[PATCH] block layer: elv_iosched_show should get elv_list_lock

[PATCH] block layer: elv_iosched_show should get elv_list_lock

[Vasily Tarasov]

elv_iosched_show function iterates other elv_list,
hence elv_list_lock should be got.

Also the question is: in elv_iosched_show, elv_iosched_store
q->elevator->elevator_type construction is used without locking q->queue_lock.
Is it expected?..

Signed-off-by: Vasily Tarasov <vtaras@openvz.org>

--

--- linux-2.6.18/block/elevator.c.orig	2006-10-11 11:00:34.000000000 +0400
+++ linux-2.6.18/block/elevator.c	2006-10-11 15:08:20.000000000 +0400
@@ -892,7 +892,7 @@ ssize_t elv_iosched_show(request_queue_t
 	struct list_head *entry;
 	int len = 0;
 
-	spin_lock_irq(q->queue_lock);
+	spin_lock_irq(&elv_list_lock);
 	list_for_each(entry, &elv_list) {
 		struct elevator_type *__e;
 
@@ -902,7 +902,7 @@ ssize_t elv_iosched_show(request_queue_t
 		else
 			len += sprintf(name+len, "%s ", __e->elevator_name);
 	}
-	spin_unlock_irq(q->queue_lock);
+	spin_unlock_irq(&elv_list_lock);
 
 	len += sprintf(len+name, "\n");
 	return len;

Re: [PATCH] block layer: elv_iosched_show should get elv_list_lock

[Jens Axboe]

On Wed, Oct 11 2006, Vasily Tarasov wrote:
> elv_iosched_show function iterates other elv_list,
> hence elv_list_lock should be got.

Indeed, that's a bug. Thanks!

> Also the question is: in elv_iosched_show, elv_iosched_store
> q->elevator->elevator_type construction is used without locking
> q->queue_lock.  Is it expected?..

As long as the queue doesn't go away, we should be safe enough.

-- 
Jens Axboe