From: Li Zefan <lizefan@huawei.com>
Date: Tue, 9 Apr 2013 02:00:38 +0000 (-0700)
Subject: cgroup: implement cgroup_is_descendant()
X-Git-Tag: omap-for-v3.10/dt-fixes-for-merge-window~124^2~15
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=78574cf981cd3d9ae9f6adbd466a772310ec24ff;p=pandora-kernel.git

cgroup: implement cgroup_is_descendant()

A couple controllers want to determine whether two cgroups are in
ancestor/descendant relationship.  As it's more likely that the
descendant is the primary subject of interest and there are other
operations focusing on the descendants, let's ask is_descendent rather
than is_ancestor.

Implementation is trivial as the previous patch guarantees that all
ancestors of a cgroup stay accessible as long as the cgroup is
accessible.

tj: Removed depth optimization, renamed from cgroup_is_ancestor(),
    rewrote descriptions.

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