> On Mar 24, 2017, at 1:39 PM, Jens Axboe <axboe@xxxxxxxxx> wrote:
>
> Currently we return true in blk_mq_dispatch_rq_list() if we queued IO
> successfully, but we really want to return whether or not the we made
> progress. Progress includes if we got an error return. If we don't,
> this can lead to a hang in blk_mq_sched_dispatch_requests() when a
> driver is draining IO by returning BLK_MQ_QUEUE_ERROR instead of
> manually ending the IO in error and return BLK_MQ_QUEUE_OK.
>
> Signed-off-by: Jens Axboe <axboe@xxxxxx>
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index a4546f060e80..e3b09abf9d5b 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -978,7 +978,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
> struct request *rq;
> LIST_HEAD(driver_list);
> struct list_head *dptr;
> - int queued, ret = BLK_MQ_RQ_QUEUE_OK;
> + int errors, queued, ret = BLK_MQ_RQ_QUEUE_OK;
>
> /*
> * Start off with dptr being NULL, so we start the first request
> @@ -989,7 +989,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
> /*
> * Now process all the entries, sending them to the driver.
> */
> - queued = 0;
> + errors = queued = 0;
> while (!list_empty(list)) {
> struct blk_mq_queue_data bd;
>
> @@ -1046,6 +1046,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
> default:
> pr_err("blk-mq: bad return on queue: %d\n", ret);
> case BLK_MQ_RQ_QUEUE_ERROR:
> + errors++;
> rq->errors = -EIO;
> blk_mq_end_request(rq, rq->errors);
> break;
> @@ -1097,7 +1098,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
> blk_mq_run_hw_queue(hctx, true);
> }
>
> - return queued != 0;
> + return (queued + errors) != 0;
> }
>
> static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
>
Thanks this fixed it, you can add
Tested-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Thanks,
Josef
