On Thu, Nov 05, 2015 at 03:53:54PM +0300, Vladimir Davydov wrote:
> On Thu, Nov 05, 2015 at 02:36:06PM +0200, Kirill A. Shutemov wrote:
> > On Thu, Nov 05, 2015 at 03:07:26PM +0300, Vladimir Davydov wrote:
> > > @@ -849,30 +836,23 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
> > > if (pmd_page(*pmd) != page)
> > > goto unlock_pmd;
> > >
> > > - if (vma->vm_flags & VM_LOCKED) {
> > > - pra->vm_flags |= VM_LOCKED;
> > > - ret = SWAP_FAIL; /* To break the loop */
> > > - goto unlock_pmd;
> > > - }
> > > -
> > > - if (pmdp_clear_flush_young_notify(vma, address, pmd))
> > > - referenced++;
> > > - spin_unlock(ptl);
> > > + pte = (pte_t *)pmd;
> >
> > pmd_t and pte_t are not always compatible. We shouldn't pretend they are.
> > And we shouldn't use pte_unmap_unlock() to unlock pmd table.
>
> Out of curiosity, is it OK that __page_check_address can call
> pte_unmap_unlock on pte returned by huge_pte_offset, which isn't really
> pte, but pmd or pud?
hugetlb is usually implemented on architectures where you can expect some
level of compatibility between page table enties on different levels.
> > What about interface like this (I'm not sure about helper's name):
> >
> > void page_check_address_transhuge(struct page *page, struct mm_struct *mm,
> > unsigned long address,
> > pmd_t **pmdp, pte_t **ptep,
> > spinlock_t **ptlp);
> >
> > page_check_address_transhuge(page, mm, address, &pmd, &pte, &ptl);
> > if (pmd) {
> > /* handle pmd... */
> > } else if (pte) {
> > /* handle pte... */
> > } else {
> > return SWAP_AGAIN;
> > }
> >
> > /* common stuff */
> >
> > if (pmd)
> > spin_unlock(ptl);
> > else
> > pte_unmap_unlock(pte, ptl);
>
> spin_unlock(ptl);
> if (pte)
> pte_unmap(pte);
>
> would look neater IMO. Other than that, I think it's OK. At least, it
> looks better and less error-prone than duplicating such a huge chunk of
> code IMO.
Okay. Could you prepare the patch?
--
Kirill A. Shutemov
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