[PATCH 3/8] cgroup: use cgroup_lock_live_group(parent) in cgroup_create()

[Li Zefan]

On 2012/11/1 3:44, Tejun Heo wrote:
> This patch makes cgroup_create() fail if @parent is marked removed.
> This is to prepare for further updates to cgroup_rmdir() path.
> 
> Note that this change isn't strictly necessary.  cgroup can only be
> created via mkdir and the removed marking and dentry removal happen
> without releasing cgroup_mutex, so cgroup_create() can never race with
> cgroup_rmdir().  Even after the scheduled updates to cgroup_rmdir(),
> cgroup_mkdir() and cgroup_rmdir() are synchronized by i_mutex
> rendering the added liveliness check unnecessary.
> 
> Do it anyway such that locking is contained inside cgroup proper and
> we don't get nasty surprises if we ever grow another caller of
> cgroup_create().
> 
> Signed-off-by: Tejun Heo <tj at kernel.org>
> Reviewed-by: Michal Hocko <mhocko at suse.cz>

Acked-by: Li Zefan <lizefan at huawei.com>