This looks generally food:
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Some cosmetic nitpicks below:
> + /*
> + * Bio splitting may cause subtle trouble such as hang
> + * when doing sync iopoll in direct IO routine. Given
> + * performance gain of iopoll for big IO can be trival,
> + * disable iopoll when split needed.
> + */
You can use up all 80 characters for comments, and doing so generally
helps readability.
> - return cookie;
> + return bio_flagged(bio, BIO_NONE_COOKIE) ? BLK_QC_T_NONE : cookie;
I'd write this a little more easily flowing as:
if (bio_flagged(bio, BIO_NONE_COOKIE))
return BLK_QC_T_NONE;
return cookie;
> queue_exit:
> blk_queue_exit(q);
> return BLK_QC_T_NONE;
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index d9b69bbde5cc..938fd25d2c68 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -284,6 +284,7 @@ enum {
> * of this bio. */
> BIO_CGROUP_ACCT, /* has been accounted to a cgroup */
> BIO_TRACKED, /* set if bio goes through the rq_qos path */
> + BIO_NONE_COOKIE, /* disable iopoll for split bio */
I'd rename this to BIO_SPLIT and update the comment. The rationale
is BIO_SPLIT is what happened to the bio. The fact that
blk_mq_submit_bio doesn't return the cookie is just one good use of
such information.
