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

[Bart Van Assche <bvanassche@acm.org>]

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.