linux-kernel - Re: [PATCH 5/6] null_blk: don't use magic numbers in the code

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Date:   Wed, 5 Oct 2022 14:05:59 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Chaitanya Kulkarni <kch@...dia.com>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     axboe@...nel.dk, johannes.thumshirn@....com, bvanassche@....org,
        ming.lei@...hat.com, shinichiro.kawasaki@....com,
        vincent.fu@...sung.com, yukuai3@...wei.com
Subject: Re: [PATCH 5/6] null_blk: don't use magic numbers in the code

On 10/5/22 12:17, Chaitanya Kulkarni wrote:
> Insteasd of using the hardcoded value use meaningful macro for tag
> available value of -1U in get_tag() and __alloc_cmd().
> 
> While at it return early on error to get rid of the extra indentation
> in __alloc_cmd().
> 
> Signed-off-by: Chaitanya Kulkarni <kch@...dia.com>

Reviewed-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>

> ---
>  drivers/block/null_blk/main.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index 765c1ca0edf5..eda5050d6dee 100644
> --- a/drivers/block/null_blk/main.c
> +++ b/drivers/block/null_blk/main.c
> @@ -24,6 +24,8 @@
>  #define TICKS_PER_SEC		50ULL
>  #define TIMER_INTERVAL		(NSEC_PER_SEC / TICKS_PER_SEC)
>  
> +#define NULL_REQ_TAG_NOT_AVAILABLE (-1U)
> +
>  #ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
>  static DECLARE_FAULT_ATTR(null_timeout_attr);
>  static DECLARE_FAULT_ATTR(null_requeue_attr);
> @@ -730,7 +732,7 @@ static unsigned int get_tag(struct nullb_queue *nq)
>  	do {
>  		tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);
>  		if (tag >= nq->queue_depth)
> -			return -1U;
> +			return NULL_REQ_TAG_NOT_AVAILABLE;
>  	} while (test_and_set_bit_lock(tag, nq->tag_map));
>  
>  	return tag;
> @@ -749,21 +751,19 @@ static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq, struct bio *bio)
>  	unsigned int tag;
>  
>  	tag = get_tag(nq);
> -	if (tag != -1U) {
> -		cmd = &nq->cmds[tag];
> -		cmd->tag = tag;
> -		cmd->error = BLK_STS_OK;
> -		cmd->nq = nq;
> -		cmd->bio = bio;
> -		if (nq->dev->irqmode == NULL_IRQ_TIMER) {
> -			hrtimer_init(&cmd->timer, CLOCK_MONOTONIC,
> -				     HRTIMER_MODE_REL);
> -			cmd->timer.function = null_cmd_timer_expired;
> -		}
> -		return cmd;
> +	if (tag == NULL_REQ_TAG_NOT_AVAILABLE)
> +		return NULL;
> +	cmd = &nq->cmds[tag];
> +	cmd->tag = tag;
> +	cmd->error = BLK_STS_OK;
> +	cmd->nq = nq;
> +	cmd->bio = bio;
> +	if (nq->dev->irqmode == NULL_IRQ_TIMER) {
> +		hrtimer_init(&cmd->timer, CLOCK_MONOTONIC,
> +				HRTIMER_MODE_REL);
> +		cmd->timer.function = null_cmd_timer_expired;
>  	}
> -
> -	return NULL;
> +	return cmd;
>  }
>  
>  static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, struct bio *bio)

-- 
Damien Le Moal
Western Digital Research