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From: zhong jiang <zhongjiang@huawei.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	Michal Hocko <mhocko@kernel.org>, <akpm@linux-foundation.org>,
	<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: fix account pmd page to the process
Date: Sat, 18 Jun 2016 13:07:55 +0800	[thread overview]
Message-ID: <5764D72B.2080800@huawei.com> (raw)
In-Reply-To: <8141c2df-5643-4ba9-42a5-5b536517cdee@oracle.com>

On 2016/6/17 23:39, Mike Kravetz wrote:
> On 06/17/2016 05:25 AM, Kirill A. Shutemov wrote:
>> From fd22922e7b4664e83653a84331f0a95b985bff0c Mon Sep 17 00:00:00 2001
>> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>> Date: Fri, 17 Jun 2016 15:07:03 +0300
>> Subject: [PATCH] hugetlb: fix nr_pmds accounting with shared page tables
>>
>> We account HugeTLB's shared page table to all processes who share it.
>> The accounting happens during huge_pmd_share().
>>
>> If somebody populates pud entry under us, we should decrease pagetable's
>> refcount and decrease nr_pmds of the process.
>>
>> By mistake, I increase nr_pmds again in this case. :-/
>> It will lead to "BUG: non-zero nr_pmds on freeing mm: 2" on process'
>> exit.
>>
>> Let's fix this by increasing nr_pmds only when we're sure that the page
>> table will be used.
>>
>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Nice,
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
>
> I agree that we do not necessarily need a back port.  I have not seen
> reports of people experiencing this race and seeing the BUG (on mm
> tear-down).
>
> zhongjiang, did someone actually hit the BUG?  Or, did you find it by
> code examination?
>
  just code examination.

WARNING: multiple messages have this Message-ID (diff)
From: zhong jiang <zhongjiang@huawei.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	Michal Hocko <mhocko@kernel.org>,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: fix account pmd page to the process
Date: Sat, 18 Jun 2016 13:07:55 +0800	[thread overview]
Message-ID: <5764D72B.2080800@huawei.com> (raw)
In-Reply-To: <8141c2df-5643-4ba9-42a5-5b536517cdee@oracle.com>

On 2016/6/17 23:39, Mike Kravetz wrote:
> On 06/17/2016 05:25 AM, Kirill A. Shutemov wrote:
>> From fd22922e7b4664e83653a84331f0a95b985bff0c Mon Sep 17 00:00:00 2001
>> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>> Date: Fri, 17 Jun 2016 15:07:03 +0300
>> Subject: [PATCH] hugetlb: fix nr_pmds accounting with shared page tables
>>
>> We account HugeTLB's shared page table to all processes who share it.
>> The accounting happens during huge_pmd_share().
>>
>> If somebody populates pud entry under us, we should decrease pagetable's
>> refcount and decrease nr_pmds of the process.
>>
>> By mistake, I increase nr_pmds again in this case. :-/
>> It will lead to "BUG: non-zero nr_pmds on freeing mm: 2" on process'
>> exit.
>>
>> Let's fix this by increasing nr_pmds only when we're sure that the page
>> table will be used.
>>
>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Nice,
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
>
> I agree that we do not necessarily need a back port.  I have not seen
> reports of people experiencing this race and seeing the BUG (on mm
> tear-down).
>
> zhongjiang, did someone actually hit the BUG?  Or, did you find it by
> code examination?
>
  just code examination.

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  reply	other threads:[~2016-06-18  5:08 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-16 11:36 [PATCH] mm: fix account pmd page to the process zhongjiang
2016-06-16 11:36 ` zhongjiang
2016-06-16 15:42 ` Michal Hocko
2016-06-16 15:42   ` Michal Hocko
2016-06-16 15:43   ` Michal Hocko
2016-06-16 15:43     ` Michal Hocko
2016-06-16 16:05     ` Mike Kravetz
2016-06-16 16:05       ` Mike Kravetz
2016-06-16 16:31       ` Michal Hocko
2016-06-16 16:31         ` Michal Hocko
2016-06-16 16:47         ` Mike Kravetz
2016-06-16 16:47           ` Mike Kravetz
2016-06-17 12:25           ` Kirill A. Shutemov
2016-06-17 12:25             ` Kirill A. Shutemov
2016-06-17 13:00             ` Michal Hocko
2016-06-17 13:00               ` Michal Hocko
2016-06-17 14:25               ` Kirill A. Shutemov
2016-06-17 14:25                 ` Kirill A. Shutemov
2016-06-17 15:39             ` Mike Kravetz
2016-06-17 15:39               ` Mike Kravetz
2016-06-18  5:07               ` zhong jiang [this message]
2016-06-18  5:07                 ` zhong jiang
2016-06-17 11:18   ` zhong jiang
2016-06-17 11:18     ` zhong jiang
     [not found] <1466163941-12952-1-git-send-email-zhongjiang@huawei.com>
2016-06-17 12:01 ` zhong jiang
2016-06-17 12:01   ` zhong jiang
  -- strict thread matches above, loose matches on Subject: below --
2016-06-17 11:56 zhongjiang
2016-06-17 11:56 ` zhongjiang
2016-06-17 12:21 ` Michal Hocko
2016-06-17 12:21   ` Michal Hocko
2016-06-17 13:04   ` zhong jiang
2016-06-17 13:04     ` zhong jiang
     [not found] <1466076175-23444-1-git-send-email-zhongjiang@huawei.com>
2016-06-16 11:30 ` zhong jiang
2016-06-16 11:30   ` zhong jiang
2016-06-16 11:28 zhongjiang
2016-06-16 11:28 ` zhongjiang
2016-06-16 11:17 zhongjiang
2016-06-16 11:17 ` zhongjiang
2016-06-16 11:16 zhongjiang
2016-06-16 11:16 ` zhongjiang
2016-06-16 11:13 zhongjiang
2016-06-16 11:13 ` zhongjiang
2016-06-16  7:47 zhongjiang
2016-06-16  7:47 ` zhongjiang
2016-06-15 14:48 zhongjiang

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