[PATCH 2/5] block: add a bio_chain_and_submit helper

[Keith Busch]

On Tue, Mar 12, 2024 at 08:45:28AM -0600, Christoph Hellwig wrote:
> +struct bio *bio_chain_and_submit(struct bio *prev, struct bio *new)
>  {
> -	struct bio *new = bio_alloc(bdev, nr_pages, opf, gfp);
> -
> -	if (bio) {
> -		bio_chain(bio, new);
> -		submit_bio(bio);
> +	if (prev) {
> +		bio_chain(prev, new);
> +		submit_bio(prev);
>  	}
> -
>  	return new;
>  }
> +EXPORT_SYMBOL_GPL(bio_chain_and_submit);
> +
> +struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
> +		unsigned int nr_pages, blk_opf_t opf, gfp_t gfp)
> +{
> +	return bio_chain_and_submit(bio, bio_alloc(bdev, nr_pages, opf, gfp));
> +}

I realize you're not changing any behavior here, but I want to ask, is
bio_alloc() always guaranteed to return a valid bio? It sure looks like
it can return NULL under some uncommon conditions, but I can't find
anyone checking the result. So I guess it's safe?