Re: [PATCHv2 4/5] nvme: use return value from blk_execute_rq()

[Christoph Hellwig <hch@lst.de>]

On Fri, Apr 23, 2021 at 03:05:57PM -0700, Keith Busch wrote:
> We don't have an nvme status to report if the driver's .queue_rq()
> returns an error without dispatching the requested nvme command. Use the
> return value from blk_execute_rq() for all passthrough commands so the
> caller may know their command was not successful.
> 
> If the command is from the target passthrough interface and fails to
> dispatch, synthesize the response back to the host as a internal target
> error.
> 
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> ---
>  drivers/nvme/host/core.c       | 16 ++++++++++++----
>  drivers/nvme/host/ioctl.c      |  6 +-----
>  drivers/nvme/host/nvme.h       |  2 +-
>  drivers/nvme/target/passthru.c |  8 ++++----
>  4 files changed, 18 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 10bb8406e067..62af5fe7a0ce 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -972,12 +972,12 @@ int __nvme_submit_sync_cmd(struct request_queue *q, struct nvme_command *cmd,
>  			goto out;
>  	}
>  
> -	blk_execute_rq(NULL, req, at_head);
> +	ret = blk_execute_rq(NULL, req, at_head);
>  	if (result)
>  		*result = nvme_req(req)->result;
>  	if (nvme_req(req)->flags & NVME_REQ_CANCELLED)
>  		ret = -EINTR;
> -	else
> +	else if (nvme_req(req)->status)
>  		ret = nvme_req(req)->status;

Just cosmetic, and already in the existing code, but I'd prefer if we
could keep the ret assignments together, something like:

	status = blk_execute_rq(NULL, req, at_head);
  	if (nvme_req(req)->flags & NVME_REQ_CANCELLED)
 		ret = -EINTR;
	else if (nvme_req(req)->status)
		ret = nvme_req(req)->status;
	else
		ret = blk_status_to_errno(status);

 	if (result)
 		*result = nvme_req(req)->result;

> +	ret = blk_execute_rq(disk, rq, 0);
>  	if (effects) /* nothing to be done for zero cmd effects */
>  		nvme_passthru_end(ctrl, effects);
> +
> +	if (nvme_req(rq)->flags & NVME_REQ_CANCELLED)
> +		ret = -EINTR;
> +	else if (nvme_req(rq)->status)
> +		ret = nvme_req(rq)->status;
> +

I think we want a helper for all this return value magic instead of
duplicating it.