ov_size
op->ov_size = roundup2(nbytes, RSLOP);
*(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
op->ov_size = roundup2(nbytes, RSLOP);
*(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;