Re: [PATCH 2/2] blk-mq: Move more error handling into blk_mq_submit_bio()

[Bart Van Assche <bvanassche@xxxxxxx>]

On 12/16/24 8:18 PM, Christoph Hellwig wrote:
> On Mon, Dec 16, 2024 at 12:19:01PM -0800, Bart Van Assche wrote:
> > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > index 8d2aab4d9ba9..80eb91296142 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -2971,8 +2971,6 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q,
> >   	if (rq)
> >   		return rq;
> >   	rq_qos_cleanup(q, bio);
> > -	if (bio->bi_opf & REQ_NOWAIT)
> > -		bio_wouldblock_error(bio);
> >   	return NULL;
>
> Please turn this into:
>
> 	if (rq)
> 		rq_qos_cleanup(q, bio);
> 	return rq;
>
> Otherwise this looks like a nice cleanup.

It seems to me that there is a typo in the above code? Unless if you 
tell me otherwise, I will assume that this is what you meant:

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8d2aab4d9ba9..f4300e608ed8 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2968,12 +2968,9 @@ static struct request 
*blk_mq_get_new_requests(struct request_queue *q,
 	}

 	rq = __blk_mq_alloc_requests(&data);
-	if (rq)
-		return rq;
-	rq_qos_cleanup(q, bio);
-	if (bio->bi_opf & REQ_NOWAIT)
-		bio_wouldblock_error(bio);
-	return NULL;
+	if (!rq)
+		rq_qos_cleanup(q, bio);
+	return rq;
 }

 /*
@@ -3106,8 +3103,11 @@ void blk_mq_submit_bio(struct bio *bio)
 		blk_mq_use_cached_rq(rq, plug, bio);
 	} else {
 		rq = blk_mq_get_new_requests(q, plug, bio, nr_segs);
-		if (unlikely(!rq))
+		if (unlikely(!rq)) {
+			if (bio->bi_opf & REQ_NOWAIT)
+				bio_wouldblock_error(bio);
 			goto queue_exit;
+		}
 	}

 	trace_block_getrq(bio);



Thanks,

Bart.