1 files changed, 41 insertions, 24 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 0d6be03d929e..a0afdd317cef 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -121,16 +121,16 @@ static struct elevator_type *elevator_get(const char *name)
         return e;
 }
 
-static int elevator_attach(request_queue_t *q, struct elevator_queue *eq)
+static void *elevator_init_queue(request_queue_t *q, struct elevator_queue *eq)
 {
-        int ret = 0;
+        return eq->ops->elevator_init_fn(q, eq);
+}
 
+static void elevator_attach(request_queue_t *q, struct elevator_queue *eq,
+                           void *data)
+{
         q->elevator = eq;
-
-        if (eq->ops->elevator_init_fn)
-                ret = eq->ops->elevator_init_fn(q, eq);
-
-        return ret;
+        eq->elevator_data = data;
 }
 
 static char chosen_elevator[16];
@@ -181,6 +181,7 @@ int elevator_init(request_queue_t *q, char *name)
         struct elevator_type *e = NULL;
         struct elevator_queue *eq;
         int ret = 0;
+        void *data;
 
         INIT_LIST_HEAD(&q->queue_head);
         q->last_merge = NULL;
@@ -202,10 +203,13 @@ int elevator_init(request_queue_t *q, char *name)
         if (!eq)
                 return -ENOMEM;
 
-        ret = elevator_attach(q, eq);
-        if (ret)
+        data = elevator_init_queue(q, eq);
+        if (!data) {
                 kobject_put(&eq->kobj);
+                return -ENOMEM;
+        }
 
+        elevator_attach(q, eq, data);
         return ret;
 }
 
@@ -333,6 +337,7 @@ 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 +404,11 @@ 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 +417,7 @@ 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;
 
@@ -716,13 +726,16 @@ int elv_register_queue(struct request_queue *q)
         return error;
 }
 
+static void __elv_unregister_queue(elevator_t *e)
+{
+        kobject_uevent(&e->kobj, KOBJ_REMOVE);
+        kobject_del(&e->kobj);
+}
+
 void elv_unregister_queue(struct request_queue *q)
 {
-        if (q) {
-                elevator_t *e = q->elevator;
-                kobject_uevent(&e->kobj, KOBJ_REMOVE);
-                kobject_del(&e->kobj);
-        }
+        if (q)
+                __elv_unregister_queue(q->elevator);
 }
 
 int elv_register(struct elevator_type *e)
@@ -774,6 +787,7 @@ EXPORT_SYMBOL_GPL(elv_unregister);
 static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
 {
         elevator_t *old_elevator, *e;
+        void *data;
 
         /*
          * Allocate new elevator
@@ -782,6 +796,12 @@ static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
         if (!e)
                 return 0;
 
+        data = elevator_init_queue(q, e);
+        if (!data) {
+                kobject_put(&e->kobj);
+                return 0;
+        }
+
         /*
          * Turn on BYPASS and drain all requests w/ elevator private data
          */
@@ -800,19 +820,19 @@ static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
                 elv_drain_elevator(q);
         }
 
-        spin_unlock_irq(q->queue_lock);
-
         /*
-         * unregister old elevator data
+         * Remember old elevator.
          */
-        elv_unregister_queue(q);
         old_elevator = q->elevator;
 
         /*
          * attach and start new elevator
          */
-        if (elevator_attach(q, e))
-                goto fail;
+        elevator_attach(q, e, data);
+
+        spin_unlock_irq(q->queue_lock);
+
+        __elv_unregister_queue(old_elevator);
 
         if (elv_register_queue(q))
                 goto fail_register;
@@ -831,7 +851,6 @@ fail_register:
          */
         elevator_exit(e);
         e = NULL;
-fail:
         q->elevator = old_elevator;
         elv_register_queue(q);
         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
@@ -895,10 +914,8 @@ ssize_t elv_iosched_show(request_queue_t *q, char *name)
 EXPORT_SYMBOL(elv_dispatch_sort);
 EXPORT_SYMBOL(elv_add_request);
 EXPORT_SYMBOL(__elv_add_request);
-EXPORT_SYMBOL(elv_requeue_request);
 EXPORT_SYMBOL(elv_next_request);
 EXPORT_SYMBOL(elv_dequeue_request);
 EXPORT_SYMBOL(elv_queue_empty);
-EXPORT_SYMBOL(elv_completed_request);
 EXPORT_SYMBOL(elevator_exit);
 EXPORT_SYMBOL(elevator_init);