pte_offset_map_ro_nolock
pte = pte_offset_map_ro_nolock(mm, pmd, addr, &ptl);
pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
ptep = pte_offset_map_ro_nolock(vma->vm_mm, vmf->pmd, vmf->address,
pte = pte_offset_map_ro_nolock(mm, pmd, addr, &ptl);