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-rw-r--r--include/linux/cgroup.h30
1 files changed, 30 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c9fdf6f57913..32c553556bbd 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -554,6 +554,36 @@ static inline bool cgroup_is_descendant(struct cgroup *cgrp,
}
/**
+ * cgroup_ancestor - find ancestor of cgroup
+ * @cgrp: cgroup to find ancestor of
+ * @ancestor_level: level of ancestor to find starting from root
+ *
+ * Find ancestor of cgroup at specified level starting from root if it exists
+ * and return pointer to it. Return NULL if @cgrp doesn't have ancestor at
+ * @ancestor_level.
+ *
+ * This function is safe to call as long as @cgrp is accessible.
+ */
+static inline struct cgroup *cgroup_ancestor(struct cgroup *cgrp,
+ int ancestor_level)
+{
+ struct cgroup *ptr;
+
+ if (cgrp->level < ancestor_level)
+ return NULL;
+
+ for (ptr = cgrp;
+ ptr && ptr->level > ancestor_level;
+ ptr = cgroup_parent(ptr))
+ ;
+
+ if (ptr && ptr->level == ancestor_level)
+ return ptr;
+
+ return NULL;
+}
+
+/**
* task_under_cgroup_hierarchy - test task's membership of cgroup ancestry
* @task: the task to be tested
* @ancestor: possible ancestor of @task's cgroup