Re: [PATCH] null_blk: add "no_sched" module parameter

[Jens Axboe <axboe@kernel.dk>]

On 09/29/2017 07:09 PM, weiping zhang wrote:
> add an option that disable io scheduler for null block device.
> 
> Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
> ---
>  drivers/block/null_blk.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
> index bd92286..3c63863 100644
> --- a/drivers/block/null_blk.c
> +++ b/drivers/block/null_blk.c
> @@ -154,6 +154,10 @@ enum {
>  	NULL_Q_MQ		= 2,
>  };
>  
> +static int g_no_sched;
> +module_param_named(no_sched, g_no_sched, int, S_IRUGO);
> +MODULE_PARM_DESC(no_sched, "No io scheduler");
> +
>  static int g_submit_queues = 1;
>  module_param_named(submit_queues, g_submit_queues, int, S_IRUGO);
>  MODULE_PARM_DESC(submit_queues, "Number of submission queues");
> @@ -1753,7 +1757,7 @@ static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set *set)
>  						g_hw_queue_depth;
>  	set->numa_node = nullb ? nullb->dev->home_node : g_home_node;
>  	set->cmd_size	= sizeof(struct nullb_cmd);
> -	set->flags = BLK_MQ_F_SHOULD_MERGE;
> +	set->flags = g_no_sched ? BLK_MQ_F_NO_SCHED : BLK_MQ_F_SHOULD_MERGE;

This should be:

	set->flags = BLK_MQ_F_SHOULD_MERGE;
	if (g_no_sched)
		set->flags |= BLK_MQ_F_NO_SCHED;

-- 
Jens Axboe