Re: [RFC PATCH RESEND 08/28] mm/khugepaged: mark VMA as locked while collapsing a hugepage

[Laurent Dufour]

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@xxxxxxxxxx>
> ---
>  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,