Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block

* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  block: add blk_run_queue_async
  block: blk_delay_queue() should use kblockd workqueue
  md: fix up raid1/raid10 unplugging.
  md: incorporate new plugging into raid5.
  md: provide generic support for handling unplug callbacks.
  md - remove old plugging code.
  md/dm - remove remains of plug_fn callback.
  md: use new plugging interface for RAID IO.
  block: drop queue lock before calling __blk_run_queue() for kblockd punt
  Revert "block: add callback function for unplug notification"
  block: Enhance new plugging support to support general callbacks

1 files changed, 65 insertions, 18 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 78b7b0cb7216..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);
 }
 
@@ -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);
 
@@ -296,9 +297,8 @@ 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;
@@ -307,7 +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
@@ -316,6 +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
  *
@@ -328,7 +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);
@@ -977,7 +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);
@@ -1321,7 +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);
         }
@@ -2638,6 +2652,7 @@ void blk_start_plug(struct blk_plug *plug)
 
         plug->magic = PLUG_MAGIC;
         INIT_LIST_HEAD(&plug->list);
+        INIT_LIST_HEAD(&plug->cb_list);
         plug->should_sort = 0;
 
         /*
@@ -2670,12 +2685,41 @@ 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 (q->unplugged_fn)
-                q->unplugged_fn(q);
+        /*
+         * 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)
+{
+        LIST_HEAD(callbacks);
+
+        if (list_empty(&plug->cb_list))
+                return;
+
+        list_splice_init(&plug->cb_list, &callbacks);
+
+        while (!list_empty(&callbacks)) {
+                struct blk_plug_cb *cb = list_first_entry(&callbacks,
+                                                          struct blk_plug_cb,
+                                                          list);
+                list_del(&cb->list);
+                cb->callback(cb);
+        }
 }
 
 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
@@ -2688,6 +2732,7 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 
         BUG_ON(plug->magic != PLUG_MAGIC);
 
+        flush_plug_callbacks(plug);
         if (list_empty(&plug->list))
                 return;
 
@@ -2712,10 +2757,11 @@ 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);
@@ -2733,10 +2779,11 @@ 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);
 }