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>

1 files changed, 24 insertions, 12 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);
         }