sdstrategy
err = physio(sdstrategy, NULL, dev, B_READ, sdmin, uio);
err = physio(sdstrategy, NULL, dev, B_WRITE, sdmin, uio);
err = aphysio(sdstrategy, anocancel, dev, B_READ, sdmin, aio);
err = aphysio(sdstrategy, anocancel, dev, B_WRITE, sdmin, aio);
sdstrategy, /* strategy */
static int sdstrategy(struct buf *bp);