3 files changed, 28 insertions, 6 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 29825792cbd5..8768a367fdde 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -333,6 +333,7 @@ void elv_insert(request_queue_t *q, struct request *rq, int where)
 {
         struct list_head *pos;
         unsigned ordseq;
+        int unplug_it = 1;
 
         blk_add_trace_rq(q, rq, BLK_TA_INSERT);
 
@@ -399,6 +400,11 @@ void elv_insert(request_queue_t *q, struct request *rq, int where)
                 }
 
                 list_add_tail(&rq->queuelist, pos);
+                /*
+                 * most requeues happen because of a busy condition, don't
+                 * force unplug of the queue for that case.
+                 */
+                unplug_it = 0;
                 break;
 
         default:
@@ -407,7 +413,7 @@ void elv_insert(request_queue_t *q, struct request *rq, int where)
                 BUG();
         }
 
-        if (blk_queue_plugged(q)) {
+        if (unplug_it && blk_queue_plugged(q)) {
                 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
                         - q->in_flight;
 
diff --git a/block/genhd.c b/block/genhd.c
index d96572589621..5a8d3bf02f17 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -182,7 +182,6 @@ static int exact_lock(dev_t dev, void *data)
  */
 void add_disk(struct gendisk *disk)
 {
-        get_device(disk->driverfs_dev);
         disk->flags |= GENHD_FL_UP;
         blk_register_region(MKDEV(disk->major, disk->first_minor),
                             disk->minors, NULL, exact_match, exact_lock, disk);
@@ -428,7 +427,6 @@ static struct attribute * default_attrs[] = {
 static void disk_release(struct kobject * kobj)
 {
         struct gendisk *disk = to_disk(kobj);
-        put_device(disk->driverfs_dev);
         kfree(disk->random);
         kfree(disk->part);
         free_disk_stats(disk);
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index e5041a02e21f..7eb36c53f4b7 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -1732,8 +1732,21 @@ void blk_run_queue(struct request_queue *q)
 
         spin_lock_irqsave(q->queue_lock, flags);
         blk_remove_plug(q);
-        if (!elv_queue_empty(q))
-                q->request_fn(q);
+
+        /*
+         * 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)) {
+                if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
+                        q->request_fn(q);
+                        clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
+                } else {
+                        blk_plug_device(q);
+                        kblockd_schedule_work(&q->unplug_work);
+                }
+        }
+
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
 EXPORT_SYMBOL(blk_run_queue);
@@ -3439,7 +3452,12 @@ void end_that_request_last(struct request *req, int uptodate)
         if (unlikely(laptop_mode) && blk_fs_request(req))
                 laptop_io_completion();
 
-        if (disk && blk_fs_request(req)) {
+        /*
+         * Account IO completion.  bar_rq isn't accounted as a normal
+         * IO on queueing nor completion.  Accounting the containing
+         * request is enough.
+         */
+        if (disk && blk_fs_request(req) && req != &req->q->bar_rq) {
                 unsigned long duration = jiffies - req->start_time;
                 const int rw = rq_data_dir(req);