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

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Message-ID: <516D4D08.9020602@linux.vnet.ibm.com>
Date:	Tue, 16 Apr 2013 21:07:20 +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 04/16/2013 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.

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