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

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Date:   Fri, 01 Apr 2022 14:40:36 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Miaohe Lin <linmiaohe@...wei.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        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()

Miaohe Lin <linmiaohe@...wei.com> writes:

> 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?

I think we should restore the original behavior to protect swap backed
executable folios too.

Hi, Kim,

What do you think about this?

Best Regards,
Huang, Ying

> 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;
>> .
>>