linux-kernel - Re: [PATCH] blk-mq: remove needless goto from blk_mq_get_driver

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Message-ID: <2a8a99a6-4b39-e459-988a-ba9502919044@acm.org>
Date:   Wed, 23 Oct 2019 18:34:10 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     André Almeida <andrealmeid@...labora.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     axboe@...nel.dk, kernel@...labora.com, krisman@...labora.com
Subject: Re: [PATCH] blk-mq: remove needless goto from blk_mq_get_driver_tag

On 2019-10-22 10:41, André Almeida wrote:
> The only usage of the label "done" is when (rq->tag != -1) at the
> begging of the function. Rather than jumping to label, we can just
> remove this label and execute the code at the "if". Besides that,
> the code that would be executed after the label "done" is the return of
> the logical expression (rq->tag != -1) but since we are already inside
> the if, we now that this is true. Remove the label and replace the goto
> with the proper result of the label.
> 
> Signed-off-by: André Almeida <andrealmeid@...labora.com>
> ---
> Hello,
> 
> I've used `blktest` to check if this change add any regression. I have
> used `./check block` and I got the same results with and without this
> patch (a bunch of "passed" and three "not run" because of the virtual
> scsi capabilities). Please let me know if there would be a better way to
> test changes at block stack.
> 
> This commit was rebase at linux-block/for-5.5/block.
> 
> Thanks,
> 	André
> ---
>  block/blk-mq.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 8538dc415499..1e067b78ab97 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1036,7 +1036,7 @@ bool blk_mq_get_driver_tag(struct request *rq)
>  	bool shared;
>  
>  	if (rq->tag != -1)
> -		goto done;
> +		return true;
>  
>  	if (blk_mq_tag_is_reserved(data.hctx->sched_tags, rq->internal_tag))
>  		data.flags |= BLK_MQ_REQ_RESERVED;
> @@ -1051,7 +1051,6 @@ bool blk_mq_get_driver_tag(struct request *rq)
>  		data.hctx->tags->rqs[rq->tag] = rq;
>  	}
>  
> -done:
>  	return rq->tag != -1;
>  }

Do we really need code changes like the above? I'm not aware of any text
in the Documentation/ directory that forbids the use of goto statements.

Thanks,

Bart.