Re: 2.6.0-test2-mm5

[Nick Piggin <piggin@cyberone.com.au>]

Nick Piggin wrote:

> Andrew and or Martin, please test attached patch.
> Thanks.
>

Well, one of the WARN conditions I put in there is clearly
redundant...


--- linux-2.6/drivers/block/as-iosched.c.orig	2003-08-07 18:33:06.000000000 +1000
+++ linux-2.6/drivers/block/as-iosched.c	2003-08-07 18:41:50.000000000 +1000
@@ -1198,8 +1198,10 @@ static int as_dispatch_request(struct as
 			 */
 			goto dispatch_writes;
 
- 		if (ad->batch_data_dir == REQ_ASYNC)
+ 		if (ad->batch_data_dir == REQ_ASYNC) {
+			WARN_ON(ad->new_batch);
  			ad->changed_batch = 1;
+		}
 		ad->batch_data_dir = REQ_SYNC;
 		arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
 		ad->last_check_fifo[ad->batch_data_dir] = jiffies;
@@ -1214,8 +1216,16 @@ static int as_dispatch_request(struct as
 dispatch_writes:
 		BUG_ON(RB_EMPTY(&ad->sort_list[REQ_ASYNC]));
 
- 		if (ad->batch_data_dir == REQ_SYNC)
+ 		if (ad->batch_data_dir == REQ_SYNC) {
  			ad->changed_batch = 1;
+
+			/*
+			 * new_batch might be 1 when the queue runs out of
+			 * reads. A subsequent submission of a write might
+			 * cause a change of batch before the read is finished.
+			 */
+			ad->new_batch = 0;
+		}
 		ad->batch_data_dir = REQ_ASYNC;
 		ad->current_write_count = ad->write_batch_count;
 		ad->write_batch_idled = 0;