---

yaml
---
r: 110555
b: refs/heads/master
c: ef9e3fa
h: refs/heads/master
i:
  110553: 9c857d7
  110551: 86e5770
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 336c3d8ce771608815b65bcfa27a17a83b297328
+refs/heads/master: ef9e3facdf1fe1228721a7c295a76d1b7a0e57ec

trunk/block/blk-core.c

@@ -2100,6 +2100,34 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
 		rq->rq_disk = bio->bi_bdev->bd_disk;
 }
 
+/**
+ * blk_lld_busy - Check if underlying low-level drivers of a device are busy
+ * @q : the queue of the device being checked
+ *
+ * Description:
+ *    Check if underlying low-level drivers of a device are busy.
+ *    If the drivers want to export their busy state, they must set own
+ *    exporting function using blk_queue_lld_busy() first.
+ *
+ *    Basically, this function is used only by request stacking drivers
+ *    to stop dispatching requests to underlying devices when underlying
+ *    devices are busy.  This behavior helps more I/O merging on the queue
+ *    of the request stacking driver and prevents I/O throughput regression
+ *    on burst I/O load.
+ *
+ * Return:
+ *    0 - Not busy (The request stacking driver should dispatch request)
+ *    1 - Busy (The request stacking driver should stop dispatching request)
+ */
+int blk_lld_busy(struct request_queue *q)
+{
+	if (q->lld_busy_fn)
+		return q->lld_busy_fn(q);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(blk_lld_busy);
+
 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
 {
 	return queue_work(kblockd_workqueue, work);

trunk/block/blk-settings.c

@@ -89,6 +89,12 @@ void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
 }
 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
 
+void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
+{
+	q->lld_busy_fn = fn;
+}
+EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
+
 /**
  * blk_queue_make_request - define an alternate make_request function for a device
  * @q:  the request queue for the device to be affected

trunk/include/linux/blkdev.h

@@ -269,6 +269,7 @@ typedef int (merge_bvec_fn) (struct request_queue *, struct bvec_merge_data *,
 typedef void (prepare_flush_fn) (struct request_queue *, struct request *);
 typedef void (softirq_done_fn)(struct request *);
 typedef int (dma_drain_needed_fn)(struct request *);
+typedef int (lld_busy_fn) (struct request_queue *q);
 
 enum blk_eh_timer_return {
 	BLK_EH_NOT_HANDLED,
@@ -325,6 +326,7 @@ struct request_queue
 	softirq_done_fn		*softirq_done_fn;
 	rq_timed_out_fn		*rq_timed_out_fn;
 	dma_drain_needed_fn	*dma_drain_needed;
+	lld_busy_fn		*lld_busy_fn;
 
 	/*
 	 * Dispatch queue sorting
@@ -699,6 +701,7 @@ extern struct request *blk_get_request(struct request_queue *, int, gfp_t);
 extern void blk_insert_request(struct request_queue *, struct request *, int, void *);
 extern void blk_requeue_request(struct request_queue *, struct request *);
 extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);
+extern int blk_lld_busy(struct request_queue *q);
 extern int blk_insert_cloned_request(struct request_queue *q,
 				     struct request *rq);
 extern void blk_plug_device(struct request_queue *);
@@ -835,6 +838,7 @@ extern void blk_queue_update_dma_pad(struct request_queue *, unsigned int);
 extern int blk_queue_dma_drain(struct request_queue *q,
 			       dma_drain_needed_fn *dma_drain_needed,
 			       void *buf, unsigned int size);
+extern void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn);
 extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
 extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
 extern void blk_queue_merge_bvec(struct request_queue *, merge_bvec_fn *);