memcg: remove redundant code in mem_cgroup_force_empty_write()

vfs guarantees the cgroup won't be destroyed, so it's redundant to get a
css reference.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c6bd28e..fe6b9f9 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4990,18 +4990,12 @@ static int mem_cgroup_force_empty_write(struct cgroup_subsys_state *css,
                                        unsigned int event)
 {
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
-       int ret;
 
        if (mem_cgroup_is_root(memcg))
                return -EINVAL;
-       css_get(&memcg->css);
-       ret = mem_cgroup_force_empty(memcg);
-       css_put(&memcg->css);
-
-       return ret;
+       return mem_cgroup_force_empty(memcg);
 }
 
-
 static u64 mem_cgroup_hierarchy_read(struct cgroup_subsys_state *css,
                                     struct cftype *cft)
 {