4 files changed, 51 insertions, 0 deletions
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index dddedfc0af8..16b28647304 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -152,6 +152,7 @@ enum rq_flag_bits {
 	__REQ_IO_STAT,		/* account I/O stat */
 	__REQ_MIXED_MERGE,	/* merge of different types, fail separately */
 	__REQ_SECURE,		/* secure discard (used with __REQ_DISCARD) */
+	__REQ_ON_PLUG,		/* on plug list */
 	__REQ_NR_BITS,		/* stops here */
 };
 
@@ -193,5 +194,6 @@ enum rq_flag_bits {
 #define REQ_IO_STAT		(1 << __REQ_IO_STAT)
 #define REQ_MIXED_MERGE		(1 << __REQ_MIXED_MERGE)
 #define REQ_SECURE		(1 << __REQ_SECURE)
+#define REQ_ON_PLUG		(1 << __REQ_ON_PLUG)
 
 #endif /* __LINUX_BLK_TYPES_H */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f55b2a8b661..5873037eeb9 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -871,6 +871,31 @@ 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 *);
 
+struct blk_plug {
+	unsigned long magic;
+	struct list_head list;
+	unsigned int should_sort;
+};
+
+extern void blk_start_plug(struct blk_plug *);
+extern void blk_finish_plug(struct blk_plug *);
+extern void __blk_flush_plug(struct task_struct *, struct blk_plug *);
+
+static inline void blk_flush_plug(struct task_struct *tsk)
+{
+	struct blk_plug *plug = tsk->plug;
+
+	if (unlikely(plug))
+		__blk_flush_plug(tsk, plug);
+}
+
+static inline bool blk_needs_flush_plug(struct task_struct *tsk)
+{
+	struct blk_plug *plug = tsk->plug;
+
+	return plug && !list_empty(&plug->list);
+}
+
 /*
  * tag stuff
  */
@@ -1294,6 +1319,23 @@ static inline long nr_blockdev_pages(void)
 	return 0;
 }
 
+static inline void blk_start_plug(struct list_head *list)
+{
+}
+
+static inline void blk_finish_plug(struct list_head *list)
+{
+}
+
+static inline void blk_flush_plug(struct task_struct *tsk)
+{
+}
+
+static inline bool blk_needs_flush_plug(struct task_struct *tsk)
+{
+	return false;
+}
+
 #endif /* CONFIG_BLOCK */
 
 #endif
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 39b68edb388..8857cf9adbb 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -105,6 +105,7 @@ extern void elv_add_request(struct request_queue *, struct request *, int, int);
 extern void __elv_add_request(struct request_queue *, struct request *, int, int);
 extern void elv_insert(struct request_queue *, struct request *, int);
 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
+extern int elv_try_merge(struct request *, struct bio *);
 extern void elv_merge_requests(struct request_queue *, struct request *,
 			       struct request *);
 extern void elv_merged_request(struct request_queue *, struct request *, int);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 777d8a5ed06..96ac2264374 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -99,6 +99,7 @@ struct robust_list_head;
 struct bio_list;
 struct fs_struct;
 struct perf_event_context;
+struct blk_plug;
 
 /*
  * List of flags we want to share for kernel threads,
@@ -1429,6 +1430,11 @@ struct task_struct {
 /* stacked block device info */
 	struct bio_list *bio_list;
 
+#ifdef CONFIG_BLOCK
+/* stack plugging */
+	struct blk_plug *plug;
+#endif
+
 /* VM state */
 	struct reclaim_state *reclaim_state;