From: Mel Gorman <mel@csn.ul.ie>
Date: Tue, 15 Dec 2009 01:59:53 +0000 (-0800)
Subject: hugetlb: acquire the i_mmap_lock before walking the prio_tree to unmap a page
X-Git-Tag: v2.6.33-rc1~185
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4eb2b1dcd598f8489130405c81c60c289896d92a;p=pandora-kernel.git

hugetlb: acquire the i_mmap_lock before walking the prio_tree to unmap a page

When the owner of a mapping fails COW because a child process is holding a
reference, the children VMAs are walked and the page is unmapped.  The
i_mmap_lock is taken for the unmapping of the page but not the walking of
the prio_tree.  In theory, that tree could be changing if the lock is not
held.  This patch takes the i_mmap_lock properly for the duration of the
prio_tree walk.

[hugh.dickins@tiscali.co.uk: Spotted the problem in the first place]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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