Re: [PATCH RFC v3 14/15] block: fix disordered IO in the case recursive split

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

On 8/31/25 8:32 PM, Yu Kuai wrote:
> -void submit_bio_noacct_nocheck(struct bio *bio)
> +void submit_bio_noacct_nocheck(struct bio *bio, bool split)
>   {
>   	blk_cgroup_bio_start(bio);
>   	blkcg_bio_issue_init(bio);
> @@ -745,12 +745,16 @@ void submit_bio_noacct_nocheck(struct bio *bio)
>   	 * to collect a list of requests submited by a ->submit_bio method while
>   	 * it is active, and then process them after it returned.
>   	 */
> -	if (current->bio_list)
> -		bio_list_add(&current->bio_list[0], bio);
> -	else if (!bdev_test_flag(bio->bi_bdev, BD_HAS_SUBMIT_BIO))
> +	if (current->bio_list) {
> +		if (split && !bdev_is_zoned(bio->bi_bdev))
> +			bio_list_add_head(&current->bio_list[0], bio);
> +		else
> +			bio_list_add(&current->bio_list[0], bio);

The above change will cause write errors for zoned block devices. As I
have shown before, also for zoned block devices, if a bio is split
insertion must happen at the head of the list. See e.g.
"Re: [PATCH 1/2] block: Make __submit_bio_noacct() preserve the bio 
submission order"
(https://lore.kernel.org/linux-block/a0c89df8-4b33-409c-ba43-f9543fb1b091@acm.org/)

Thanks,

Bart.