cgroups: add 'data' field to struct cgroup_scanner

We need to pass some data to test_task() or process_task() in some cases.
Will be used later.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/cgroup.h

@@ -337,6 +337,7 @@ struct cgroup_scanner {
 	void (*process_task)(struct task_struct *p,
 			struct cgroup_scanner *scan);
 	struct ptr_heap *heap;
+	void *data;
 };
 
 /*