On Wed, Jul 30, 2025 at 01:48:42PM +0530, Kanchan Joshi wrote:

On 7/29/2025 8:04 PM, Keith Busch wrote:

quoted

@@ -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.