From: Hugh Dickins Date: Tue, 4 Mar 2008 22:29:13 +0000 (-0800) Subject: memcg: fix mem_cgroup_move_lists locking X-Git-Tag: v2.6.25-rc4~36 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2680eed723b664d83e6181ae275fac0ec8fa05ff;p=pandora-kernel.git memcg: fix mem_cgroup_move_lists locking Ever since the VM_BUG_ON(page_get_page_cgroup(page)) (now Bad page state) went into page freeing, I've hit it from time to time in testing on some machines, sometimes only after many days. Recently found a machine which could usually produce it within a few hours, which got me there at last. The culprit is mem_cgroup_move_lists, whose locking is inadequate; and the arrangement of structures was such that you got page_cgroups from the lru list neatly put on to SLUB's freelist. Kamezawa-san identified the same hole independently. The main problem was that it was missing the lock_page_cgroup it needs to safely page_get_page_cgroup; but it's tricky to go beyond that too, and I couldn't do it with SLAB_DESTROY_BY_RCU as I'd expected. See the code for comments on the constraints. This patch immediately gets replaced by a simpler one from Hirokazu-san; but is it just foolish pride that tells me to put this one on record, in case we need to come back to it later? Signed-off-by: Hugh Dickins Cc: David Rientjes Cc: Balbir Singh Acked-by: KAMEZAWA Hiroyuki Cc: Hirokazu Takahashi Cc: YAMAMOTO Takashi Cc: Paul Menage Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed