cgroup: separate out cgroup_has_live_children() from cgroup_destroy_locked()

We're expecting another user.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b57a949..3f5f481 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3295,6 +3295,21 @@ css_next_descendant_post(struct cgroup_subsys_state *pos,
        return css_parent(pos);
 }
 
+static bool cgroup_has_live_children(struct cgroup *cgrp)
+{
+       struct cgroup *child;
+
+       rcu_read_lock();
+       list_for_each_entry_rcu(child, &cgrp->children, sibling) {
+               if (!cgroup_is_dead(child)) {
+                       rcu_read_unlock();
+                       return true;
+               }
+       }
+       rcu_read_unlock();
+       return false;
+}
+
 /**
  * css_advance_task_iter - advance a task itererator to the next css_set
  * @it: the iterator to advance
@@ -4465,7 +4480,6 @@ static void kill_css(struct cgroup_subsys_state *css)
 static int cgroup_destroy_locked(struct cgroup *cgrp)
        __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
 {
-       struct cgroup *child;
        struct cgroup_subsys_state *css;
        bool empty;
        int ssid;
@@ -4487,15 +4501,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
         * emptiness as dead children linger on it while being destroyed;
         * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
         */
-       empty = true;
-       rcu_read_lock();
-       list_for_each_entry_rcu(child, &cgrp->children, sibling) {
-               empty = cgroup_is_dead(child);
-               if (!empty)
-                       break;
-       }
-       rcu_read_unlock();
-       if (!empty)
+       if (cgroup_has_live_children(cgrp))
                return -EBUSY;
 
        /*