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authorLi Zefan <lizefan@huawei.com>2013-07-31 09:51:31 +0800
committerTejun Heo <tj@kernel.org>2013-07-31 07:47:34 -0400
commite14880f7bb7e0dc0933af304998371dd543ceb40 (patch)
treed17af9f967acdce1761264a2361986f10348995e
parentb414dc09a31d41d696093a4cce9fb2853a5ecd4e (diff)
downloadlinux-e14880f7bb7e0dc0933af304998371dd543ceb40.tar.bz2
cgroup: implement cgroup_from_id()
This will be used as a replacement for css_lookup(). There's a difference with cgroup id and css id. cgroup id starts with 0, while css id starts with 1. v4: - also check if cggroup_mutex is held. - make it an inline function. Signed-off-by: Li Zefan <lizefan@huawei.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--include/linux/cgroup.h18
1 files changed, 18 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 4dfcd0e1b73e..bbf4d89b56a8 100644
--- 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);
/**