vmpressure: make sure there are no events queued after memcg is offlined
authorMichal Hocko <mhocko@suse.cz>
Wed, 31 Jul 2013 20:53:51 +0000 (13:53 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 31 Jul 2013 21:41:04 +0000 (14:41 -0700)
commit33cb876e947b9ddda8dca3fb99234b743a597ef9
tree334a94157e6fd53ef9bb88771b181c6cbfa4826a
parent8e0ed445b3478468372449859c45c6b3032acf2f
vmpressure: make sure there are no events queued after memcg is offlined

vmpressure is called synchronously from reclaim where the target_memcg
is guaranteed to be alive but the eventfd is signaled from the work
queue context.  This means that memcg (along with vmpressure structure
which is embedded into it) might go away while the work item is pending
which would result in use-after-release bug.

We have two possible ways how to fix this.  Either vmpressure pins memcg
before it schedules vmpr->work and unpin it in vmpressure_work_fn or
explicitely flush the work item from the css_offline context (as
suggested by Tejun).

This patch implements the later one and it introduces vmpressure_cleanup
which flushes the vmpressure work queue item item.  It hooks into
mem_cgroup_css_offline after the memcg itself is cleaned up.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reported-by: Tejun Heo <tj@kernel.org>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Li Zefan <lizefan@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/vmpressure.h
mm/memcontrol.c
mm/vmpressure.c