[PATCHv5 2/8] blk-mq-dma: provide the bio_vec list being iterated

[Christoph Hellwig]

On Fri, Aug 08, 2025 at 08:58:20AM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch at kernel.org>
> 
> This will make it easier to add different sources of the bvec table,
> like for upcoming integrity support, rather than assume to use the bio's
> bi_io_vec. It also makes iterating "special" payloads more in common
> with iterating normal payloads.

I would call the array a table (or maybe array) and not a list.

> +static struct blk_map_iter blk_rq_map_iter(struct request *rq)
> +{
> +	struct bio *bio = rq->bio;
> +
> +	if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) {
> +		return (struct blk_map_iter) {
> +			.bvec = &rq->special_vec,
> +			.iter = {
> +				.bi_size = rq->special_vec.bv_len,
> +			}
> +		};

These large struct returns generate really horrible code if they aren't
inlined (although that might happen here).  I also find them not very
nice to read.  Any reason to just pass a pointer and initialize the
needed fields?

Also this function probably should be named blk_rq_map_iter_start or
blk_rq_map_iter_init as it only is used for the very first iteration.