pmd_mkinvalid
prot = pmd_pgprot(pmd_mkinvalid(pfn_pmd(0, prot)));
new_pmd = pmd_mkinvalid(*pmd);
return pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp));
WARN_ON(!pmd_trans_huge(pmd_mkinvalid(pmd_mkhuge(pmd))));
WARN_ON(!pmd_present(pmd_mkinvalid(pmd_mkhuge(pmd))));
WARN_ON(!pmd_leaf(pmd_mkinvalid(pmd_mkhuge(pmd))));
pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp));