block: get rid of QUEUE_FLAG_REENTER
[linux-2.6.git] / block / blk-core.c
index 09b2628..40725b9 100644 (file)
@@ -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);
 }
 
@@ -220,7 +220,8 @@ static void blk_delay_work(struct work_struct *work)
  */
 void blk_delay_queue(struct request_queue *q, unsigned long msecs)
 {
-       schedule_delayed_work(&q->delay_work, msecs_to_jiffies(msecs));
+       queue_delayed_work(kblockd_workqueue, &q->delay_work,
+                               msecs_to_jiffies(msecs));
 }
 EXPORT_SYMBOL(blk_delay_queue);
 
@@ -238,7 +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);
 
@@ -296,26 +297,32 @@ EXPORT_SYMBOL(blk_sync_queue);
  * Description:
  *    See @blk_run_queue. This variant must be called with 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;
 
-       /*
-        * 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)) {
-               q->request_fn(q);
-               queue_flag_clear(QUEUE_FLAG_REENTER, q);
-       } else
-               queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
+       q->request_fn(q);
 }
 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);
+}
+EXPORT_SYMBOL(blk_run_queue_async);
+
+/**
  * blk_run_queue - run a single device queue
  * @q: The queue to run
  *
@@ -328,7 +335,7 @@ 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);
@@ -977,7 +984,7 @@ 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);
@@ -1321,7 +1328,7 @@ 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);
        }
@@ -2671,9 +2678,23 @@ static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
  */
 static void queue_unplugged(struct request_queue *q, unsigned int depth,
                            bool from_schedule)
+       __releases(q->queue_lock)
 {
        trace_block_unplug(q, depth, !from_schedule);
-       __blk_run_queue(q, from_schedule);
+
+       /*
+        * If we are punting this to kblockd, then we can safely drop
+        * the queue_lock before waking kblockd (which needs to take
+        * this lock).
+        */
+       if (from_schedule) {
+               spin_unlock(q->queue_lock);
+               blk_run_queue_async(q);
+       } else {
+               __blk_run_queue(q);
+               spin_unlock(q->queue_lock);
+       }
+
 }
 
 static void flush_plug_callbacks(struct blk_plug *plug)
@@ -2729,10 +2750,11 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
                BUG_ON(!(rq->cmd_flags & REQ_ON_PLUG));
                BUG_ON(!rq->q);
                if (rq->q != q) {
-                       if (q) {
+                       /*
+                        * This drops the queue lock
+                        */
+                       if (q)
                                queue_unplugged(q, depth, from_schedule);
-                               spin_unlock(q->queue_lock);
-                       }
                        q = rq->q;
                        depth = 0;
                        spin_lock(q->queue_lock);
@@ -2750,14 +2772,14 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
                depth++;
        }
 
-       if (q) {
+       /*
+        * This drops the queue lock
+        */
+       if (q)
                queue_unplugged(q, depth, from_schedule);
-               spin_unlock(q->queue_lock);
-       }
 
        local_irq_restore(flags);
 }
-EXPORT_SYMBOL(blk_flush_plug_list);
 
 void blk_finish_plug(struct blk_plug *plug)
 {