Re: [PATCH v2 2/3] blk-mq: Move more error handling into blk_mq_submit_bio()

[Damien Le Moal <dlemoal@kernel.org>]

On 2024/12/17 14:38, Bart Van Assche wrote:
> The error handling code in blk_mq_get_new_requests() cannot be understood
> without knowing that this function is only called by blk_mq_submit_bio().
> Hence move the code for handling blk_mq_get_new_requests() failures into
> blk_mq_submit_bio().
> 
> Cc: Damien Le Moal <dlemoal@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  block/blk-mq.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> 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)

No unlikely() here ?

> +		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);


-- 
Damien Le Moal
Western Digital Research