block: remove per-queue plugging

Code has been converted over to the new explicit on-stack plugging,
and delay users have been converted to use the new API for that.
So lets kill off the old plugging along with aops->sync_page().

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

10 files changed, 26 insertions, 233 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 6efb55cc5af0..82a45898ba76 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -198,6 +198,19 @@ void blk_dump_rq_flags(struct request *rq, char *msg)
 }
 EXPORT_SYMBOL(blk_dump_rq_flags);
 
+/*
+ * Make sure that plugs that were pending when this function was entered,
+ * are now complete and requests pushed to the queue.
+*/
+static inline void queue_sync_plugs(struct request_queue *q)
+{
+        /*
+         * If the current process is plugged and has barriers submitted,
+         * we will livelock if we don't unplug first.
+         */
+        blk_flush_plug(current);
+}
+
 static void blk_delay_work(struct work_struct *work)
 {
         struct request_queue *q;
@@ -224,137 +237,6 @@ void blk_delay_queue(struct request_queue *q, unsigned long msecs)
 }
 EXPORT_SYMBOL(blk_delay_queue);
 
-/*
- * "plug" the device if there are no outstanding requests: this will
- * force the transfer to start only after we have put all the requests
- * on the list.
- *
- * This is called with interrupts off and no requests on the queue and
- * with the queue lock held.
- */
-void blk_plug_device(struct request_queue *q)
-{
-        WARN_ON(!irqs_disabled());
-
-        /*
-         * don't plug a stopped queue, it must be paired with blk_start_queue()
-         * which will restart the queueing
-         */
-        if (blk_queue_stopped(q))
-                return;
-
-        if (!queue_flag_test_and_set(QUEUE_FLAG_PLUGGED, q)) {
-                mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
-                trace_block_plug(q);
-        }
-}
-EXPORT_SYMBOL(blk_plug_device);
-
-/**
- * blk_plug_device_unlocked - plug a device without queue lock held
- * @q:    The &struct request_queue to plug
- *
- * Description:
- *   Like @blk_plug_device(), but grabs the queue lock and disables
- *   interrupts.
- **/
-void blk_plug_device_unlocked(struct request_queue *q)
-{
-        unsigned long flags;
-
-        spin_lock_irqsave(q->queue_lock, flags);
-        blk_plug_device(q);
-        spin_unlock_irqrestore(q->queue_lock, flags);
-}
-EXPORT_SYMBOL(blk_plug_device_unlocked);
-
-/*
- * remove the queue from the plugged list, if present. called with
- * queue lock held and interrupts disabled.
- */
-int blk_remove_plug(struct request_queue *q)
-{
-        WARN_ON(!irqs_disabled());
-
-        if (!queue_flag_test_and_clear(QUEUE_FLAG_PLUGGED, q))
-                return 0;
-
-        del_timer(&q->unplug_timer);
-        return 1;
-}
-EXPORT_SYMBOL(blk_remove_plug);
-
-/*
- * remove the plug and let it rip..
- */
-void __generic_unplug_device(struct request_queue *q)
-{
-        if (unlikely(blk_queue_stopped(q)))
-                return;
-        if (!blk_remove_plug(q) && !blk_queue_nonrot(q))
-                return;
-
-        q->request_fn(q);
-}
-
-/**
- * generic_unplug_device - fire a request queue
- * @q:    The &struct request_queue in question
- *
- * Description:
- *   Linux uses plugging to build bigger requests queues before letting
- *   the device have at them. If a queue is plugged, the I/O scheduler
- *   is still adding and merging requests on the queue. Once the queue
- *   gets unplugged, the request_fn defined for the queue is invoked and
- *   transfers started.
- **/
-void generic_unplug_device(struct request_queue *q)
-{
-        if (blk_queue_plugged(q)) {
-                spin_lock_irq(q->queue_lock);
-                __generic_unplug_device(q);
-                spin_unlock_irq(q->queue_lock);
-        }
-}
-EXPORT_SYMBOL(generic_unplug_device);
-
-static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
-                                   struct page *page)
-{
-        struct request_queue *q = bdi->unplug_io_data;
-
-        blk_unplug(q);
-}
-
-void blk_unplug_work(struct work_struct *work)
-{
-        struct request_queue *q =
-                container_of(work, struct request_queue, unplug_work);
-
-        trace_block_unplug_io(q);
-        q->unplug_fn(q);
-}
-
-void blk_unplug_timeout(unsigned long data)
-{
-        struct request_queue *q = (struct request_queue *)data;
-
-        trace_block_unplug_timer(q);
-        kblockd_schedule_work(q, &q->unplug_work);
-}
-
-void blk_unplug(struct request_queue *q)
-{
-        /*
-         * devices don't necessarily have an ->unplug_fn defined
-         */
-        if (q->unplug_fn) {
-                trace_block_unplug_io(q);
-                q->unplug_fn(q);
-        }
-}
-EXPORT_SYMBOL(blk_unplug);
-
 /**
  * blk_start_queue - restart a previously stopped queue
  * @q:    The &struct request_queue in question
@@ -389,7 +271,6 @@ EXPORT_SYMBOL(blk_start_queue);
  **/
 void blk_stop_queue(struct request_queue *q)
 {
-        blk_remove_plug(q);
         cancel_delayed_work(&q->delay_work);
         queue_flag_set(QUEUE_FLAG_STOPPED, q);
 }
@@ -411,11 +292,10 @@ EXPORT_SYMBOL(blk_stop_queue);
  */
 void blk_sync_queue(struct request_queue *q)
 {
-        del_timer_sync(&q->unplug_timer);
         del_timer_sync(&q->timeout);
-        cancel_work_sync(&q->unplug_work);
         throtl_shutdown_timer_wq(q);
         cancel_delayed_work_sync(&q->delay_work);
+        queue_sync_plugs(q);
 }
 EXPORT_SYMBOL(blk_sync_queue);
 
@@ -430,14 +310,9 @@ EXPORT_SYMBOL(blk_sync_queue);
  */
 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.
@@ -445,10 +320,8 @@ void __blk_run_queue(struct request_queue *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);
-        }
+        } else
+                queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
 }
 EXPORT_SYMBOL(__blk_run_queue);
 
@@ -535,8 +408,6 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
         if (!q)
                 return NULL;
 
-        q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
-        q->backing_dev_info.unplug_io_data = q;
         q->backing_dev_info.ra_pages =
                         (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
         q->backing_dev_info.state = 0;
@@ -556,13 +427,11 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 
         setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
                     laptop_mode_timer_fn, (unsigned long) q);
-        init_timer(&q->unplug_timer);
         setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
         INIT_LIST_HEAD(&q->timeout_list);
         INIT_LIST_HEAD(&q->flush_queue[0]);
         INIT_LIST_HEAD(&q->flush_queue[1]);
         INIT_LIST_HEAD(&q->flush_data_in_flight);
-        INIT_WORK(&q->unplug_work, blk_unplug_work);
         INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
 
         kobject_init(&q->kobj, &blk_queue_ktype);
@@ -652,7 +521,6 @@ blk_init_allocated_queue_node(struct request_queue *q, request_fn_proc *rfn,
         q->request_fn           = rfn;
         q->prep_rq_fn           = NULL;
         q->unprep_rq_fn         = NULL;
-        q->unplug_fn            = generic_unplug_device;
         q->queue_flags          = QUEUE_FLAG_DEFAULT;
         q->queue_lock           = lock;
 
@@ -910,8 +778,8 @@ out:
 }
 
 /*
- * No available requests for this queue, unplug the device and wait for some
- * requests to become available.
+ * No available requests for this queue, wait for some requests to become
+ * available.
  *
  * Called with q->queue_lock held, and returns with it unlocked.
  */
@@ -932,7 +800,6 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
 
                 trace_block_sleeprq(q, bio, rw_flags & 1);
 
-                __generic_unplug_device(q);
                 spin_unlock_irq(q->queue_lock);
                 io_schedule();
 
@@ -1058,7 +925,7 @@ static void add_acct_request(struct request_queue *q, struct request *rq,
                              int where)
 {
         drive_stat_acct(rq, 1);
-        __elv_add_request(q, rq, where, 0);
+        __elv_add_request(q, rq, where);
 }
 
 /**
@@ -2798,7 +2665,7 @@ static void flush_plug_list(struct blk_plug *plug)
                 /*
                  * rq is already accounted, so use raw insert
                  */
-                __elv_add_request(q, rq, ELEVATOR_INSERT_SORT, 0);
+                __elv_add_request(q, rq, ELEVATOR_INSERT_SORT);
         }
 
         if (q) {
diff --git a/block/blk-exec.c b/block/blk-exec.c
index cf1456a02acd..81e31819a597 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -54,8 +54,8 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
         rq->end_io = done;
         WARN_ON(irqs_disabled());
         spin_lock_irq(q->queue_lock);
-        __elv_add_request(q, rq, where, 1);
-        __generic_unplug_device(q);
+        __elv_add_request(q, rq, where);
+        __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 1e2aa8a8908c..671fa9da7560 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -194,7 +194,6 @@ static void flush_end_io(struct request *flush_rq, int error)
 {
         struct request_queue *q = flush_rq->q;
         struct list_head *running = &q->flush_queue[q->flush_running_idx];
-        bool was_empty = elv_queue_empty(q);
         bool queued = false;
         struct request *rq, *n;
 
@@ -213,7 +212,7 @@ static void flush_end_io(struct request *flush_rq, int error)
         }
 
         /* after populating an empty queue, kick it to avoid stall */
-        if (queued && was_empty)
+        if (queued)
                 __blk_run_queue(q);
 }
 
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 36c8c1f2af18..c8d68921dddb 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -164,14 +164,6 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
         blk_queue_congestion_threshold(q);
         q->nr_batching = BLK_BATCH_REQ;
 
-        q->unplug_thresh = 4;           /* hmm */
-        q->unplug_delay = msecs_to_jiffies(3);  /* 3 milliseconds */
-        if (q->unplug_delay == 0)
-                q->unplug_delay = 1;
-
-        q->unplug_timer.function = blk_unplug_timeout;
-        q->unplug_timer.data = (unsigned long)q;
-
         blk_set_default_limits(&q->limits);
         blk_queue_max_hw_sectors(q, BLK_SAFE_MAX_SECTORS);
 
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index a89043a3caa4..b8dcdc2663a1 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -800,7 +800,6 @@ out:
         if (nr_disp) {
                 while((bio = bio_list_pop(&bio_list_on_stack)))
                         generic_make_request(bio);
-                blk_unplug(q);
         }
         return nr_disp;
 }
diff --git a/block/blk.h b/block/blk.h
index 284b500852bd..49d21af81d07 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -18,8 +18,6 @@ int blk_rq_append_bio(struct request_queue *q, struct request *rq,
 void blk_dequeue_request(struct request *rq);
 void __blk_queue_free_tags(struct request_queue *q);
 
-void blk_unplug_work(struct work_struct *work);
-void blk_unplug_timeout(unsigned long data);
 void blk_rq_timed_out_timer(unsigned long data);
 void blk_delete_timer(struct request *);
 void blk_add_timer(struct request *);
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3202c7e87fb3..ef631539dd2a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -499,13 +499,6 @@ static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
         }
 }
 
-static int cfq_queue_empty(struct request_queue *q)
-{
-        struct cfq_data *cfqd = q->elevator->elevator_data;
-
-        return !cfqd->rq_queued;
-}
-
 /*
  * Scale schedule slice based on io priority. Use the sync time slice only
  * if a queue is marked sync and has sync io queued. A sync queue with async
@@ -4061,7 +4054,6 @@ static struct elevator_type iosched_cfq = {
                 .elevator_add_req_fn =          cfq_insert_request,
                 .elevator_activate_req_fn =     cfq_activate_request,
                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
-                .elevator_queue_empty_fn =      cfq_queue_empty,
                 .elevator_completed_req_fn =    cfq_completed_request,
                 .elevator_former_req_fn =       elv_rb_former_request,
                 .elevator_latter_req_fn =       elv_rb_latter_request,
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index b547cbca7b23..5139c0ea1864 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -326,14 +326,6 @@ dispatch_request:
         return 1;
 }
 
-static int deadline_queue_empty(struct request_queue *q)
-{
-        struct deadline_data *dd = q->elevator->elevator_data;
-
-        return list_empty(&dd->fifo_list[WRITE])
-                && list_empty(&dd->fifo_list[READ]);
-}
-
 static void deadline_exit_queue(struct elevator_queue *e)
 {
         struct deadline_data *dd = e->elevator_data;
@@ -445,7 +437,6 @@ static struct elevator_type iosched_deadline = {
                 .elevator_merge_req_fn =        deadline_merged_requests,
                 .elevator_dispatch_fn =         deadline_dispatch_requests,
                 .elevator_add_req_fn =          deadline_add_request,
-                .elevator_queue_empty_fn =      deadline_queue_empty,
                 .elevator_former_req_fn =       elv_rb_former_request,
                 .elevator_latter_req_fn =       elv_rb_latter_request,
                 .elevator_init_fn =             deadline_init_queue,
diff --git a/block/elevator.c b/block/elevator.c
index 25713927c0d3..3ea208256e78 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -619,21 +619,12 @@ void elv_quiesce_end(struct request_queue *q)
 
 void elv_insert(struct request_queue *q, struct request *rq, int where)
 {
-        int unplug_it = 1;
-
         trace_block_rq_insert(q, rq);
 
         rq->q = q;
 
         switch (where) {
         case ELEVATOR_INSERT_REQUEUE:
-                /*
-                 * Most requeues happen because of a busy condition,
-                 * don't force unplug of the queue for that case.
-                 * Clear unplug_it and fall through.
-                 */
-                unplug_it = 0;
-
         case ELEVATOR_INSERT_FRONT:
                 rq->cmd_flags |= REQ_SOFTBARRIER;
                 list_add(&rq->queuelist, &q->queue_head);
@@ -679,24 +670,14 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
                 rq->cmd_flags |= REQ_SOFTBARRIER;
                 blk_insert_flush(rq);
                 break;
-
         default:
                 printk(KERN_ERR "%s: bad insertion point %d\n",
                        __func__, where);
                 BUG();
         }
-
-        if (unplug_it && blk_queue_plugged(q)) {
-                int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
-                                - queue_in_flight(q);
-
-                if (nrq >= q->unplug_thresh)
-                        __generic_unplug_device(q);
-        }
 }
 
-void __elv_add_request(struct request_queue *q, struct request *rq, int where,
-                       int plug)
+void __elv_add_request(struct request_queue *q, struct request *rq, int where)
 {
         BUG_ON(rq->cmd_flags & REQ_ON_PLUG);
 
@@ -711,38 +692,20 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where,
                     where == ELEVATOR_INSERT_SORT)
                 where = ELEVATOR_INSERT_BACK;
 
-        if (plug)
-                blk_plug_device(q);
-
         elv_insert(q, rq, where);
 }
 EXPORT_SYMBOL(__elv_add_request);
 
-void elv_add_request(struct request_queue *q, struct request *rq, int where,
-                     int plug)
+void elv_add_request(struct request_queue *q, struct request *rq, int where)
 {
         unsigned long flags;
 
         spin_lock_irqsave(q->queue_lock, flags);
-        __elv_add_request(q, rq, where, plug);
+        __elv_add_request(q, rq, where);
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
 EXPORT_SYMBOL(elv_add_request);
 
-int elv_queue_empty(struct request_queue *q)
-{
-        struct elevator_queue *e = q->elevator;
-
-        if (!list_empty(&q->queue_head))
-                return 0;
-
-        if (e->ops->elevator_queue_empty_fn)
-                return e->ops->elevator_queue_empty_fn(q);
-
-        return 1;
-}
-EXPORT_SYMBOL(elv_queue_empty);
-
 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
 {
         struct elevator_queue *e = q->elevator;
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index 232c4b38cd37..06389e9ef96d 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -39,13 +39,6 @@ static void noop_add_request(struct request_queue *q, struct request *rq)
         list_add_tail(&rq->queuelist, &nd->queue);
 }
 
-static int noop_queue_empty(struct request_queue *q)
-{
-        struct noop_data *nd = q->elevator->elevator_data;
-
-        return list_empty(&nd->queue);
-}
-
 static struct request *
 noop_former_request(struct request_queue *q, struct request *rq)
 {
@@ -90,7 +83,6 @@ static struct elevator_type elevator_noop = {
                 .elevator_merge_req_fn          = noop_merged_requests,
                 .elevator_dispatch_fn           = noop_dispatch,
                 .elevator_add_req_fn            = noop_add_request,
-                .elevator_queue_empty_fn        = noop_queue_empty,
                 .elevator_former_req_fn         = noop_former_request,
                 .elevator_latter_req_fn         = noop_latter_request,
                 .elevator_init_fn               = noop_init_queue,