Message-ID: <4BBF8815.7010309@redhat.com>
Date: Fri, 09 Apr 2010 16:03:33 -0400
From: Rik van Riel <riel@redhat.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Borislav Petkov <bp@alien8.de>,
       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,
       hannes@cmpxchg.org
Subject: Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas
 of a mergeable VMA
References: <alpine.LFD.2.00.1004080706500.3586@i5.linux-foundation.org> <20100408210035.GA25834@a1.tnic> <alpine.LFD.2.00.1004081610020.3558@i5.linux-foundation.org> <20100408234721.GB25834@a1.tnic> <alpine.LFD.2.00.1004081744150.3558@i5.linux-foundation.org> <20100409013012.GA8153@liondog.tnic> <20100409092111.GA998@a1.tnic> <alpine.LFD.2.00.1004090917070.3558@i5.linux-foundation.org> <20100409174041.GA10780@a1.tnic> <alpine.LFD.2.00.1004091043490.3558@i5.linux-foundation.org> <20100409191425.GB10780@a1.tnic> <alpine.LFD.2.00.1004091227310.3558@i5.linux-foundation.org>
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On 04/09/2010 03:32 PM, Linus Torvalds wrote:

> Rik? I think it's back to you. I'm not going to bother committing the
> change to the anon_vma locking unless you actually need the locking
> guarantees for anon_vma_prepare().

> And I've got the feeling that the proper fix is in the vma_adjust()
> handling if your original idea was right.

We can fix it on the other side, by changing anon_vma_merge
to actually link all the anon_vma structs into the VMA.

An added benefit is that we are already holding the required
lock (mmap_sem) exclusively in that code path.

I'll cook up a patch and I'll mail it out after a little
testing.
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