ext2fs_setnblock(struct inode *, uint64_t);
error = ext2fs_setnblock(oip, ext2fs_nblock(oip) - blocksreleased);
(void)ext2fs_setnblock(ip, 0);