Re: [PATCH 2/3] nvme: add polling options for loop target

[Sagi Grimberg <sagi@grimberg.me>]

On 3/22/23 02:23, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> This is for mostly for testing purposes.
> 
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> ---
>   drivers/nvme/target/loop.c | 63 +++++++++++++++++++++++++++++++++++---
>   1 file changed, 58 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
> index f2d24b2d992f8..0587ead60b09e 100644
> --- a/drivers/nvme/target/loop.c
> +++ b/drivers/nvme/target/loop.c
> @@ -22,6 +22,7 @@ struct nvme_loop_iod {
>   	struct nvmet_req	req;
>   	struct nvme_loop_queue	*queue;
>   	struct work_struct	work;
> +	struct work_struct	poll;
>   	struct sg_table		sg_table;
>   	struct scatterlist	first_sgl[];
>   };
> @@ -37,6 +38,7 @@ struct nvme_loop_ctrl {
>   	struct nvme_ctrl	ctrl;
>   
>   	struct nvmet_port	*port;
> +	u32			io_queues[HCTX_MAX_TYPES];
>   };
>   
>   static inline struct nvme_loop_ctrl *to_loop_ctrl(struct nvme_ctrl *ctrl)
> @@ -76,7 +78,11 @@ static void nvme_loop_complete_rq(struct request *req)
>   	struct nvme_loop_iod *iod = blk_mq_rq_to_pdu(req);
>   
>   	sg_free_table_chained(&iod->sg_table, NVME_INLINE_SG_CNT);
> -	nvme_complete_rq(req);
> +
> +	if (req->mq_hctx->type != HCTX_TYPE_POLL || !in_interrupt())
> +		nvme_complete_rq(req);
> +	else
> +		queue_work(nvmet_wq, &iod->poll);
>   }
>   
>   static struct blk_mq_tags *nvme_loop_tagset(struct nvme_loop_queue *queue)
> @@ -120,6 +126,15 @@ static void nvme_loop_queue_response(struct nvmet_req *req)
>   	}
>   }
>   
> +static void nvme_loop_poll_work(struct work_struct *work)
> +{
> +	struct nvme_loop_iod *iod =
> +		container_of(work, struct nvme_loop_iod, poll);
> +	struct request *req = blk_mq_rq_from_pdu(iod);
> +
> +	nvme_complete_rq(req);
> +}
> +
>   static void nvme_loop_execute_work(struct work_struct *work)
>   {
>   	struct nvme_loop_iod *iod =
> @@ -170,6 +185,30 @@ static blk_status_t nvme_loop_queue_rq(struct blk_mq_hw_ctx *hctx,
>   	return BLK_STS_OK;
>   }
>   
> +static bool nvme_loop_poll_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
> +{
> +	struct blk_mq_hw_ctx *hctx = data;
> +	struct nvme_loop_iod *iod;
> +	struct request *rq;
> +
> +	rq = blk_mq_tag_to_rq(hctx->tags, bitnr);
> +	if (!rq)
> +		return true;
> +
> +	iod = blk_mq_rq_to_pdu(rq);
> +	flush_work(&iod->poll);

If we want to go down this route, I would think that maybe
it'd be better to add .poll to nvmet_req like .execute, that can
actually be wired to bio_poll ? for file it can be wired to fop.iopoll