diff --git a/[refs] b/[refs]
index 702a49954eb5..012b963725d0 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 55c022bbddb2c056b5dff1bd1b1758d31b6d64c9
+refs/heads/master: 316cc67d5e03801a5ee4ac660a4dfe9e02aed475
diff --git a/trunk/include/linux/blkdev.h b/trunk/include/linux/blkdev.h
index 92edb9601242..6dcea6885a5d 100644
--- a/trunk/include/linux/blkdev.h
+++ b/trunk/include/linux/blkdev.h
@@ -857,6 +857,12 @@ struct request_queue *blk_alloc_queue(gfp_t);
 struct request_queue *blk_alloc_queue_node(gfp_t, int);
 extern void blk_put_queue(struct request_queue *);
 
+/*
+ * Note: Code in between changing the blk_plug list/cb_list or element of such
+ * lists is preemptable, but such code can't do sleep (or be very careful),
+ * otherwise data is corrupted. For details, please check schedule() where
+ * blk_schedule_flush_plug() is called.
+ */
 struct blk_plug {
 	unsigned long magic;
 	struct list_head list;