Re: [RFC][PATCH v3 1/6] mm: Don't unmap gup()ed page
From: KOSAKI Motohiro
Date: Wed Apr 15 2009 - 07:39:21 EST
>> + if (!migration) {
>> + /* re-check */
>> + if (PageSwapCache(page) &&
>> + page_count(page) != page_mapcount(page) + 2) {
>> + /* We lose race against get_user_pages_fast() */
>> + set_pte_at(mm, address, pte, pteval);
>> + ret = SWAP_FAIL;
>> + goto out_unmap;
>> + }
>> + }
>> + mmu_notifier_invalidate_page(vma->vm_mm, address);
>
> With regard to mmu notifier, this is the opposite of the right
> ordering. One mmu_notifier_invalidate_page must run _before_ the first
> check. The ptep_clear_flush_notify will then stay and there's no need
> of a further mmu_notifier_invalidate_page after the second check.
OK. but I have one question.
Can we assume mmu_notifier is only used by kvm now?
if not, we need to make new notifier.
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