bioclone
bp = bioclone(fdb->fd_parentbp, off, len, 0, 0,
rbp = bioclone(bp, io_off, (size_t)contig,
cb = bioclone(pb, offset, pbcount, dev,
new_bp = bioclone(bp, 0, datalen, SD_GET_DEV(un), blkno, func,
bp = bioclone(bp0, brkp->off, brkp->brksize,
bp = bioclone(bp0, brkp->off,
struct buf *bioclone(struct buf *, off_t, size_t, dev_t, daddr_t,