cgroup: remove redundant check in cgroup_ino()

After we implemented default unified hierarchy, cgrp->kn can never
be NULL.
Signed-off-by: NZefan Li <lizefan@huawei.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

include/linux/cgroup.h

@@ -532,13 +532,10 @@ static inline bool cgroup_has_tasks(struct cgroup *cgrp)
 	return !list_empty(&cgrp->cset_links);
 }
 
-/* returns ino associated with a cgroup, 0 indicates unmounted root */
+/* returns ino associated with a cgroup */
 static inline ino_t cgroup_ino(struct cgroup *cgrp)
 {
-	if (cgrp->kn)
-		return cgrp->kn->ino;
-	else
-		return 0;
+	return cgrp->kn->ino;
 }
 
 /* cft/css accessors for cftype->write() operation */

mm/memory-failure.c

@@ -148,7 +148,7 @@ static int hwpoison_filter_task(struct page *p)
 	ino = cgroup_ino(css->cgroup);
 	css_put(css);
 
-	if (!ino || ino != hwpoison_filter_memcg)
+	if (ino != hwpoison_filter_memcg)
 		return -EINVAL;
 
 	return 0;