linux-kernel - [PATCH 0/2] page munlock issues when breaking up COW

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Date:	Mon,  7 Feb 2011 16:47:34 -0800
From:	Michel Lespinasse <walken@...gle.com>
To:	linux-mm@...ck.org, Lee Schermerhorn <lee.schermerhorn@...com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] page munlock issues when breaking up COW

It looks like there is a race in the do_wp_page() code that munlocks the
old page after breaking up COW. The pte still points to that old page,
so I don't see that we are protected against vmscan mlocking back the
page right away. This can be easily worked around by moving that code to
the end of do_wp_page(), after the pte has been pointed to the new page.

Also, the corresponding code in __do_fault() seems entirely unnecessary,
since there was never a pte pointing to the old page in our vma.

Michel Lespinasse (2):
  mlock: fix race when munlocking pages in do_wp_page()
  mlock: do not munlock pages in __do_fault()

 mm/memory.c |   32 ++++++++++++--------------------
 1 files changed, 12 insertions(+), 20 deletions(-)

-- 
1.7.3.1
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