contpte_align_down
ptep = contpte_align_down(ptep);
ptep = contpte_align_down(ptep);
ptep = contpte_align_down(orig_ptep);
ptep = contpte_align_down(ptep);
if (ptep != contpte_align_down(ptep) || nr < CONT_PTES)
if (ptep + nr != contpte_align_down(ptep + nr)) {
pte_t *cont_ptep = contpte_align_down(ptep);
ptep = contpte_align_down(ptep);
start_ptep = ptep = contpte_align_down(ptep);