linux-imx

cgroup: avoid copying strings longer than the buffers

cgroup root name and file name have max length limit, we should
avoid copying longer name than that to the name.

tj: minor update to $SUBJ.

Signed-off-by: Ma Shimiao <mashimiao.fnst@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>