Re: [PATCHv3 1/7] blk-mq: introduce blk_map_iter

[Keith Busch <kbusch@kernel.org>]

On Wed, Jul 30, 2025 at 01:48:42PM +0530, Kanchan Joshi wrote:
> On 7/29/2025 8:04 PM, Keith Busch wrote:
> > @@ -39,12 +33,11 @@ static bool blk_map_iter_next(struct request *req, struct req_iterator *iter,
> >   	 * one could be merged into it.  This typically happens when moving to
> >   	 * the next bio, but some callers also don't pack bvecs tight.
> >   	 */
> > -	while (!iter->iter.bi_size || !iter->iter.bi_bvec_done) {
> > +	while (!iter->iter.bi_size ||
> > +	       (!iter->iter.bi_bvec_done && iter->bio->bi_next)) {
> >   		struct bio_vec next;
> >   
> >   		if (!iter->iter.bi_size) {
> > -			if (!iter->bio->bi_next)
> > -				break;
> >   			iter->bio = iter->bio->bi_next;
> >   			iter->iter = iter->bio->bi_iter;
> 
> This can crash here if we come inside the loop because 
> iter->iter.bi_size is 0
> and if this is the last bio i.e., iter->bio->bi_next is NULL?

Nah, I changed the while loop condition to ensure bio->bi_next isn't
NULL if the current bi_size is 0. But I don't recall why I moved the
condition check to there in the first place either.