linux-kernel - Re: [PATCH 3/3] Fix unsuitable behavior for poisoned tail pages of THP.

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Date:	Thu, 27 Jan 2011 09:13:52 +0900
From:	Jin Dongming <jin.dongming@...css.fujitsu.com>
To:	Andrea Arcangeli <aarcange@...hat.com>
CC:	Andi Kleen <andi@...stfloor.org>,
	AKPM　 <akpm@...ux-foundation.org>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Huang Ying <ying.huang@...el.com>,
	LKLM <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] Fix unsuitable behavior for poisoned tail pages of
 THP.

Hi, Andrea
(2011/01/26 7:46), Andrea Arcangeli wrote:
> On Tue, Jan 25, 2011 at 02:46:32PM +0900, Jin Dongming wrote:
>> When a tail page of THP is poisoned, memory-failure will do
>> nothing except setting poison flag, while the expected behavior is
>> that the process, who is using the poisoned tail page, should be
>> killed.
>>
>> The above problem is caused by lru checking of the poisoned tail page
>> of THP. Because PG_lru flag is only set on the head page of
>> THP, the check always consider the poisoned tail page as NON
>> lru page.
>>
>> So avoid checking NON lru for THP, as like as hugetlb.
>>
>> Signed-off-by: Jin Dongming <jin.dongming@...css.fujitsu.com>
>> Reviewed-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
>> ---
>>  mm/memory-failure.c |   27 +++++++++++++++------------
>>  1 files changed, 15 insertions(+), 12 deletions(-)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 5396603..44a1bdf 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -1046,19 +1046,22 @@ int __memory_failure(unsigned long pfn, int trapno, int flags)
>>  	 * The check (unnecessarily) ignores LRU pages being isolated and
>>  	 * walked by the page reclaim code, however that's not a big loss.
>>  	 */
>> -	if (!PageLRU(p) && !PageHuge(p))
>> -		shake_page(p, 0);
>> -	if (!PageLRU(p) && !PageHuge(p)) {
>> -		/*
>> -		 * shake_page could have turned it free.
>> -		 */
>> -		if (is_free_buddy_page(p)) {
>> -			action_result(pfn, "free buddy, 2nd try", DELAYED);
>> -			return 0;
>> +	if (!PageCompound(p)) {
> 
> Here the check could become a:
> 
>         if (!PageHuge(p) && !PageTransCompound(p))
> 
I will modify it.

Thanks.

Best Regards,
Jin Dongming

> so the whole branch is optimized away at build time when both
> hugetlbfs and THP are set =n (or in archs not supporting either of
> those).
> 
> --
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