req_bp
xbdreq->req_bp = bp;
struct buf *req_bp; /* buffer associated with this request */
xbdreq2->req_bp = bp;
#define req_bp u.req_rw.req_bp
sc->sc_unalign_used = req->req_bp;
KASSERT(req->req_bp->b_bcount <= MAXPHYS);
if ((req->req_bp->b_flags & B_READ) == 0)
memcpy(req->req_data, req->req_bp->b_data,
req->req_bp->b_bcount);
KASSERT(xbdreq->req_bp == NULL);
bp = xbdreq->req_bp;
xbdreq->req_bp = NULL;