1 files changed, 34 insertions, 21 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 8768a36..a0afdd3 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;
 }
 
@@ -722,13 +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)
@@ -780,6 +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
@@ -788,6 +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
 	 */
@@ -806,19 +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;
@@ -837,7 +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);