block: add blk_run_queue_async

Instead of overloading __blk_run_queue to force an offload to kblockd
add a new blk_run_queue_async helper to do it explicitly.  I've kept
the blk_queue_stopped check for now, but I suspect it's not needed
as the check we do when the workqueue items runs should be enough.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

6 files changed, 33 insertions, 20 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index e2bacfa46cc3..5fa3dd2705c6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -204,7 +204,7 @@ static void blk_delay_work(struct work_struct *work)
 
         q = container_of(work, struct request_queue, delay_work.work);
         spin_lock_irq(q->queue_lock);
-        __blk_run_queue(q, false);
+        __blk_run_queue(q);
         spin_unlock_irq(q->queue_lock);
 }
 
@@ -239,7 +239,7 @@ void blk_start_queue(struct request_queue *q)
         WARN_ON(!irqs_disabled());
 
         queue_flag_clear(QUEUE_FLAG_STOPPED, q);
-        __blk_run_queue(q, false);
+        __blk_run_queue(q);
 }
 EXPORT_SYMBOL(blk_start_queue);
 
@@ -296,11 +296,9 @@ EXPORT_SYMBOL(blk_sync_queue);
  *
  * Description:
  *    See @blk_run_queue. This variant must be called with the queue lock
- *    held and interrupts disabled. If force_kblockd is true, then it is
- *    safe to call this without holding the queue lock.
- *
+ *    held and interrupts disabled.
  */
-void __blk_run_queue(struct request_queue *q, bool force_kblockd)
+void __blk_run_queue(struct request_queue *q)
 {
         if (unlikely(blk_queue_stopped(q)))
                 return;
@@ -309,7 +307,7 @@ void __blk_run_queue(struct request_queue *q, bool force_kblockd)
          * Only recurse once to avoid overrunning the stack, let the unplug
          * handling reinvoke the handler shortly if we already got there.
          */
-        if (!force_kblockd && !queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
+        if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
                 q->request_fn(q);
                 queue_flag_clear(QUEUE_FLAG_REENTER, q);
         } else
@@ -318,6 +316,20 @@ void __blk_run_queue(struct request_queue *q, bool force_kblockd)
 EXPORT_SYMBOL(__blk_run_queue);
 
 /**
+ * blk_run_queue_async - run a single device queue in workqueue context
+ * @q:  The queue to run
+ *
+ * Description:
+ *    Tells kblockd to perform the equivalent of @blk_run_queue on behalf
+ *    of us.
+ */
+void blk_run_queue_async(struct request_queue *q)
+{
+        if (likely(!blk_queue_stopped(q)))
+                queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
+}
+
+/**
  * blk_run_queue - run a single device queue
  * @q: The queue to run
  *
@@ -330,7 +342,7 @@ void blk_run_queue(struct request_queue *q)
         unsigned long flags;
 
         spin_lock_irqsave(q->queue_lock, flags);
-        __blk_run_queue(q, false);
+        __blk_run_queue(q);
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
 EXPORT_SYMBOL(blk_run_queue);
@@ -979,7 +991,7 @@ void blk_insert_request(struct request_queue *q, struct request *rq,
                 blk_queue_end_tag(q, rq);
 
         add_acct_request(q, rq, where);
-        __blk_run_queue(q, false);
+        __blk_run_queue(q);
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
 EXPORT_SYMBOL(blk_insert_request);
@@ -1323,7 +1335,7 @@ get_rq:
         } else {
                 spin_lock_irq(q->queue_lock);
                 add_acct_request(q, req, where);
-                __blk_run_queue(q, false);
+                __blk_run_queue(q);
 out_unlock:
                 spin_unlock_irq(q->queue_lock);
         }
@@ -2684,9 +2696,9 @@ static void queue_unplugged(struct request_queue *q, unsigned int depth,
          */
         if (from_schedule) {
                 spin_unlock(q->queue_lock);
-                __blk_run_queue(q, true);
+                blk_run_queue_async(q);
         } else {
-                __blk_run_queue(q, false);
+                __blk_run_queue(q);
                 spin_unlock(q->queue_lock);
         }
 
diff --git a/block/blk-exec.c b/block/blk-exec.c
index 7482b7fa863b..81e31819a597 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -55,7 +55,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
         WARN_ON(irqs_disabled());
         spin_lock_irq(q->queue_lock);
         __elv_add_request(q, rq, where);
-        __blk_run_queue(q, false);
+        __blk_run_queue(q);
         /* the queue is stopped so it won't be plugged+unplugged */
         if (rq->cmd_type == REQ_TYPE_PM_RESUME)
                 q->request_fn(q);
diff --git a/block/blk-flush.c b/block/blk-flush.c
index eba4a2790c6c..6c9b5e189e62 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -218,7 +218,7 @@ static void flush_end_io(struct request *flush_rq, int error)
          * request_fn may confuse the driver.  Always use kblockd.
          */
         if (queued)
-                __blk_run_queue(q, true);
+                blk_run_queue_async(q);
 }
 
 /**
@@ -274,7 +274,7 @@ static void flush_data_end_io(struct request *rq, int error)
          * the comment in flush_end_io().
          */
         if (blk_flush_complete_seq(rq, REQ_FSEQ_DATA, error))
-                __blk_run_queue(q, true);
+                blk_run_queue_async(q);
 }
 
 /**
diff --git a/block/blk.h b/block/blk.h
index 61263463e38e..c9df8fc3c999 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -22,6 +22,7 @@ void blk_rq_timed_out_timer(unsigned long data);
 void blk_delete_timer(struct request *);
 void blk_add_timer(struct request *);
 void __generic_unplug_device(struct request_queue *);
+void blk_run_queue_async(struct request_queue *q);
 
 /*
  * Internal atomic flags for request handling
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3be881ec95ad..46b0a1d1d925 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3368,7 +3368,7 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                             cfqd->busy_queues > 1) {
                                 cfq_del_timer(cfqd, cfqq);
                                 cfq_clear_cfqq_wait_request(cfqq);
-                                __blk_run_queue(cfqd->queue, false);
+                                __blk_run_queue(cfqd->queue);
                         } else {
                                 cfq_blkiocg_update_idle_time_stats(
                                                 &cfqq->cfqg->blkg);
@@ -3383,7 +3383,7 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                  * this new queue is RT and the current one is BE
                  */
                 cfq_preempt_queue(cfqd, cfqq);
-                __blk_run_queue(cfqd->queue, false);
+                __blk_run_queue(cfqd->queue);
         }
 }
 
@@ -3743,7 +3743,7 @@ static void cfq_kick_queue(struct work_struct *work)
         struct request_queue *q = cfqd->queue;
 
         spin_lock_irq(q->queue_lock);
-        __blk_run_queue(cfqd->queue, false);
+        __blk_run_queue(cfqd->queue);
         spin_unlock_irq(q->queue_lock);
 }
 
diff --git a/block/elevator.c b/block/elevator.c
index 0cdb4e7ebab4..6f6abc08bb56 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -642,7 +642,7 @@ void elv_quiesce_start(struct request_queue *q)
          */
         elv_drain_elevator(q);
         while (q->rq.elvpriv) {
-                __blk_run_queue(q, false);
+                __blk_run_queue(q);
                 spin_unlock_irq(q->queue_lock);
                 msleep(10);
                 spin_lock_irq(q->queue_lock);
@@ -695,7 +695,7 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where)
                  *   with anything.  There's no point in delaying queue
                  *   processing.
                  */
-                __blk_run_queue(q, false);
+                __blk_run_queue(q);
                 break;
 
         case ELEVATOR_INSERT_SORT_MERGE: