diff --git a/[refs] b/[refs]
index bb5852a83860..ac0d524985b7 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5a042aa4b8e994a15d2c2ee750219971f0ab3905
+refs/heads/master: 09f40f98bfa2ac22a332a713629a2f8f92896834
diff --git a/trunk/mm/backing-dev.c b/trunk/mm/backing-dev.c
index 94a047bb6c39..a87da524a4a0 100644
--- a/trunk/mm/backing-dev.c
+++ b/trunk/mm/backing-dev.c
@@ -401,6 +401,13 @@ static int bdi_forker_thread(void *ptr)
 		}
 
 		spin_lock_bh(&bdi_lock);
+		/*
+		 * In the following loop we are going to check whether we have
+		 * some work to do without any synchronization with tasks
+		 * waking us up to do work for them. So we have to set task
+		 * state already here so that we don't miss wakeups coming
+		 * after we verify some condition.
+		 */
 		set_current_state(TASK_INTERRUPTIBLE);
 
 		list_for_each_entry(bdi, &bdi_list, bdi_list) {