On Wed, Jul 01, 2020 at 09:58:57PM +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.
>
> Fixes: fc17b6534eb8 ("blk-mq: switch ->queue_rq return value to blk_status_t")
> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> V2:
> - change 'if else' to switch as suggested by Christoph
>
> block/blk-mq.c | 24 +++++++++++-------------
> 1 file changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 65e0846fd065..cc85775fc372 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1407,30 +1407,28 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
> if (nr_budgets)
> nr_budgets--;
> 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);
>
> --
> 2.25.2
>
Hello,
Ping...
--
Ming
