Re: [PATCH 15/15] block: split scsi_request out of struct request

[Jens Axboe <axboe@fb.com>]

On Tue, Jan 10 2017, Christoph Hellwig wrote:
> And require all drivers that want to support BLOCK_PC to allocate it
> as the first thing of their private data.  To support this the legacy
> IDE and BSG code is switched to set cmd_size on their queues to let
> the block layer allocate the additional space.

> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index be23859..499728d 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -225,17 +225,7 @@ struct request {
>  	int tag;
>  	int errors;
>  
> -	/*
> -	 * when request is used as a packet command carrier
> -	 */
> -	unsigned char __cmd[BLK_MAX_CDB];
> -	unsigned char *cmd;
> -	unsigned short cmd_len;
> -
>  	unsigned int extra_len;	/* length of alignment and padding */
> -	unsigned int sense_len;
> -	unsigned int resid_len;	/* residual count */
> -	void *sense;

Oh yes, my mouth is watering. I've wanted to kill off ->cmd and friends
with fire for years.

On the block front, I think the solution is fine with mimicking the mq
solution of carrying an rq payload, and the implementation for the
legacy path looks fine.

-- 
Jens Axboe