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authorHugh Dickins <hugh@veritas.com>2008-03-04 14:29:13 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-04 16:35:15 -0800
commit2680eed723b664d83e6181ae275fac0ec8fa05ff (patch)
treef4c137e43c3bdf78e6923bb3aafaf38680c4c301 /mm/memory.c
parent6d48ff8bcfd403ec8d3ef7a56538ea9e6f773b9c (diff)
downloadop-kernel-dev-2680eed723b664d83e6181ae275fac0ec8fa05ff.zip
op-kernel-dev-2680eed723b664d83e6181ae275fac0ec8fa05ff.tar.gz
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 <hugh@veritas.com> Cc: David Rientjes <rientjes@google.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hirokazu Takahashi <taka@valinux.co.jp> Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp> Cc: Paul Menage <menage@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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