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

Keith Busch
2024-03-12T14:51:38Z

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?