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SubjectRe: [RFC PATCH RESEND 08/28] mm/khugepaged: mark VMA as locked while collapsing a hugepage
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Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit :
> Protect VMA from concurrent page fault handler while modifying it in
> collapse_huge_page.

Is the goal to protect changes in the anon_vma structure?

AFAICS, the vma it self is not impacted here, only the anon_vma and the
PMD/PTE are touched, and they have their own protection mechanism, isn't it?

>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
> mm/khugepaged.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 01f71786d530..030680633989 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1072,6 +1072,7 @@ static void collapse_huge_page(struct mm_struct *mm,
> if (mm_find_pmd(mm, address) != pmd)
> goto out_up_write;
>
> + vma_mark_locked(vma);
> anon_vma_lock_write(vma->anon_vma);
>
> mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm,

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