Re: [RFC PATCH 01/21] block: add and use init tagset helper

[Damien Le Moal]

On 10/5/22 12:22, Chaitanya Kulkarni wrote:
> Add and use the helper to initialize the common fields of the tag_set
> such as blk_mq_ops, number of h/w queues, queue depth, command size,
> numa_node, timeout, BLK_MQ_F_XXX flags, driver data. This initialization
> is spread all over the block drivers. This avoids the code repetation of
> the inialization code of the tag set in current block drivers and any

s/inialization/initialization
s/repetation/repetition

> future ones.
> 
> Signed-off-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
> ---
>  block/blk-mq.c                | 20 ++++++++++++++++++++
>  drivers/block/null_blk/main.c | 10 +++-------
>  include/linux/blk-mq.h        |  5 +++++
>  3 files changed, 28 insertions(+), 7 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 8070b6c10e8d..e3a8dd81bbe2 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -4341,6 +4341,26 @@ static int blk_mq_alloc_tag_set_tags(struct blk_mq_tag_set *set,
>  	return blk_mq_realloc_tag_set_tags(set, 0, new_nr_hw_queues);
>  }
>  
> +void blk_mq_init_tag_set(struct blk_mq_tag_set *set,
> +		const struct blk_mq_ops *ops, unsigned int nr_hw_queues,
> +		unsigned int queue_depth, unsigned int cmd_size, int numa_node,
> +		unsigned int timeout, unsigned int flags, void *driver_data)

That is an awful lot of arguments... I would be tempted to say pack all
these into a struct but then that would kind of negate this patchset goal.
Using a function with that many arguments will be error prone, and hard to
review... Not a fan.

> +{
> +	if (!set)
> +		return;
> +
> +	set->ops = ops;
> +	set->nr_hw_queues = nr_hw_queues;
> +	set->queue_depth = queue_depth;
> +	set->cmd_size = cmd_size;
> +	set->numa_node = numa_node;
> +	set->timeout = timeout;
> +	set->flags = flags;
> +	set->driver_data = driver_data;
> +}
> +

No blank line here.

> +EXPORT_SYMBOL_GPL(blk_mq_init_tag_set);
> +
>  /*
>   * Alloc a tag set to be associated with one or more request queues.
>   * May fail with EINVAL for various error conditions. May adjust the
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index 1f154f92f4c2..0b07aab980c4 100644
> --- a/drivers/block/null_blk/main.c
> +++ b/drivers/block/null_blk/main.c
> @@ -1926,13 +1926,9 @@ static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set *set)
>  			flags |= BLK_MQ_F_BLOCKING;
>  	}
>  
> -	set->ops = &null_mq_ops;
> -	set->cmd_size	= sizeof(struct nullb_cmd);
> -	set->flags = flags;
> -	set->driver_data = nullb;
> -	set->nr_hw_queues = hw_queues;
> -	set->queue_depth = queue_depth;
> -	set->numa_node = numa_node;
> +	blk_mq_init_tag_set(set, &null_mq_ops, hw_queues, queue_depth,
> +			sizeof(struct nullb_cmd), numa_node, 0, flags, nullb);
> +
>  	if (poll_queues) {
>  		set->nr_hw_queues += poll_queues;
>  		set->nr_maps = 3;
> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> index ba18e9bdb799..06087a8e4398 100644
> --- a/include/linux/blk-mq.h
> +++ b/include/linux/blk-mq.h
> @@ -708,6 +708,11 @@ int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
>  		struct request_queue *q);
>  void blk_mq_destroy_queue(struct request_queue *);
>  
> +

No need for the extra whiteline.

> +void blk_mq_init_tag_set(struct blk_mq_tag_set *set,
> +		const struct blk_mq_ops *ops, unsigned int nr_hw_queues,
> +		unsigned int queue_depth, unsigned int cmd_size, int numa_node,
> +		unsigned int timeout, unsigned int flags, void *driver_data);
>  int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set);
>  int blk_mq_alloc_sq_tag_set(struct blk_mq_tag_set *set,
>  		const struct blk_mq_ops *ops, unsigned int queue_depth,

-- 
Damien Le Moal
Western Digital Research