linux-kernel - Re: [PATCH 5/8] mm/vmscan: use helper folio_is_file

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Message-ID: <191fa86c-2548-d136-19f5-3e0a744b6da9@huawei.com>
Date:   Fri, 1 Apr 2022 14:14:49 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     "Huang, Ying" <ying.huang@...el.com>
CC:     <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Konstantin Khlebnikov <khlebnikov@...nvz.org>,
        Wu Fengguang <wfg@...l.ustc.edu.cn>
Subject: Re: [PATCH 5/8] mm/vmscan: use helper folio_is_file_lru()

On 2022/4/1 11:20, Huang, Ying wrote:
> Miaohe Lin <linmiaohe@...wei.com> writes:
> 
>> Use helper folio_is_file_lru() to check whether folio is file lru. Minor
>> readability improvement.
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>> ---
>>  mm/vmscan.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index ebd8ffb63673..31e95d627448 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1411,14 +1411,14 @@ static enum page_references folio_check_references(struct folio *folio,
>>  		/*
>>  		 * Activate file-backed executable folios after first usage.
>>  		 */
>> -		if ((vm_flags & VM_EXEC) && !folio_test_swapbacked(folio))
>> +		if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
> 
> I think that this should be converted to
> 
> 		if ((vm_flags & VM_EXEC)))
> 
> We should activate swap-backed executable folios (e.g. tmpfs) after
> first usage too.
> 

Dig into the git history, we can found that commit c909e99364c8 ("vmscan: activate executable pages after first usage")
activate swap-backed executable folios after first usage too. But later swap-backed executable folios is not activated
via commit b518154e59aa ("mm/vmscan: protect the workingset on anonymous LRU") to pretect the workingset from anonymous
LRU. So above change might not be wanted. Or am I miss something?

Many thanks.

> Best Regards,
> Huang, Ying
> 
>>  			return PAGEREF_ACTIVATE;
>>  
>>  		return PAGEREF_KEEP;
>>  	}
>>  
>>  	/* Reclaim if clean, defer dirty folios to writeback */
>> -	if (referenced_folio && !folio_test_swapbacked(folio))
>> +	if (referenced_folio && folio_is_file_lru(folio))
>>  		return PAGEREF_RECLAIM_CLEAN;
>>  
>>  	return PAGEREF_RECLAIM;
> .
>