pmdp_huge_clear_flush
extern pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
(void)pmdp_huge_clear_flush(vma, haddr, vmf->pmd);
src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd);
old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd);
orig_pmd = pmdp_huge_clear_flush(vma, addr, pmdp);