RSLOP
if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) {
n = -(sizeof (*op) + RSLOP);
op->ov_size = roundup2(nbytes, RSLOP);
onb -= sizeof (*op) + RSLOP;
onb += pagesz - sizeof (*op) - RSLOP;
i -= sizeof (*op) + RSLOP;
i += pagesz - sizeof (*op) - RSLOP;
op->ov_size = roundup2(nbytes, RSLOP);