From f169007b2773f285e098cb84c74aac0154d65ff7 Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan@huawei.com>
Date: Mon, 18 Feb 2013 14:13:35 +0800
Subject: [PATCH] cgroup: fail if monitored file and event_control are in
 different cgroup

If we pass fd of memory.usage_in_bytes of cgroup A to cgroup.event_control
of cgroup B, then we won't get memory usage notification from A but B!

What's worse, if A and B are in different mount hierarchy, we'll end up
accessing NULL pointer!

Disallow this kind of invalid usage.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Reading git-format-patch failed