Subject: Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the
 anon_vmas of a mergeable VMA
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@redhat.com>, Borislav Petkov <bp@alien8.de>,
       Johannes Weiner <hannes@cmpxchg.org>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Minchan Kim <minchan.kim@gmail.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
       Nick Piggin <npiggin@suse.de>, Andrea Arcangeli <aarcange@redhat.com>,
       Hugh Dickins <hugh.dickins@tiscali.co.uk>, sgunderson@bigfoot.com
In-Reply-To: <1271100621.20295.3397.camel@laptop>
References: <20100409191425.GB10780@a1.tnic>
	 <alpine.LFD.2.00.1004091227310.3558@i5.linux-foundation.org>
	 <20100409204328.GG28964@cmpxchg.org>
	 <alpine.LFD.2.00.1004091546350.3558@i5.linux-foundation.org>
	 <alpine.LFD.2.00.1004091638290.3558@i5.linux-foundation.org>
	 <20100410003110.GI28964@cmpxchg.org>
	 <alpine.LFD.2.00.1004091730130.3558@i5.linux-foundation.org>
	 <20100410072714.GA9246@liondog.tnic> <20100410112639.GA24708@a1.tnic>
	 <alpine.LFD.2.00.1004100821340.3558@i5.linux-foundation.org>
	 <20100410163828.GA25579@a1.tnic>
	 <alpine.LFD.2.00.1004100947400.3558@i5.linux-foundation.org>
	 <alpine.LFD.2.00.1004101101180.3558@i5.linux-foundation.org>
	 <1271083207.4807.18.camel@twins>  <4BC33A02.8000307@redhat.com>
	 <1271088103.20295.3383.camel@laptop> <4BC34501.5060401@redhat.com>
	 <alpine.LFD.2.00.1004120941310.26679@i5.linux-foundation.org>
	 <1271097638.4807.129.camel@twins>  <1271100621.20295.3397.camel@laptop>
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Date: Mon, 12 Apr 2010 21:44:34 +0200
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On Mon, 2010-04-12 at 21:30 +0200, Peter Zijlstra wrote:
> 
> We could here return a non-valid and already freed anon_vma.
> 
OK, so non of the users of page_lock_anon_vma() with exception of the
memory-failure.c one could really care. And all of them seem to be safe
enough wrt dealing with a dead one.

So unless people care, I'm going to not spend more time on trying to
make page_lock_anon_vma() behave.

Instead I'll try and see wth it is that migrate.c and rmap_walk_anon are
doing.

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