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    SubjectRe: [patch 3/6] mmu_notifier: invalidate_page callbacks
    On Fri, 15 Feb 2008, Andrew Morton wrote:

    > > @@ -287,7 +288,8 @@ static int page_referenced_one(struct pa
    > > if (vma->vm_flags & VM_LOCKED) {
    > > referenced++;
    > > *mapcount = 1; /* break early from loop */
    > > - } else if (ptep_clear_flush_young(vma, address, pte))
    > > + } else if (ptep_clear_flush_young(vma, address, pte) |
    > > + mmu_notifier_age_page(mm, address))
    > > referenced++;
    >
    > The "|" is obviously deliberate. But no explanation is provided telling us
    > why we still call the callback if ptep_clear_flush_young() said the page
    > was recently referenced. People who read your code will want to understand
    > this.

    Andrea?

    > > flush_cache_page(vma, address, pte_pfn(*pte));
    > > entry = ptep_clear_flush(vma, address, pte);
    > > + mmu_notifier(invalidate_page, mm, address);
    >
    > I just don't see how ths can be done if the callee has another thread in
    > the middle of establishing IO against this region of memory.
    > ->invalidate_page() _has_ to be able to block. Confused.

    The page lock is held and that holds off I/O?



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