Merge branch 'v2.6.36-rc8' into for-2.6.37/barrier

Conflicts:
	block/blk-core.c
	drivers/block/loop.c
	mm/swapfile.c

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

1 files changed, 37 insertions, 15 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 241c69c45c5f..282e8308f7e2 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -877,6 +877,7 @@ int elv_register_queue(struct request_queue *q)
                         }
                 }
                 kobject_uevent(&e->kobj, KOBJ_ADD);
+                e->registered = 1;
         }
         return error;
 }
@@ -886,6 +887,7 @@ static void __elv_unregister_queue(struct elevator_queue *e)
 {
         kobject_uevent(&e->kobj, KOBJ_REMOVE);
         kobject_del(&e->kobj);
+        e->registered = 0;
 }
 
 void elv_unregister_queue(struct request_queue *q)
@@ -948,18 +950,19 @@ 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
          */
         e = elevator_alloc(q, new_e);
         if (!e)
-                return 0;
+                return -ENOMEM;
 
         data = elevator_init_queue(q, e);
         if (!data) {
                 kobject_put(&e->kobj);
-                return 0;
+                return -ENOMEM;
         }
 
         /*
@@ -980,10 +983,13 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 
         spin_unlock_irq(q->queue_lock);
 
-        __elv_unregister_queue(old_elevator);
+        if (old_elevator->registered) {
+                __elv_unregister_queue(old_elevator);
 
-        if (elv_register_queue(q))
-                goto fail_register;
+                err = elv_register_queue(q);
+                if (err)
+                        goto fail_register;
+        }
 
         /*
          * finally exit old elevator and turn off BYPASS.
@@ -995,7 +1001,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 
         blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
 
-        return 1;
+        return 0;
 
 fail_register:
         /*
@@ -1010,17 +1016,19 @@ fail_register:
         queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
         spin_unlock_irq(q->queue_lock);
 
-        return 0;
+        return err;
 }
 
-ssize_t elv_iosched_store(struct request_queue *q, const char *name,
-                          size_t count)
+/*
+ * Switch this queue to the given IO scheduler.
+ */
+int elevator_change(struct request_queue *q, const char *name)
 {
         char elevator_name[ELV_NAME_MAX];
         struct elevator_type *e;
 
         if (!q->elevator)
-                return count;
+                return -ENXIO;
 
         strlcpy(elevator_name, name, sizeof(elevator_name));
         e = elevator_get(strstrip(elevator_name));
@@ -1031,13 +1039,27 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name,
 
         if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
                 elevator_put(e);
-                return count;
+                return 0;
         }
 
-        if (!elevator_switch(q, e))
-                printk(KERN_ERR "elevator: switch to %s failed\n",
-                                                        elevator_name);
-        return count;
+        return elevator_switch(q, e);
+}
+EXPORT_SYMBOL(elevator_change);
+
+ssize_t elv_iosched_store(struct request_queue *q, const char *name,
+                          size_t count)
+{
+        int ret;
+
+        if (!q->elevator)
+                return count;
+
+        ret = elevator_change(q, name);
+        if (!ret)
+                return count;
+
+        printk(KERN_ERR "elevator: switch to %s failed\n", name);
+        return ret;
 }
 
 ssize_t elv_iosched_show(struct request_queue *q, char *name)