diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index f952a07..60e9587 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -42,6 +42,7 @@
 	MEM_CGROUP_STAT_RSS,		/* # of pages charged as anon rss */
 	MEM_CGROUP_STAT_RSS_HUGE,	/* # of pages charged as anon huge */
 	MEM_CGROUP_STAT_FILE_MAPPED,	/* # of pages charged as file rss */
+	MEM_CGROUP_STAT_WRITEBACK,	/* # of pages under writeback */
 	MEM_CGROUP_STAT_SWAP,		/* # of pages, swapped out */
 	MEM_CGROUP_STAT_NSTATS,
 };