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Subject: Re: [PATCH] mm/gup: don't check page lru flag before draining it
To: Baolin Wang <baolin.wang@linux.alibaba.com>, akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, liuzixing@hygon.cn
References: <1717488551-18053-1-git-send-email-yangge1116@126.com>
 <89bd659b-a85f-48f2-98ce-f7522cdb95da@linux.alibaba.com>
From: yangge1116 <yangge1116@126.com>
Message-ID: <b61ee830-0833-e8ca-4c23-f83823b04d2e@126.com>
Date: Tue, 4 Jun 2024 17:18:57 +0800
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在 2024/6/4 下午4:56, Baolin Wang 写道:
> 
> 
> On 2024/6/4 16:09, yangge1116@126.com wrote:
>> From: yangge <yangge1116@126.com>
>>
>> If a page is added in pagevec, its ref count increases one, remove
>> the page from pagevec decreases one. Page migration requires the
>> page is not referrened by others except page mapping. Before
>> migrating a page, we should try to drain the page from pagevec in
>> case the page is in it, however, folio_test_lru() is not sufficient
>> to tell whether the page is in pagevec or not, if the page is in
>> pagevec, the migration will fail.
>>
>> Remove the condition and drain lru once to ensure the page is not
>> referrenced by pagevec.
> 
> This looks sane to me and seems a simple way to fix.
> 
>> Signed-off-by: yangge <yangge1116@126.com>
>> ---
>>   mm/gup.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/gup.c b/mm/gup.c
>> index ca0f5ce..890dcbc 100644
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -2411,7 +2411,7 @@ static unsigned long 
>> collect_longterm_unpinnable_pages(
>>               continue;
>>           }
>> -        if (!folio_test_lru(folio) && drain_allow) {
>> +        if (drain_allow) {
>>               lru_add_drain_all();
>>               drain_allow = false;
>>           }
> 
> You should rebase your code on the latest mm-unstable branch, as 
> collect_longterm_unpinnable_pages() in the upstream has been replaced 
> with collect_longterm_unpinnable_folios().
Ok, thanks