[PATCH] elv_former_request reversion

This morning's fix for elv_former_request() is causing oopses all over the
place in the IO scheduler.

Jens, remember that I did try that fix a while ago, and the same happened.

I believe it has exposed a new problem at the __make_request/attempt_front_merge
level: if attempt_front_merge() actually succeeds, the wrong request gets freed
up in elv_merged_request().

It may be best to back this change out until it can be fixed up for real.

drivers/block/elevator.c

@@ -399,7 +399,7 @@ struct request *elv_former_request(request_queue_t *q, struct request *rq)
 	elevator_t *e = &q->elevator;
 
 	if (e->elevator_former_req_fn)
-		return e->elevator_former_req_fn(q, rq);
+		return e->elevator_latter_req_fn(q, rq);
 
 	prev = rq->queuelist.prev;
 	if (prev != &q->queue_head && prev != &rq->queuelist)