linux-kernel - Re: [PATCH] mm/rmap: vm_flags including VM

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Message-ID: <a1357e75-986a-4e00-a987-9d8c767a42a5@redhat.com>
Date:   Tue, 24 Oct 2023 17:51:47 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Zhiguo Jiang <justinjiang@...o.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     opensource.kernel@...o.com
Subject: Re: [PATCH] mm/rmap: vm_flags including VM_EXEC can exit timely

On 24.10.23 16:49, Zhiguo Jiang wrote:
> When pra->vm_flags include VM_EXEC flag and folio is file detected in
> folio_referenced_one(), the folio referenced traversal process can be
> exited timely to reduce the detecting folio referenced time.
> 

Can you further elaborate what the logic behind that is?

Why can we stop here if we're dealing with a pagecache folio in an 
executable VMA?

> Signed-off-by: Zhiguo Jiang <justinjiang@...o.com>
> ---
>   mm/rmap.c | 2 ++
>   1 file changed, 2 insertions(+)
>   mode change 100644 => 100755 mm/rmap.c
> 
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 7a27a2b41802..932f3b7e8521
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -884,6 +884,8 @@ static bool folio_referenced_one(struct folio *folio,
>   	if (referenced) {
>   		pra->referenced++;
>   		pra->vm_flags |= vma->vm_flags & ~VM_LOCKED;
> +		if ((pra->vm_flags | VM_EXEC) && folio_is_file_lru(folio))
> +			return false;
>   	}
>   
>   	if (!pra->mapcount)

-- 
Cheers,

David / dhildenb