linux-kernel - Re: [PATCH 4/4] anonvma: when setting up page->mapping, we need to pick the _oldest

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Date:	Mon, 12 Apr 2010 17:03:16 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Borislav Petkov <bp@...en8.de>,
	Johannes Weiner <hannes@...xchg.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	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
Subject: Re: [PATCH 4/4] anonvma: when setting up page->mapping, we need to
 pick the _oldest_ anonvma

On 04/12/2010 04:23 PM, Linus Torvalds wrote:
>
> From: Linus Torvalds<torvalds@...ux-foundation.org>
> Date: Mon, 12 Apr 2010 12:44:29 -0700
> Subject: [PATCH 4/4] anonvma: when setting up page->mapping, we need to pick the _oldest_ anonvma
>
> Otherwise we might be mapping in a page in a new mapping, but that page
> (through the swapcache) would later be mapped into an old mapping too.
> The page->mapping must be the case that works for everybody, not just
> the mapping that happened to page it in first.
>
> This can be improved in certain cases: if we know the page is private to
> just this particular mapping (for example, it's a new page, or it is the
> only swapcache entry), we could pick the top (most specific) anon_vma.
>
> But that's a future optimization. Make it _work_ reliably first.

Agreed.  I'll send an incremental for that later, you
can judge whether or not it's something you'll want to
merge before or after 2.6.34

> Signed-off-by: Linus Torvalds<torvalds@...ux-foundation.org>

Reviewed-by: Rik van Riel <riel@...hat.com>
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