Date: Mon, 12 Apr 2010 08:44:08 -0700 (PDT)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Rik van Riel <riel@redhat.com>
cc: 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
Subject: Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas
 of a mergeable VMA
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On Sun, 11 Apr 2010, Rik van Riel wrote:
> 
> Looking around the code some more, zap_pte_range()
> calls page_remove_rmap(), which leaves the
> page->mapping in place and has this comment:

See my earlier email about this exact issue. It's well-known that there 
are stale page->mapping pointers. The "page_mapped()" check _should_ have 
meant that in that case we never follow them, though.

> I wonder if we can clear page->mapping here, if
> list_is_singular(anon_vma->head).  That way we
> will not leave stale pointers behind.

What does that help? What if list _isn't_ singular?

		Linus
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