On Thu, Nov 05, 2015 at 12:10:13PM +0300, Vladimir Davydov wrote:
> On Tue, Nov 03, 2015 at 05:26:15PM +0200, Kirill A. Shutemov wrote:
> ...
> > @@ -56,23 +56,69 @@ static int page_idle_clear_pte_refs_one(struct page *page,
> > {
> > struct mm_struct *mm = vma->vm_mm;
> > spinlock_t *ptl;
> > + pgd_t *pgd;
> > + pud_t *pud;
> > pmd_t *pmd;
> > pte_t *pte;
> > bool referenced = false;
> >
> > - if (unlikely(PageTransHuge(page))) {
> > - pmd = page_check_address_pmd(page, mm, addr, &ptl);
> > - if (pmd) {
> > - referenced = pmdp_clear_young_notify(vma, addr, pmd);
> > + pgd = pgd_offset(mm, addr);
> > + if (!pgd_present(*pgd))
> > + return SWAP_AGAIN;
> > + pud = pud_offset(pgd, addr);
> > + if (!pud_present(*pud))
> > + return SWAP_AGAIN;
> > + pmd = pmd_offset(pud, addr);
> > +
> > + if (pmd_trans_huge(*pmd)) {
> > + ptl = pmd_lock(mm, pmd);
> > + if (!pmd_present(*pmd))
> > + goto unlock_pmd;
> > + if (unlikely(!pmd_trans_huge(*pmd))) {
> > spin_unlock(ptl);
> > + goto map_pte;
> > }
> > +
> > + if (pmd_page(*pmd) != page)
> > + goto unlock_pmd;
> > +
> > + referenced = pmdp_clear_young_notify(vma, addr, pmd);
> > + spin_unlock(ptl);
> > + goto found;
> > +unlock_pmd:
> > + spin_unlock(ptl);
> > + return SWAP_AGAIN;
> > } else {
> > - pte = page_check_address(page, mm, addr, &ptl, 0);
> > - if (pte) {
> > - referenced = ptep_clear_young_notify(vma, addr, pte);
> > - pte_unmap_unlock(pte, ptl);
> > - }
> > + pmd_t pmde = *pmd;
> > + barrier();
> > + if (!pmd_present(pmde) || pmd_trans_huge(pmde))
> > + return SWAP_AGAIN;
> > +
> > + }
> > +map_pte:
> > + pte = pte_offset_map(pmd, addr);
> > + if (!pte_present(*pte)) {
> > + pte_unmap(pte);
> > + return SWAP_AGAIN;
> > }
> > +
> > + ptl = pte_lockptr(mm, pmd);
> > + spin_lock(ptl);
> > +
> > + if (!pte_present(*pte)) {
> > + pte_unmap_unlock(pte, ptl);
> > + return SWAP_AGAIN;
> > + }
> > +
> > + /* THP can be referenced by any subpage */
> > + if (pte_pfn(*pte) - page_to_pfn(page) >= hpage_nr_pages(page)) {
> > + pte_unmap_unlock(pte, ptl);
> > + return SWAP_AGAIN;
> > + }
> > +
> > + referenced = ptep_clear_young_notify(vma, addr, pte);
> > + pte_unmap_unlock(pte, ptl);
> > +found:
>
> Can't we hide this stuff in a helper function, which would be used by
> both page_referenced_one and page_idle_clear_pte_refs_one, instead of
> duplicating page_referenced_one code here?
I would like to, but there's no obvious way to do that: PMDs and PTEs
require different handling.
Any ideas?
--
Kirill A. Shutemov
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