linux-kernel - Re: [PATCH 0/6] mempolicy memory corruption fixlet

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Message-ID: <4FC69035.3000509@gmail.com>
Date:	Wed, 30 May 2012 17:25:09 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Ben Hutchings <ben@...adent.org.uk>
CC:	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Lameter <cl@...ux.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...gle.com>, Dave Jones <davej@...hat.com>,
	Mel Gorman <mgorman@...e.de>, stable@...r.kernel.org,
	hughd@...gle.com, sivanich@....com
Subject: Re: [PATCH 0/6] mempolicy memory corruption fixlet

(5/30/12 5:22 PM), Ben Hutchings wrote:
> On Wed, May 30, 2012 at 04:00:55PM -0400, KOSAKI Motohiro wrote:
>> On Wed, May 30, 2012 at 3:52 PM, Andi Kleen<andi@...stfloor.org>  wrote:
>>> On Wed, May 30, 2012 at 02:42:42PM -0500, Christoph Lameter wrote:
>>>> On Wed, 30 May 2012, Andi Kleen wrote:
>>>>
>>>>> On Wed, May 30, 2012 at 01:50:02PM -0500, Christoph Lameter wrote:
>>>>>> On Wed, 30 May 2012, Andi Kleen wrote:
>>>>>>
>>>>>>> I always regretted that cpusets were no done with custom node lists.
>>>>>>> That would have been much cleaner and also likely faster than what we have.
>>>>>>
>>>>>> Could shared memory policies ignore cpuset constraints?
>>>>>
>>>>> Only if noone uses cpusets as a "security" mechanism, just for a "soft policy"
>>>>> Even with soft policy you could well break someone's setup.
>>>>
>>>> Well at least lets exempt shared memory from memory migration and memory
>>>> policy updates. That seems to be causing many of these issues.
>>>
>>> Migration on the page level is needed for the memory error handling.
>>>
>>> Updates: you mean not allowing to set the policy when there are already
>>> multiple mappers? I could see that causing some unexpected behaviour. Presumably
>>> a standard database will only set it at the beginning, but I don't know
>>> if that would work for all users.
>>
>> We don't need to kill migration core. We only need to kill that mbind(2) updates
>> vma->policy of shmem.
> [...]
>
> So should I (and Greg) drop 'mm: mempolicy: Let vma_merge and
> vma_split handle vma->vm_policy linkages' from the pending stable
> releases?  Or is that OK as an interim fix until these changes go
> into mainline?

Please drop. It screw up mbind(2).




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