hugetlb: do not fail in hugetlb_cgroup_pre_destroy

Now that pre_destroy callbacks are called from the context where neither
any task can attach the group nor any children group can be added there
is no other way to fail from hugetlb_pre_destroy.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Reviewed-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NGlauber Costa <glommer@parallels.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

mm/hugetlb_cgroup.c

@@ -159,14 +159,9 @@ static int hugetlb_cgroup_pre_destroy(struct cgroup *cgroup)
 {
 	struct hstate *h;
 	struct page *page;
-	int ret = 0, idx = 0;
+	int idx = 0;
 
 	do {
-		if (cgroup_task_count(cgroup) ||
-		    !list_empty(&cgroup->children)) {
-			ret = -EBUSY;
-			goto out;
-		}
 		for_each_hstate(h) {
 			spin_lock(&hugetlb_lock);
 			list_for_each_entry(page, &h->hugepage_activelist, lru)
@@ -177,8 +172,8 @@ static int hugetlb_cgroup_pre_destroy(struct cgroup *cgroup)
 		}
 		cond_resched();
 	} while (hugetlb_cgroup_have_usage(cgroup));
-out:
-	return ret;
+
+	return 0;
 }
 
 int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,