cgroup: implement cgroup_from_id()

[platform/adaptation/renesas_rcar/renesas_kernel.git] / include / linux / cgroup.h

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 4dfcd0e..bbf4d89 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -720,6 +720,24 @@ static inline struct cgroup* task_cgroup(struct task_struct *task,
        return task_subsys_state(task, subsys_id)->cgroup;
 }
 
+/**
+ * cgroup_from_id - lookup cgroup by id
+ * @ss: cgroup subsys to be looked into
+ * @id: the cgroup id
+ *
+ * Returns the cgroup if there's valid one with @id, otherwise returns NULL.
+ * Should be called under rcu_read_lock().
+ */
+static inline struct cgroup *cgroup_from_id(struct cgroup_subsys *ss, int id)
+{
+#ifdef CONFIG_PROVE_RCU
+       rcu_lockdep_assert(rcu_read_lock_held() ||
+                          lockdep_is_held(&cgroup_mutex),
+                          "cgroup_from_id() needs proper protection");
+#endif
+       return idr_find(&ss->root->cgroup_idr, id);
+}
+
 struct cgroup *cgroup_next_sibling(struct cgroup *pos);
 
 /**