On Tue, Aug 23, 2022 at 11:50:05PM +0900, Suwan Kim wrote:
> @@ -409,6 +409,8 @@ static bool virtblk_add_req_batch(struct virtio_blk_vq 
> *vq,
>                       virtblk_unmap_data(req, vbr);
>                       virtblk_cleanup_cmd(req);
>                       rq_list_add(requeue_list, req);
> +             } else {
> +                     blk_mq_start_request(req);
>               }

The device may see new requests as soon as virtblk_add_req() is called
above. Therefore the device may complete the request before
blk_mq_start_request() is called.

rq->io_start_time_ns = ktime_get_ns() will be after the request was
actually submitted.

I think blk_mq_start_request() needs to be called before
virtblk_add_req().

Stefan

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