Re: [PATCH v2 2/3] block: Split and submit bios in LBA order

[Christoph Hellwig <hch@lst.de>]

On Tue, Mar 21, 2023 at 07:03:07AM +0100, Christoph Hellwig wrote:
> > +		if (current->bio_list) {
> > +			/*
> > +			 * The caller will submit the first half ('split')
> > +			 * before the second half ('bio').
> > +			 */
> > +			bio_chain(split, bio);
> > +			submit_bio_noacct(bio);
> > +			return split;
> > +		}
> > +		/*
> > +		 * Submit the first half ('split') let the caller submit the
> > +		 * second half ('bio').
> > +		 */
> > +		*nr_segs = bio_chain_nr_segments(bio, lim);
> > +		bio_chain(split, bio);
> > +		submit_bio_noacct(split);
> 
> I'm really confused on why you want to change the behavior here
> for the case where run in a stacking context vs not, and neither
> the comments nor the commit log help me trying to figure out why.

In fact I wonder how you managed to get into __bio_split_to_limits
wtih a NULL current->bio_list at all.