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From: Wei Yang <richardw.yang@linux.intel.com>
To: David Hildenbrand <david@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>,
	n-horiguchi@ah.jp.nec.com, akpm@linux-foundation.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm/memory-failure.c: PageHuge is handled at the beginning of memory_failure
Date: Wed, 20 Nov 2019 08:46:20 +0800
Message-ID: <20191120004620.GB11061@richard> (raw)
In-Reply-To: <1e61c115-5787-9ef4-a449-2e490c53fca7@redhat.com>

On Tue, Nov 19, 2019 at 01:23:54PM +0100, David Hildenbrand wrote:
>On 18.11.19 09:20, Wei Yang wrote:
>> PageHuge is handled by memory_failure_hugetlb(), so this case could be
>> removed.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>> ---
>>   mm/memory-failure.c | 5 +----
>>   1 file changed, 1 insertion(+), 4 deletions(-)
>> 
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 3151c87dff73..392ac277b17d 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -1359,10 +1359,7 @@ int memory_failure(unsigned long pfn, int flags)
>>   	 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
>>   	 * correctly, we save a copy of the page flags at this time.
>>   	 */
>> -	if (PageHuge(p))
>> -		page_flags = hpage->flags;
>> -	else
>> -		page_flags = p->flags;
>> +	page_flags = p->flags;
>>   	/*
>>   	 * unpoison always clear PG_hwpoison inside page lock
>> 
>
>I somewhat miss a proper explanation why this is safe to do. We access page
>flags here, so why is it safe to refer to the ones of the sub-page?
>

Hi, David

I think your comment is on this line:

	page_flags = p->flags;

Maybe we need to use this:

	page_flags = hpage->flags;

And use hpage in the following or even the whole function?

While one thing interesting is not all "compound page" is PageCompound. For
some sub-page, we can't get the correct head. This means we may just check on
the sub-page.

>-- 
>
>Thanks,
>
>David / dhildenb

-- 
Wei Yang
Help you, Help me


  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-18  8:20 Wei Yang
2019-11-18  8:20 ` [PATCH 2/2] mm/memory-failure.c: not necessary to recalculate hpage Wei Yang
2019-11-20 15:07   ` David Hildenbrand
2019-11-21  1:05     ` Wei Yang
2019-12-02 22:28     ` Wei Yang
2019-12-05 15:06       ` David Hildenbrand
2019-12-06  1:48         ` Wei Yang
2020-01-08 12:20           ` David Hildenbrand
2020-01-09  1:58             ` Wei Yang
2019-11-19 12:23 ` [PATCH 1/2] mm/memory-failure.c: PageHuge is handled at the beginning of memory_failure David Hildenbrand
2019-11-20  0:46   ` Wei Yang [this message]
2019-11-20 15:04     ` David Hildenbrand
2019-11-21  1:07       ` Wei Yang

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