linux-kernel - Re: [PATCH v2 3/3] mm: memory-hotplug: check folio ref count first in do_migrate

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Message-ID: <5e2314ac-078b-444b-8142-057a005bbe07@huawei.com>
Date: Mon, 20 Jan 2025 17:11:06 +0800
From: mawupeng <mawupeng1@...wei.com>
To: <david@...hat.com>, <akpm@...ux-foundation.org>, <osalvador@...e.de>,
	<nao.horiguchi@...il.com>, <linmiaohe@...wei.com>, <mhocko@...e.com>
CC: <mawupeng1@...wei.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] mm: memory-hotplug: check folio ref count first in
 do_migrate_rang



On 2025/1/20 16:01, David Hildenbrand wrote:
> On 16.01.25 07:16, Wupeng Ma wrote:
>> From: Ma Wupeng <mawupeng1@...wei.com>
>>
>> If a folio has an increased reference count, folio_try_get() will acquire
>> it, perform necessary operations, and then release it. In the case of a
>> poisoned folio without an elevated reference count (which is unlikely for
>> memory-failure), folio_try_get() will simply bypass it.
>>
>> Therefore, relocate the folio_try_get() function, responsible for checking
>> and acquiring this reference count at first.
>>
>> Signed-off-by: Ma Wupeng <mawupeng1@...wei.com>
>> ---
>>   mm/memory_hotplug.c | 14 ++++----------
>>   1 file changed, 4 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 2815bd4ea483..3fb75ee185c6 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1786,6 +1786,9 @@ static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
>>           page = pfn_to_page(pfn);
>>           folio = page_folio(page);
>>   +        if (!folio_try_get(folio))
>> +            continue;
>> +
> 
> I would only move it in front of the folio_test_hwpoison() check for now. Note that with this patch as is the comment below would be wrong

Thanks for notice this.

Move it in front of the folio_test_hwpoison() do seems better.

> 
>>           /*
>>            * No reference or lock is held on the folio, so it might
> 
> ^
> 
> I would move this patch before the current #2, so the folio_lock() looks less weird.
> 

Ok, will be done.

Thanks.