blwrite
void blwrite(int fd, char *buf, ufs2_daddr_t blk, ssize_t size);
blwrite(fd, bp->b_un.b_buf, bp->b_bno, bp->b_size);
blwrite(fswritefd, copybuf, fsbtodb(fs, blkno), fs->fs_bsize);
blwrite(fswritefd, copybuf, fsbtodb(fs, blkno), fs->fs_bsize);
blwrite(writefd, fsrbuf, (SBLOCK_UFS2 - rdsize) / dev_bsize, rdsize);