[PATCH 07/12] block: allow copying pre-registered bvecs

[Keith Busch]

On Thu, Jun 30, 2022 at 01:42:07PM -0700, Keith Busch wrote:
>  void bio_iov_bvec_set(struct bio *bio, struct iov_iter *iter)
>  {
>  	size_t size = iov_iter_count(iter);
>  
>  	WARN_ON_ONCE(bio->bi_max_vecs);
>  
> +	if (bio->bi_max_vecs) {
> +		bio_copy_bvec(bio, iter);
> +		return;
> +	}

Obviously the WARN_ON_ONCE needs to go away with this.

And with the follow on users in this series, there's also a bug with putting
page references on these at bio_endio, so don't try testing pre-registered
buffers with this series. I'll send a fix in the v2 if we get that far.