linux-kernel - Re: [v3 PATCH 3/7] mm: khugepaged: remove the redundant anon vma check

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Date:   Fri, 10 Jun 2022 15:23:23 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Yang Shi <shy828301@...il.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <vbabka@...e.cz>, <kirill.shutemov@...ux.intel.com>,
        <willy@...radead.org>, <akpm@...ux-foundation.org>
Subject: Re: [v3 PATCH 3/7] mm: khugepaged: remove the redundant anon vma
 check

On 2022/6/7 5:44, Yang Shi wrote:
> The hugepage_vma_check() already checked it, so remove the redundant
> check.
> 
> Signed-off-by: Yang Shi <shy828301@...il.com>
> ---
>  mm/khugepaged.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index d0f8020164fc..7a5d1c1a1833 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -966,9 +966,6 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
>  		return SCAN_ADDRESS_RANGE;
>  	if (!hugepage_vma_check(vma, vma->vm_flags))
>  		return SCAN_VMA_CHECK;
> -	/* Anon VMA expected */
> -	if (!vma->anon_vma || !vma_is_anonymous(vma))
> -		return SCAN_VMA_CHECK;

Is it possible that hugepage_vma_check returns true due to the shmem check, or file thp check since
we dropped mmap_lock ? So anon vma is explicitly checked again here?

Thanks!

>  	return 0;
>  }
>  
>