Re: [PATCH V3 2/6] nvme-core: split nvme_alloc_request()

[Christoph Hellwig <hch@lst.de>]

On Wed, Oct 21, 2020 at 06:02:30PM -0700, Chaitanya Kulkarni wrote:
> +static inline unsigned int nvme_req_op(struct nvme_command *cmd)
> +{
> +	return nvme_is_write(cmd) ? REQ_OP_DRV_OUT : REQ_OP_DRV_IN;
> +}

Why is this added here while nvme_init_req_from_cmd is added in a prep
patch?  I'm actually fine either way, but doing it differnetly for the
different helpers is a little inconsistent.

> +
> +struct request *nvme_alloc_request_qid_any(struct request_queue *q,
> +		struct nvme_command *cmd, blk_mq_req_flags_t flags)

I'd call this just nvme_alloc_request to keep the short name for the
normal use case.

> +	struct request *req;
> +
> +	req = blk_mq_alloc_request(q, nvme_req_op(cmd), flags);
> +	if (unlikely(IS_ERR(req)))
> +		return req;
> +
> +	nvme_init_req_from_cmd(req, cmd);
> +	return req;

Could be simplified to:

	req = blk_mq_alloc_request(q, nvme_req_op(cmd), flags);
	if (!IS_ERR(req))
		nvme_init_req_from_cmd(req, cmd);
	return req;

Note that IS_ERR already contains an embedded unlikely().

> +static struct request *nvme_alloc_request_qid(struct request_queue *q,
>  		struct nvme_command *cmd, blk_mq_req_flags_t flags, int qid)
>  {
>  	struct request *req;
>  
> +	req = blk_mq_alloc_request_hctx(q, nvme_req_op(cmd), flags,
> +			qid ? qid - 1 : 0);
>  	if (IS_ERR(req))
>  		return req;
>  
>  	nvme_init_req_from_cmd(req, cmd);
>  	return req;

Same here.

>  }
> -EXPORT_SYMBOL_GPL(nvme_alloc_request);

I think nvme_alloc_request_qid needs to be exported as well.

FYI, this also doesn't apply to the current nvme-5.10 tree any more.