block: merge blk_invoke_request_fn() into __blk_run_queue()

__blk_run_queue wraps blk_invoke_request_fn() such that it
additionally removes plug and bails out early if the queue is empty.
Both extra operations have their own pending mechanisms and don't
cause any harm correctness-wise when they are done superflously.

The only user of blk_invoke_request_fn() being blk_start_queue(),
there isn't much reason to keep both functions around.  Merge
blk_invoke_request_fn() into __blk_run_queue() and make
blk_start_queue() use __blk_run_queue() instead.

[ Impact: merge two subtly different internal functions ]

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 14 insertions, 21 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 41bc0ff75e28..02f53bc00e4c 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -333,24 +333,6 @@ void blk_unplug(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_unplug);
 
-static void blk_invoke_request_fn(struct request_queue *q)
-{
-        if (unlikely(blk_queue_stopped(q)))
-                return;
-
-        /*
-         * one level of recursion is ok and is much faster than kicking
-         * the unplug handling
-         */
-        if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
-                q->request_fn(q);
-                queue_flag_clear(QUEUE_FLAG_REENTER, q);
-        } else {
-                queue_flag_set(QUEUE_FLAG_PLUGGED, q);
-                kblockd_schedule_work(q, &q->unplug_work);
-        }
-}
-
 /**
  * blk_start_queue - restart a previously stopped queue
  * @q:    The &struct request_queue in question
@@ -365,7 +347,7 @@ void blk_start_queue(struct request_queue *q)
         WARN_ON(!irqs_disabled());
 
         queue_flag_clear(QUEUE_FLAG_STOPPED, q);
-        blk_invoke_request_fn(q);
+        __blk_run_queue(q);
 }
 EXPORT_SYMBOL(blk_start_queue);
 
@@ -425,12 +407,23 @@ void __blk_run_queue(struct request_queue *q)
 {
         blk_remove_plug(q);
 
+        if (unlikely(blk_queue_stopped(q)))
+                return;
+
+        if (elv_queue_empty(q))
+                return;
+
         /*
          * Only recurse once to avoid overrunning the stack, let the unplug
          * handling reinvoke the handler shortly if we already got there.
          */
-        if (!elv_queue_empty(q))
-                blk_invoke_request_fn(q);
+        if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
+                q->request_fn(q);
+                queue_flag_clear(QUEUE_FLAG_REENTER, q);
+        } else {
+                queue_flag_set(QUEUE_FLAG_PLUGGED, q);
+                kblockd_schedule_work(q, &q->unplug_work);
+        }
 }
 EXPORT_SYMBOL(__blk_run_queue);