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

From: Miaohe Lin <linmiaohe@huawei.com>
To: Yang Shi <shy828301@gmail.com>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
	<vbabka@suse.cz>, <kirill.shutemov@linux.intel.com>,
	<willy@infradead.org>, <akpm@linux-foundation.org>
Subject: Re: [v3 PATCH 3/7] mm: khugepaged: remove the redundant anon vma check
Date: Fri, 10 Jun 2022 15:23:23 +0800	[thread overview]
Message-ID: <3f485480-9474-4401-bc4f-fb66aac1e591@huawei.com> (raw)
In-Reply-To: <20220606214414.736109-4-shy828301@gmail.com>

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@gmail.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;
>  }
>  
> 