XFR_PARITY_BLOCK
rqe->flags = (m.flags | XFR_PARITY_BLOCK | XFR_MALLOCED) /* always malloc parity block */
if ((rqe->flags & (XFR_NORMAL_WRITE | XFR_PARITY_BLOCK))
== (XFR_NORMAL_WRITE | XFR_PARITY_BLOCK)) { /* case 3 */