BD_RD
if ((rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD)) != 0) {
rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD);
rc = bd_io(dev, bd, dblk, x, bbuf, BD_RD);
bd_edd_io(bd, 0xffffffff, 1, (caddr_t)buf, BD_RD);
if (dowrite == BD_RD && dblk >= 0x100000000)