[PATCH 1/4] block: add blk_rq_payload_bytes

[Sagi Grimberg]

> Add a helper to calculate the actual data transfer size for special
> payload requests.
>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  include/linux/blkdev.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index ff3d774..1ca8e8f 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1000,6 +1000,19 @@ static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
>  	return blk_rq_cur_bytes(rq) >> 9;
>  }
>
> +/*
> + * Some commands like WRITE SAME have a payload or data transfer size which

Don't you mean here DISCARD?

> + * is different from the size of the request.  Any driver that supports such
> + * commands using the RQF_SPECIAL_PAYLOAD flag needs to use this helper to
> + * calculate the data transfer size.
> + */
> +static inline unsigned int blk_rq_payload_bytes(struct request *rq)
> +{
> +	if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
> +		return rq->special_vec.bv_len;
> +	return blk_rq_bytes(rq);
> +}
> +
>  static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
>  						     int op)
>  {
>