Re: [PATCH 3/5] block: factor out a bio_await helper

Bart Van Assche
2026-04-07T15:00:12Z

On 4/7/26 7:05 AM, Christoph Hellwig wrote:
> /**
> - * submit_bio_wait - submit a bio, and wait until it completes
> - * @bio: The &struct bio which describes the I/O
> + * bio_await - call a function on a bio, and wait until it completes
> + * @bio: the bio which describes the I/O
> + * @submit: function called to submit the bio
> + * @priv: private data passed to @submit
> *
> - * Simple wrapper around submit_bio(). Returns 0 on success, or the error from
> - * bio_endio() on failure.
> + * Wait for the bio as well as any bio chained off it after executing the
> + * passed in callback @submit. The wait for the bio is set up before calling
> + * @submit to ensure that the completion is captured. If @submit is %NULL,
> + * submit_bio() is used instead to submit the bio.
> *
> - * WARNING: Unlike to how submit_bio() is usually used, this function does not
> - * result in bio reference to be consumed. The caller must drop the reference
> - * on his own.
> + * Note: this overrides the bi_private and bi_end_io fields in the bio.
> */
> -int submit_bio_wait(struct bio *bio)
> +void bio_await(struct bio *bio, void *priv,
> + void (*submit)(struct bio *bio, void *priv))
> {
> DECLARE_COMPLETION_ONSTACK_MAP(done,
> bio->bi_bdev->bd_disk->lockdep_map);
> @@ -1486,13 +1489,37 @@ int submit_bio_wait(struct bio *bio)
> bio->bi_private = &done;
> bio->bi_end_io = bio_wait_end_io;
> bio->bi_opf |= REQ_SYNC;
> - submit_bio(bio);
> + if (submit)
> + submit(bio, priv);
> + else
> + submit_bio(bio);
> blk_wait_io(&done);
> +}
> +EXPORT_SYMBOL_GPL(bio_await);

[ ... ]

> void bio_await_chain(struct bio *bio)
> {
> - DECLARE_COMPLETION_ONSTACK_MAP(done,
> - bio->bi_bdev->bd_disk->lockdep_map);
> -
> - bio->bi_private = &done;
> - bio->bi_end_io = bio_wait_end_io;
> - bio_endio(bio);
> - blk_wait_io(&done);
> + bio_await(bio, NULL, bio_endio_cb);
> bio_put(bio);
> }
The comment above bio_await() says that the callback function passed as
third argument submits the bio. The above code passes bio_end_cb as the
"submit" argument. bio_end_cb() does something else than submitting a
bio. How about renaming the "submit" argument of bio_await() into
something else, e.g. "cb" or "callback" to make its role more clear?

Thanks,

Bart.