block: fixup block IO unplug trace call

It was removed with the on-stack plugging, readd it and track the
depth of requests added when flushing the plug.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

3 files changed, 22 insertions, 10 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index eeaca0998df5..d20ce1e849c8 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2668,12 +2668,19 @@ static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
         return !(rqa->q <= rqb->q);
 }
 
+static void queue_unplugged(struct request_queue *q, unsigned int depth)
+{
+        trace_block_unplug_io(q, depth);
+        __blk_run_queue(q, false);
+}
+
 static void flush_plug_list(struct blk_plug *plug)
 {
         struct request_queue *q;
         unsigned long flags;
         struct request *rq;
         LIST_HEAD(list);
+        unsigned int depth;
 
         BUG_ON(plug->magic != PLUG_MAGIC);
 
@@ -2688,6 +2695,7 @@ static void flush_plug_list(struct blk_plug *plug)
         }
 
         q = NULL;
+        depth = 0;
         local_irq_save(flags);
         while (!list_empty(&list)) {
                 rq = list_entry_rq(list.next);
@@ -2696,10 +2704,11 @@ static void flush_plug_list(struct blk_plug *plug)
                 BUG_ON(!rq->q);
                 if (rq->q != q) {
                         if (q) {
-                                __blk_run_queue(q, false);
+                                queue_unplugged(q, depth);
                                 spin_unlock(q->queue_lock);
                         }
                         q = rq->q;
+                        depth = 0;
                         spin_lock(q->queue_lock);
                 }
                 rq->cmd_flags &= ~REQ_ON_PLUG;
@@ -2711,10 +2720,12 @@ 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);
                 spin_unlock(q->queue_lock);
         }
 
diff --git a/include/trace/events/block.h b/include/trace/events/block.h
index 43a985390bb6..006e60b58306 100644
--- a/include/trace/events/block.h
+++ b/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                   )
@@ -411,7 +411,7 @@ 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);
         ),
 
@@ -421,15 +421,16 @@ DECLARE_EVENT_CLASS(block_unplug,
 /**
  * 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)
 );
 
 /**
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 824708cbfb7b..3e3970d53d14 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -850,13 +850,13 @@ 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);