linux-kernel - Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon

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Message-ID: <alpine.LFD.2.00.1004071510080.3586@i5.linux-foundation.org>
Date:	Wed, 7 Apr 2010 15:15:21 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Rik van Riel <riel@...hat.com>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	sgunderson@...foot.com, hannes@...xchg.org
Subject: Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas
 of a mergeable VMA



On Wed, 7 Apr 2010, Linus Torvalds wrote:
> 
> In the long run, it would be nicer to actually return an error from the 
> mmap() that fails, but that's more complicated, and as mentioned, it's not 
> what the old code used to do either (since the failure point was always at 
> the page fault stage).

Put another way: I'm not proud of it, but the new code isn't any worse 
than what we used to have, and I think the new code is _fixable_.

The easiest way to do that would likely be to pre-allocate the anon_vma 
struct (and anon_vma_chain), and pass it down to anon_vma_prepare. That 
way anon_vma_prepare() itself can never fail, and all we need to do is a 
simple allocation earlier in the call-chain.

			Linus
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