memory cgroup enhancements: remember "a page is on active list of cgroup or not"

Remember page_cgroup is on active_list or not in page_cgroup->flags.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: David Rientjes <rientjes@google.com>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -86,6 +86,7 @@ struct page_cgroup {
 	int	 flags;
 };
 #define PAGE_CGROUP_FLAG_CACHE	(0x1)	/* charged as cache */
+#define PAGE_CGROUP_FLAG_ACTIVE (0x2)	/* page is active in this cgroup */
 
 enum {
 	MEM_CGROUP_TYPE_UNSPEC = 0,
@@ -213,10 +214,13 @@ clear_page_cgroup(struct page *page, struct page_cgroup *pc)
 
 static void __mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
 {
-	if (active)
+	if (active) {
+		pc->flags |= PAGE_CGROUP_FLAG_ACTIVE;
 		list_move(&pc->lru, &pc->mem_cgroup->active_list);
-	else
+	} else {
+		pc->flags &= ~PAGE_CGROUP_FLAG_ACTIVE;
 		list_move(&pc->lru, &pc->mem_cgroup->inactive_list);
+	}
 }
 
 int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
@@ -403,7 +407,7 @@ retry:
 	atomic_set(&pc->ref_cnt, 1);
 	pc->mem_cgroup = mem;
 	pc->page = page;
-	pc->flags = 0;
+	pc->flags = PAGE_CGROUP_FLAG_ACTIVE;
 	if (ctype == MEM_CGROUP_CHARGE_TYPE_CACHE)
 		pc->flags |= PAGE_CGROUP_FLAG_CACHE;