From: Li Zefan <lizefan@huawei.com>
Date: Fri, 4 Apr 2014 09:14:41 +0000 (+0800)
Subject: cgroup: fix top cgroup refcnt leak
X-Git-Tag: v3.15-rc1~58^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c6b3d5bcd67c75961a1e8b9564d1475c0f194a84;p=pandora-kernel.git

cgroup: fix top cgroup refcnt leak

As mount() and kill_sb() is not a one-to-one match, If we mount the same
cgroupfs in serveral mount points, and then umount all of them, kill_sb()
will be called only once.

Try:
        # mount -t cgroup -o cpuacct xxx /cgroup
        # mount -t cgroup -o cpuacct xxx /cgroup2
        # cat /proc/cgroups | grep cpuacct
        cpuacct 2       1       1
        # umount /cgroup
        # umount /cgroup2
        # cat /proc/cgroups | grep cpuacct
        cpuacct 2       1       1

You'll see cgroupfs will never be freed.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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