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

[Mark Zhang <markzhang@nvidia.com>]

On 9/28/2021 1:03 AM, Jason Gunthorpe wrote:
> 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?

We leave it to driver, driver would return failure if modify is not 
supported. Is it good?

>>   	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.

Yes you are right, thanks. Maybe we can add an "index" field in struct 
hw_stats_device/port_attribute, then set it in setup and use it in show.