Subject: Re: [PATCH rdma-next v1 05/11] RDMA/counter: Add optional counter support

From: Jason Gunthorpe <[email-masked]>
Date: Mon, 27 Sep 2021 14:03:18 -0300

On Wed, Sep 15, 2021 at 02:07:24AM +0300, Leon Romanovsky wrote:
>  
> +int rdma_counter_modify(struct ib_device *dev, u32 port, int index, bool enable)
> +{
> +	struct rdma_hw_stats *stats;
> +	int ret;
> +
> +	if (!dev->ops.modify_hw_stat)
> +		return -EOPNOTSUPP;
> +
> +	stats = ib_get_hw_stats_port(dev, port);
> +	if (!stats)
> +		return -EINVAL;
> +
> +	mutex_lock(&stats->lock);
> +	ret = dev->ops.modify_hw_stat(dev, port, index, enable);
> +	if (!ret)
> +		enable ? clear_bit(index, stats->is_disabled) :
> +			set_bit(index, stats->is_disabled);

This is not a kernel coding style write out the if, use success
oriented flow

Also, shouldn't this logic protect the driver from being called on
non-optional counters?

>  	for (i = 0; i < data->stats->num_counters; i++) {
> -		attr = &data->attrs[i];
> +		if (data->stats->descs[i].flags & IB_STAT_FLAG_OPTIONAL)
> +			continue;
> +		attr = &data->attrs[pos];
>  		sysfs_attr_init(&attr->attr.attr);
>  		attr->attr.attr.name = data->stats->descs[i].name;
>  		attr->attr.attr.mode = 0444;
>  		attr->attr.show = hw_stat_device_show;
>  		attr->show = show_hw_stats;
> -		data->group.attrs[i] = &attr->attr.attr;
> +		data->group.attrs[pos] = &attr->attr.attr;
> +		pos++;
>  	}

This isn't OK, the hw_stat_device_show() computes the stat index like
this:

	return stat_attr->show(ibdev, ibdev->hw_stats_data->stats,
			       stat_attr - ibdev->hw_stats_data->attrs, 0, buf);

Which assumes the stats are packed contiguously. This only works
because mlx5 is always putting the optional stats at the end.

>  /**
>   * struct rdma_stat_desc
>   * @name - The name of the counter
> - *
> + * @flags - Flags of the counter; For example, IB_STAT_FLAG_OPTIONAL
>   */

The previous patch shouldn't have had the extra blank line then?

> +int rdma_counter_modify(struct ib_device *dev, u32 port, int index,
> +			bool is_add);

index should be unsigned int

The bool is called 'is_add' here but the implementation is 'enable' ?

Jason