Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block

* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  block: only force kblockd unplugging from the schedule() path
  block: cleanup the block plug helper functions
  block, blk-sysfs: Use the variable directly instead of a function call
  block: move queue run on unplug to kblockd
  block: kill queue_sync_plugs()
  block: readd plug trace event
  block: add callback function for unplug notification
  block: add comment on why we save and disable interrupts in flush_plug_list()
  block: fixup block IO unplug trace call
  block: remove block_unplug_timer() trace point
  block: splice plug list to local context

block/blk-core.c

@@ -198,19 +198,6 @@ void blk_dump_rq_flags(struct request *rq, char *msg)
 }
 EXPORT_SYMBOL(blk_dump_rq_flags);
 
-/*
- * Make sure that plugs that were pending when this function was entered,
- * are now complete and requests pushed to the queue.
-*/
-static inline void queue_sync_plugs(struct request_queue *q)
-{
-	/*
-	 * If the current process is plugged and has barriers submitted,
-	 * we will livelock if we don't unplug first.
-	 */
-	blk_flush_plug(current);
-}
-
 static void blk_delay_work(struct work_struct *work)
 {
 	struct request_queue *q;
@@ -298,7 +285,6 @@ void blk_sync_queue(struct request_queue *q)
 {
 	del_timer_sync(&q->timeout);
 	cancel_delayed_work_sync(&q->delay_work);
-	queue_sync_plugs(q);
 }
 EXPORT_SYMBOL(blk_sync_queue);
 
@@ -1311,7 +1297,15 @@ static int __make_request(struct request_queue *q, struct bio *bio)
 
 	plug = current->plug;
 	if (plug) {
-		if (!plug->should_sort && !list_empty(&plug->list)) {
+		/*
+		 * If this is the first request added after a plug, fire
+		 * of a plug trace. If others have been added before, check
+		 * if we have multiple devices in this plug. If so, make a
+		 * note to sort the list before dispatch.
+		 */
+		if (list_empty(&plug->list))
+			trace_block_plug(q);
+		else if (!plug->should_sort) {
 			struct request *__rq;
 
 			__rq = list_entry_rq(plug->list.prev);
@@ -2668,33 +2662,56 @@ static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
 	return !(rqa->q <= rqb->q);
 }
 
-static void flush_plug_list(struct blk_plug *plug)
+static void queue_unplugged(struct request_queue *q, unsigned int depth,
+			    bool force_kblockd)
+{
+	trace_block_unplug_io(q, depth);
+	__blk_run_queue(q, force_kblockd);
+
+	if (q->unplugged_fn)
+		q->unplugged_fn(q);
+}
+
+void blk_flush_plug_list(struct blk_plug *plug, bool force_kblockd)
 {
 	struct request_queue *q;
 	unsigned long flags;
 	struct request *rq;
+	LIST_HEAD(list);
+	unsigned int depth;
 
 	BUG_ON(plug->magic != PLUG_MAGIC);
 
 	if (list_empty(&plug->list))
 		return;
 
-	if (plug->should_sort)
-		list_sort(NULL, &plug->list, plug_rq_cmp);
+	list_splice_init(&plug->list, &list);
+
+	if (plug->should_sort) {
+		list_sort(NULL, &list, plug_rq_cmp);
+		plug->should_sort = 0;
+	}
 
 	q = NULL;
+	depth = 0;
+
+	/*
+	 * Save and disable interrupts here, to avoid doing it for every
+	 * queue lock we have to take.
+	 */
 	local_irq_save(flags);
-	while (!list_empty(&plug->list)) {
-		rq = list_entry_rq(plug->list.next);
+	while (!list_empty(&list)) {
+		rq = list_entry_rq(list.next);
 		list_del_init(&rq->queuelist);
 		BUG_ON(!(rq->cmd_flags & REQ_ON_PLUG));
 		BUG_ON(!rq->q);
 		if (rq->q != q) {
 			if (q) {
-				__blk_run_queue(q, false);
+				queue_unplugged(q, depth, force_kblockd);
 				spin_unlock(q->queue_lock);
 			}
 			q = rq->q;
+			depth = 0;
 			spin_lock(q->queue_lock);
 		}
 		rq->cmd_flags &= ~REQ_ON_PLUG;
@@ -2706,38 +2723,27 @@ static void flush_plug_list(struct blk_plug *plug)
 			__elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
 		else
 			__elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
+
+		depth++;
 	}
 
 	if (q) {
-		__blk_run_queue(q, false);
+		queue_unplugged(q, depth, force_kblockd);
 		spin_unlock(q->queue_lock);
 	}
 
-	BUG_ON(!list_empty(&plug->list));
 	local_irq_restore(flags);
 }
-
-static void __blk_finish_plug(struct task_struct *tsk, struct blk_plug *plug)
-{
-	flush_plug_list(plug);
-
-	if (plug == tsk->plug)
-		tsk->plug = NULL;
-}
+EXPORT_SYMBOL(blk_flush_plug_list);
 
 void blk_finish_plug(struct blk_plug *plug)
 {
-	if (plug)
-		__blk_finish_plug(current, plug);
-}
-EXPORT_SYMBOL(blk_finish_plug);
+	blk_flush_plug_list(plug, false);
 
-void __blk_flush_plug(struct task_struct *tsk, struct blk_plug *plug)
-{
-	__blk_finish_plug(tsk, plug);
-	tsk->plug = plug;
+	if (plug == current->plug)
+		current->plug = NULL;
 }
-EXPORT_SYMBOL(__blk_flush_plug);
+EXPORT_SYMBOL(blk_finish_plug);
 
 int __init blk_dev_init(void)
 {

block/blk-settings.c

@@ -790,6 +790,22 @@ void blk_queue_flush(struct request_queue *q, unsigned int flush)
 }
 EXPORT_SYMBOL_GPL(blk_queue_flush);
 
+/**
+ * blk_queue_unplugged - register a callback for an unplug event
+ * @q:		the request queue for the device
+ * @fn:		the function to call
+ *
+ * Some stacked drivers may need to know when IO is dispatched on an
+ * unplug event. By registrering a callback here, they will be notified
+ * when someone flushes their on-stack queue plug. The function will be
+ * called with the queue lock held.
+ */
+void blk_queue_unplugged(struct request_queue *q, unplugged_fn *fn)
+{
+	q->unplugged_fn = fn;
+}
+EXPORT_SYMBOL(blk_queue_unplugged);
+
 static int __init blk_settings_init(void)
 {
 	blk_max_low_pfn = max_low_pfn - 1;

block/blk-sysfs.c

@@ -498,7 +498,6 @@ int blk_register_queue(struct gendisk *disk)
 {
 	int ret;
 	struct device *dev = disk_to_dev(disk);
-
 	struct request_queue *q = disk->queue;
 
 	if (WARN_ON(!q))
@@ -521,7 +520,7 @@ int blk_register_queue(struct gendisk *disk)
 	if (ret) {
 		kobject_uevent(&q->kobj, KOBJ_REMOVE);
 		kobject_del(&q->kobj);
-		blk_trace_remove_sysfs(disk_to_dev(disk));
+		blk_trace_remove_sysfs(dev);
 		kobject_put(&dev->kobj);
 		return ret;
 	}

include/linux/blkdev.h

@@ -196,6 +196,7 @@ typedef void (request_fn_proc) (struct request_queue *q);
 typedef int (make_request_fn) (struct request_queue *q, struct bio *bio);
 typedef int (prep_rq_fn) (struct request_queue *, struct request *);
 typedef void (unprep_rq_fn) (struct request_queue *, struct request *);
+typedef void (unplugged_fn) (struct request_queue *);
 
 struct bio_vec;
 struct bvec_merge_data {
@@ -283,6 +284,7 @@ struct request_queue
 	rq_timed_out_fn		*rq_timed_out_fn;
 	dma_drain_needed_fn	*dma_drain_needed;
 	lld_busy_fn		*lld_busy_fn;
+	unplugged_fn		*unplugged_fn;
 
 	/*
 	 * Dispatch queue sorting
@@ -841,6 +843,7 @@ extern void blk_queue_dma_alignment(struct request_queue *, int);
 extern void blk_queue_update_dma_alignment(struct request_queue *, int);
 extern void blk_queue_softirq_done(struct request_queue *, softirq_done_fn *);
 extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
+extern void blk_queue_unplugged(struct request_queue *, unplugged_fn *);
 extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
 extern void blk_queue_flush(struct request_queue *q, unsigned int flush);
 extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
@@ -862,14 +865,14 @@ struct blk_plug {
 
 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 *);
+extern void blk_flush_plug_list(struct blk_plug *, bool);
 
 static inline void blk_flush_plug(struct task_struct *tsk)
 {
 	struct blk_plug *plug = tsk->plug;
 
-	if (unlikely(plug))
-		__blk_flush_plug(tsk, plug);
+	if (plug)
+		blk_flush_plug_list(plug, true);
 }
 
 static inline bool blk_needs_flush_plug(struct task_struct *tsk)

include/trace/events/block.h

@@ -401,9 +401,9 @@ TRACE_EVENT(block_plug,
 
 DECLARE_EVENT_CLASS(block_unplug,
 
-	TP_PROTO(struct request_queue *q),
+	TP_PROTO(struct request_queue *q, unsigned int depth),
 
-	TP_ARGS(q),
+	TP_ARGS(q, depth),
 
 	TP_STRUCT__entry(
 		__field( int,		nr_rq			)
@@ -411,39 +411,26 @@ DECLARE_EVENT_CLASS(block_unplug,
 	),
 
 	TP_fast_assign(
-		__entry->nr_rq	= q->rq.count[READ] + q->rq.count[WRITE];
+		__entry->nr_rq = depth;
 		memcpy(__entry->comm, current->comm, TASK_COMM_LEN);
 	),
 
 	TP_printk("[%s] %d", __entry->comm, __entry->nr_rq)
 );
 
-/**
- * block_unplug_timer - timed release of operations requests in queue to device driver
- * @q: request queue to unplug
- *
- * Unplug the request queue @q because a timer expired and allow block
- * operation requests to be sent to the device driver.
- */
-DEFINE_EVENT(block_unplug, block_unplug_timer,
-
-	TP_PROTO(struct request_queue *q),
-
-	TP_ARGS(q)
-);
-
 /**
  * block_unplug_io - release of operations requests in request queue
  * @q: request queue to unplug
+ * @depth: number of requests just added to the queue
  *
  * Unplug request queue @q because device driver is scheduled to work
  * on elements in the request queue.
  */
 DEFINE_EVENT(block_unplug, block_unplug_io,
 
-	TP_PROTO(struct request_queue *q),
+	TP_PROTO(struct request_queue *q, unsigned int depth),
 
-	TP_ARGS(q)
+	TP_ARGS(q, depth)
 );
 
 /**

kernel/trace/blktrace.c

@@ -850,32 +850,19 @@ static void blk_add_trace_plug(void *ignore, struct request_queue *q)
 		__blk_add_trace(bt, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL);
 }
 
-static void blk_add_trace_unplug_io(void *ignore, struct request_queue *q)
+static void blk_add_trace_unplug_io(void *ignore, struct request_queue *q,
+				    unsigned int depth)
 {
 	struct blk_trace *bt = q->blk_trace;
 
 	if (bt) {
-		unsigned int pdu = q->rq.count[READ] + q->rq.count[WRITE];
-		__be64 rpdu = cpu_to_be64(pdu);
+		__be64 rpdu = cpu_to_be64(depth);
 
 		__blk_add_trace(bt, 0, 0, 0, BLK_TA_UNPLUG_IO, 0,
 				sizeof(rpdu), &rpdu);
 	}
 }
 
-static void blk_add_trace_unplug_timer(void *ignore, struct request_queue *q)
-{
-	struct blk_trace *bt = q->blk_trace;
-
-	if (bt) {
-		unsigned int pdu = q->rq.count[READ] + q->rq.count[WRITE];
-		__be64 rpdu = cpu_to_be64(pdu);
-
-		__blk_add_trace(bt, 0, 0, 0, BLK_TA_UNPLUG_TIMER, 0,
-				sizeof(rpdu), &rpdu);
-	}
-}
-
 static void blk_add_trace_split(void *ignore,
 				struct request_queue *q, struct bio *bio,
 				unsigned int pdu)
@@ -1015,8 +1002,6 @@ static void blk_register_tracepoints(void)
 	WARN_ON(ret);
 	ret = register_trace_block_plug(blk_add_trace_plug, NULL);
 	WARN_ON(ret);
-	ret = register_trace_block_unplug_timer(blk_add_trace_unplug_timer, NULL);
-	WARN_ON(ret);
 	ret = register_trace_block_unplug_io(blk_add_trace_unplug_io, NULL);
 	WARN_ON(ret);
 	ret = register_trace_block_split(blk_add_trace_split, NULL);
@@ -1033,7 +1018,6 @@ static void blk_unregister_tracepoints(void)
 	unregister_trace_block_bio_remap(blk_add_trace_bio_remap, NULL);
 	unregister_trace_block_split(blk_add_trace_split, NULL);
 	unregister_trace_block_unplug_io(blk_add_trace_unplug_io, NULL);
-	unregister_trace_block_unplug_timer(blk_add_trace_unplug_timer, NULL);
 	unregister_trace_block_plug(blk_add_trace_plug, NULL);
 	unregister_trace_block_sleeprq(blk_add_trace_sleeprq, NULL);
 	unregister_trace_block_getrq(blk_add_trace_getrq, NULL);
@@ -1348,7 +1332,6 @@ static const struct {
 	[__BLK_TA_COMPLETE]	= {{  "C", "complete" },   blk_log_with_error },
 	[__BLK_TA_PLUG]		= {{  "P", "plug" },	   blk_log_plug },
 	[__BLK_TA_UNPLUG_IO]	= {{  "U", "unplug_io" },  blk_log_unplug },
-	[__BLK_TA_UNPLUG_TIMER]	= {{ "UT", "unplug_timer" }, blk_log_unplug },
 	[__BLK_TA_INSERT]	= {{  "I", "insert" },	   blk_log_generic },
 	[__BLK_TA_SPLIT]	= {{  "X", "split" },	   blk_log_split },
 	[__BLK_TA_BOUNCE]	= {{  "B", "bounce" },	   blk_log_generic },