+ * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
+ * @task: target task
+ * @buf: the buffer to write the path into
+ * @buflen: the length of the buffer
+ *
+ * Determine @task's cgroup on the first (the one with the lowest non-zero
+ * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
+ * function grabs cgroup_mutex and shouldn't be used inside locks used by
+ * cgroup controller callbacks.
+ *
+ * Return value is the same as kernfs_path().
+ */
+int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
+{
+ struct cgroup_root *root;
+ struct cgroup *cgrp;
+ int hierarchy_id = 1;
+ int ret;
+
+ cgroup_lock();
+ spin_lock_irq(&css_set_lock);
+
+ root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
+
+ if (root) {
+ cgrp = task_cgroup_from_root(task, root);
+ ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
+ } else {
+ /* if no hierarchy exists, everyone is in "/" */
+ ret = strscpy(buf, "/", buflen);
+ }
+
+ spin_unlock_irq(&css_set_lock);
+ cgroup_unlock();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(task_cgroup_path);
+
+/**