cgroup: Remove unnecessary list_empty()

The root hasn't been removed from the root_list, so the list can't be NULL.
However, if it had been removed, attempting to destroy it once more is not
possible. Let's replace this with WARN_ON_ONCE() for clarity.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 1d5b9de3b1b9d01791b1222bf2fcbb4e46c852ee..3a436e4f0da18a3259943f64fc7208020d7ba477 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1347,10 +1347,9 @@ static void cgroup_destroy_root(struct cgroup_root *root)
 
        spin_unlock_irq(&css_set_lock);
 
-       if (!list_empty(&root->root_list)) {
-               list_del(&root->root_list);
-               cgroup_root_count--;
-       }
+       WARN_ON_ONCE(list_empty(&root->root_list));
+       list_del(&root->root_list);
+       cgroup_root_count--;
 
        if (!have_favordynmods)
                cgroup_favor_dynmods(root, false);