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Message-ID: <389399bd-cf9f-4d6a-76fb-1fea1c05171e@suse.cz>
Date:   Mon, 9 May 2022 14:45:36 +0200
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Subject: Re: [v3 PATCH 2/8] mm: khugepaged: remove redundant check for
 VM_NO_KHUGEPAGED
Content-Language: en-US
To:     Yang Shi <shy828301@gmail.com>, kirill.shutemov@linux.intel.com,
        linmiaohe@huawei.com, songliubraving@fb.com, riel@surriel.com,
        willy@infradead.org, ziy@nvidia.com, tytso@mit.edu,
        akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220404200250.321455-1-shy828301@gmail.com>
 <20220404200250.321455-3-shy828301@gmail.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20220404200250.321455-3-shy828301@gmail.com>
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On 4/4/22 22:02, Yang Shi wrote:
> The hugepage_vma_check() called by khugepaged_enter_vma_merge() does
> check VM_NO_KHUGEPAGED. Remove the check from caller and move the check
> in hugepage_vma_check() up.
> 
> More checks may be run for VM_NO_KHUGEPAGED vmas, but MADV_HUGEPAGE is
> definitely not a hot path, so cleaner code does outweigh.
> 
> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
> Acked-by: Song Liu <song@kernel.org>
> Signed-off-by: Yang Shi <shy828301@gmail.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/khugepaged.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index a4e5eaf3eb01..7d197d9e3258 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -365,8 +365,7 @@ int hugepage_madvise(struct vm_area_struct *vma,
>  		 * register it here without waiting a page fault that
>  		 * may not happen any time soon.
>  		 */
> -		if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
> -				khugepaged_enter_vma_merge(vma, *vm_flags))
> +		if (khugepaged_enter_vma_merge(vma, *vm_flags))
>  			return -ENOMEM;
>  		break;
>  	case MADV_NOHUGEPAGE:
> @@ -445,6 +444,9 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
>  	if (!transhuge_vma_enabled(vma, vm_flags))
>  		return false;
>  
> +	if (vm_flags & VM_NO_KHUGEPAGED)
> +		return false;
> +
>  	if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
>  				vma->vm_pgoff, HPAGE_PMD_NR))
>  		return false;
> @@ -470,7 +472,8 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
>  		return false;
>  	if (vma_is_temporary_stack(vma))
>  		return false;
> -	return !(vm_flags & VM_NO_KHUGEPAGED);
> +
> +	return true;
>  }
>  
>  int __khugepaged_enter(struct mm_struct *mm)