[PATCH] AS fix

This picks up another place where aliases where getting lost.  And adds
a couple of checks.  I can't hang the osdl database thingy anymore.

The transfer alias list loops could probably quite nicely be changed to

	if (unlikely(!list_empty( old_queuelist )))
	    __list_splice( old_queuelist, new_queuelist.prev);

drivers/block/as-iosched.c

@@ -914,6 +914,8 @@ static void as_completed_request(request_queue_t *q, struct request *rq)
 	struct as_rq *arq = RQ_DATA(rq);
 	struct as_io_context *aic;
 
+	WARN_ON(!list_empty(&rq->queuelist));
+
 	if (unlikely(arq->state != AS_RQ_DISPATCHED))
 		return;
 
@@ -926,6 +928,7 @@ static void as_completed_request(request_queue_t *q, struct request *rq)
 		if (ad->batch_data_dir == REQ_SYNC)
 			ad->new_batch = 1;
 	}
+	WARN_ON(ad->nr_dispatched == 0);
 	ad->nr_dispatched--;
 
 	/*
@@ -1140,8 +1143,6 @@ static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
 	/*
 	 * take it off the sort and fifo list, add to dispatch queue
 	 */
-	as_remove_queued_request(ad->q, rq);
-
 	insert = ad->dispatch->prev;
 
 	while (!list_empty(&rq->queuelist)) {
@@ -1159,6 +1160,7 @@ static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
 		ad->nr_dispatched++;
 	}
 
+	as_remove_queued_request(ad->q, rq);
 	list_add(&rq->queuelist, insert);
 	if (arq->io_context && arq->io_context->aic)
 		atomic_inc(&arq->io_context->aic->nr_dispatched);
@@ -1325,12 +1327,27 @@ static struct request *as_next_request(request_queue_t *q)
 static inline void
 as_add_aliased_request(struct as_data *ad, struct as_rq *arq, struct as_rq *alias)
 {
+	struct request  *req = arq->request;
+	struct list_head *insert = alias->request->queuelist.prev;
+
+	/*
+	 * Transfer list of aliases
+	 */
+	while (!list_empty(&req->queuelist)) {
+		struct request *__rq = list_entry_rq(req->queuelist.next);
+		struct as_rq *__arq = RQ_DATA(__rq);
+
+		list_move_tail(&__rq->queuelist, &alias->request->queuelist);
+
+		WARN_ON(__arq->state != AS_RQ_QUEUED);
+	}
+
 	/*
 	 * Another request with the same start sector on the rbtree.
 	 * Link this request to that sector. They are untangled in
 	 * as_move_to_dispatch
 	 */
-	list_add_tail(&arq->request->queuelist, &alias->request->queuelist);
+	list_add(&arq->request->queuelist, insert);
 
 	/*
 	 * Don't want to have to handle merges.
@@ -1390,9 +1407,6 @@ static void as_add_request(struct as_data *ad, struct as_rq *arq)
 		}
 	}
 
-
-
-
 	arq->state = AS_RQ_QUEUED;
 }