1 files changed, 37 insertions, 54 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 6a343e8f8319..a16c2d1713e5 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -168,17 +168,13 @@ static struct elevator_type *elevator_get(const char *name)
         return e;
 }
 
-static void *elevator_init_queue(struct request_queue *q,
-                                 struct elevator_queue *eq)
+static int elevator_init_queue(struct request_queue *q,
+                               struct elevator_queue *eq)
 {
-        return eq->ops->elevator_init_fn(q);
-}
-
-static void elevator_attach(struct request_queue *q, struct elevator_queue *eq,
-                           void *data)
-{
-        q->elevator = eq;
-        eq->elevator_data = data;
+        eq->elevator_data = eq->ops->elevator_init_fn(q);
+        if (eq->elevator_data)
+                return 0;
+        return -ENOMEM;
 }
 
 static char chosen_elevator[ELV_NAME_MAX];
@@ -241,7 +237,7 @@ int elevator_init(struct request_queue *q, char *name)
 {
         struct elevator_type *e = NULL;
         struct elevator_queue *eq;
-        void *data;
+        int err;
 
         if (unlikely(q->elevator))
                 return 0;
@@ -278,13 +274,13 @@ int elevator_init(struct request_queue *q, char *name)
         if (!eq)
                 return -ENOMEM;
 
-        data = elevator_init_queue(q, eq);
-        if (!data) {
+        err = elevator_init_queue(q, eq);
+        if (err) {
                 kobject_put(&eq->kobj);
-                return -ENOMEM;
+                return err;
         }
 
-        elevator_attach(q, eq, data);
+        q->elevator = eq;
         return 0;
 }
 EXPORT_SYMBOL(elevator_init);
@@ -856,9 +852,8 @@ static struct kobj_type elv_ktype = {
         .release        = elevator_release,
 };
 
-int elv_register_queue(struct request_queue *q)
+int __elv_register_queue(struct request_queue *q, struct elevator_queue *e)
 {
-        struct elevator_queue *e = q->elevator;
         int error;
 
         error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
@@ -876,19 +871,22 @@ int elv_register_queue(struct request_queue *q)
         }
         return error;
 }
-EXPORT_SYMBOL(elv_register_queue);
 
-static void __elv_unregister_queue(struct elevator_queue *e)
+int elv_register_queue(struct request_queue *q)
 {
-        kobject_uevent(&e->kobj, KOBJ_REMOVE);
-        kobject_del(&e->kobj);
-        e->registered = 0;
+        return __elv_register_queue(q, q->elevator);
 }
+EXPORT_SYMBOL(elv_register_queue);
 
 void elv_unregister_queue(struct request_queue *q)
 {
-        if (q)
-                __elv_unregister_queue(q->elevator);
+        if (q) {
+                struct elevator_queue *e = q->elevator;
+
+                kobject_uevent(&e->kobj, KOBJ_REMOVE);
+                kobject_del(&e->kobj);
+                e->registered = 0;
+        }
 }
 EXPORT_SYMBOL(elv_unregister_queue);
 
@@ -928,50 +926,36 @@ EXPORT_SYMBOL_GPL(elv_unregister);
 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 {
         struct elevator_queue *old_elevator, *e;
-        void *data;
         int err;
 
-        /*
-         * Allocate new elevator
-         */
+        /* allocate new elevator */
         e = elevator_alloc(q, new_e);
         if (!e)
                 return -ENOMEM;
 
-        data = elevator_init_queue(q, e);
-        if (!data) {
+        err = elevator_init_queue(q, e);
+        if (err) {
                 kobject_put(&e->kobj);
-                return -ENOMEM;
+                return err;
         }
 
-        /*
-         * Turn on BYPASS and drain all requests w/ elevator private data
-         */
+        /* turn on BYPASS and drain all requests w/ elevator private data */
         elv_quiesce_start(q);
 
-        /*
-         * Remember old elevator.
-         */
-        old_elevator = q->elevator;
-
-        /*
-         * attach and start new elevator
-         */
-        spin_lock_irq(q->queue_lock);
-        elevator_attach(q, e, data);
-        spin_unlock_irq(q->queue_lock);
-
-        if (old_elevator->registered) {
-                __elv_unregister_queue(old_elevator);
-
-                err = elv_register_queue(q);
+        /* unregister old queue, register new one and kill old elevator */
+        if (q->elevator->registered) {
+                elv_unregister_queue(q);
+                err = __elv_register_queue(q, e);
                 if (err)
                         goto fail_register;
         }
 
-        /*
-         * finally exit old elevator and turn off BYPASS.
-         */
+        /* done, replace the old one with new one and turn off BYPASS */
+        spin_lock_irq(q->queue_lock);
+        old_elevator = q->elevator;
+        q->elevator = e;
+        spin_unlock_irq(q->queue_lock);
+
         elevator_exit(old_elevator);
         elv_quiesce_end(q);
 
@@ -985,7 +969,6 @@ fail_register:
          * one again (along with re-adding the sysfs dir)
          */
         elevator_exit(e);
-        q->elevator = old_elevator;
         elv_register_queue(q);
         elv_quiesce_end(q);