On Wed, Jul 01, 2020 at 06:16:17PM +0800, Ming Lei wrote:
> Current handling of q->mq_ops->queue_rq result is a bit ugly:
>
> - two branches which needs to 'continue' have to check if the
> dispatch local list is empty, otherwise one bad request may
> be retrieved via 'rq = list_first_entry(list, struct request, queuelist);'
>
> - the branch of 'if (unlikely(ret != BLK_STS_OK))' isn't easy
> to follow, since it is actually one error branch.
>
> Streamline this handling, so the code becomes more readable, meantime
> potential kernel oops can be avoided in case that the last request in
> local dispatch list is failed.
I don't really find that much easier to read. If we want to clean
this up for rea we should use a proper switch statement. Something like
this:
diff --git a/block/blk-mq.c b/block/blk-mq.c
index a9aa6d1e44cf32..f3721f274b800e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1275,30 +1275,28 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
}
ret = q->mq_ops->queue_rq(hctx, &bd);
- if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
- blk_mq_handle_dev_resource(rq, list);
+ switch (ret) {
+ case BLK_STS_OK:
+ queued++;
break;
- } else if (ret == BLK_STS_ZONE_RESOURCE) {
+ case BLK_STS_RESOURCE:
+ case BLK_STS_DEV_RESOURCE:
+ blk_mq_handle_dev_resource(rq, list);
+ goto out;
+ case BLK_STS_ZONE_RESOURCE:
/*
* Move the request to zone_list and keep going through
* the dispatch list to find more requests the drive can
* accept.
*/
blk_mq_handle_zone_resource(rq, &zone_list);
- if (list_empty(list))
- break;
- continue;
- }
-
- if (unlikely(ret != BLK_STS_OK)) {
+ break;
+ default:
errors++;
blk_mq_end_request(rq, BLK_STS_IOERR);
- continue;
}
-
- queued++;
} while (!list_empty(list));
-
+out:
if (!list_empty(&zone_list))
list_splice_tail_init(&zone_list, list);
