Re: [PATCH 2/4] block/mq-deadline: Add an invariant check

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2021/09/24 8:27, Bart Van Assche wrote:
> Check a statistics invariant at module unload time. When running
> blktests, the invariant is verified every time a request queue is
> removed and hence is verified at least once per test.
> 
> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Niklas Cassel <Niklas.Cassel@wdc.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  block/mq-deadline.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/block/mq-deadline.c b/block/mq-deadline.c
> index b1175e4560ad..6deb4306bcf3 100644
> --- a/block/mq-deadline.c
> +++ b/block/mq-deadline.c
> @@ -270,6 +270,12 @@ deadline_move_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
>  	deadline_remove_request(rq->q, per_prio, rq);
>  }
>  
> +/* Number of requests queued for a given priority level. */
> +static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
> +{
> +	return dd_sum(dd, inserted, prio) - dd_sum(dd, completed, prio);
> +}
> +
>  /*
>   * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
>   * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
> @@ -539,6 +545,12 @@ static void dd_exit_sched(struct elevator_queue *e)
>  
>  		WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_READ]));
>  		WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_WRITE]));
> +		WARN_ONCE(dd_queued(dd, prio) != 0,
> +			  "statistics for priority %d: i %u m %u d %u c %u\n",
> +			  prio, dd_sum(dd, inserted, prio),
> +			  dd_sum(dd, merged, prio),
> +			  dd_sum(dd, dispatched, prio),
> +			  dd_sum(dd, completed, prio));
>  	}
>  
>  	free_percpu(dd->stats);
> @@ -950,12 +962,6 @@ static int dd_async_depth_show(void *data, struct seq_file *m)
>  	return 0;
>  }
>  
> -/* Number of requests queued for a given priority level. */
> -static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
> -{
> -	return dd_sum(dd, inserted, prio) - dd_sum(dd, completed, prio);
> -}
> -
>  static int dd_queued_show(void *data, struct seq_file *m)
>  {
>  	struct request_queue *q = data;
> 

Looks good.

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

-- 
Damien Le Moal
Western Digital Research