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.

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);

/* ... */

The helper shouldn't set pmd if the page is tracked to pte.

-- 
 Kirill A. Shutemov
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