tree e6ed4f1c3b98474996b6b61e232569564d86d352
parent 4a4389abdd9822fdf3cc2ac6ed87eb811fd43acc
author Li Zefan <lizefan@huawei.com> 1396602881 +0800
committer Tejun Heo <tj@kernel.org> 1396614147 -0400

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>