linux-kernel - Re: [PATCH 10/28] mm: Make use of the anon

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Date:	Wed, 09 Jun 2010 15:32:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Avi Kivity <avi@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Miller <davem@...emloft.net>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Nick Piggin <npiggin@...e.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH 10/28] mm: Make use of the anon_vma ref count

On Wed, 2010-06-09 at 14:22 +0100, Mel Gorman wrote:
> This comment is no longer strictly correct. anon_vma_alloc() can also be
> called from anon_vma_fork where the root of the newly allocated anon_vma
> will be set to the same as the parents anon_vma. Maybe something like
> 
> /*
>  * Initialise the anon_vma root to point to itself. If called from
>  * fork, the root will be reset to the parents anon_vma 
>  */

Sure, I'll change the comment.

> Else, just leave the initialisation of the root where it was but only
> init the refcount here.

Ah, that would lead to problems. We use put_anon_vma() to free in the
create error path, and __put_anon_vma() will also check the
anon_vma->root, so by not setting it the error path will explode.
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