linux-kernel - Re: [PATCH] mm: mmu_notifier: re-fix freed page still mapped in secondary MMU

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Date:	Wed, 17 Apr 2013 10:55:26 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Robin Holt <holt@....com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Avi Kivity <avi.kivity@...il.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: mmu_notifier: re-fix freed page still mapped in secondary
 MMU

On 04/17/2013 02:08 AM, Robin Holt wrote:
> On Tue, Apr 16, 2013 at 09:07:20PM +0800, Xiao Guangrong wrote:
>> On 04/16/2013 07:43 PM, Robin Holt wrote:
>>> Argh.  Taking a step back helped clear my head.
>>>
>>> For the -stable releases, I agree we should just go with your
>>> revert-plus-hlist_del_init_rcu patch.  I will give it a test
>>> when I am in the office.
>>
>> Okay. Wait for your test report. Thank you in advance.
>>
>>>
>>> For the v3.10 release, we should work on making this more
>>> correct and completely documented.
>>
>> Better document is always welcomed.
>>
>> Double call ->release is not bad, like i mentioned it in the changelog:
>>
>> it is really rare (e.g, can not happen on kvm since mmu-notify is unregistered
>> after exit_mmap()) and the later call of multiple ->release should be
>> fast since all the pages have already been released by the first call.
>>
>> But, of course, it's great if you have a _light_ way to avoid this.
> 
> Getting my test environment set back up took longer than I would have liked.
> 
> Your patch passed.  I got no NULL-pointer derefs.

Thanks for your test again.

> 
> How would you feel about adding the following to your patch?

I prefer to make these changes as a separate patch, this change is the
improvement, please do not mix it with bugfix.

You can make a patchset (comments improvement and this change) based on
my fix.


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