FOLL_SPLIT_PMD
unsigned int gup_flags = FOLL_FORCE|FOLL_SPLIT_PMD;
gup_flags |= FOLL_WRITE | FOLL_SPLIT_PMD;
gup_flags |= FOLL_WRITE | FOLL_SPLIT_PMD;
if ((gup_flags & FOLL_SPLIT_PMD) && is_vm_hugetlb_page(vma))
if (pmd_trans_huge(pmdval) && (flags & FOLL_SPLIT_PMD)) {
FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,