Re: [PATCH rdma-next v1 06/11] RDMA/nldev: Add support to get status of all counters

[Mark Zhang <markzhang@nvidia.com>]

On 9/28/2021 7:52 PM, Jason Gunthorpe wrote:
> On Tue, Sep 28, 2021 at 05:12:39PM +0800, Mark Zhang wrote:
>> On 9/28/2021 1:30 AM, Jason Gunthorpe wrote:
>>> On Wed, Sep 15, 2021 at 02:07:25AM +0300, Leon Romanovsky wrote:
>>>> +static int stat_get_doit_default_counter(struct sk_buff *skb,
>>>> +					 struct nlmsghdr *nlh,
>>>> +					 struct netlink_ext_ack *extack,
>>>> +					 struct nlattr *tb[])
>>>> +{
>>>> +	struct rdma_hw_stats *stats;
>>>> +	struct ib_device *device;
>>>> +	u32 index, port;
>>>> +	int ret;
>>>> +
>>>> +	if (!tb[RDMA_NLDEV_ATTR_DEV_INDEX] || !tb[RDMA_NLDEV_ATTR_PORT_INDEX])
>>>> +		return -EINVAL;
>>>> +
>>>> +	index = nla_get_u32(tb[RDMA_NLDEV_ATTR_DEV_INDEX]);
>>>> +	device = ib_device_get_by_index(sock_net(skb->sk), index);
>>>> +	if (!device)
>>>> +		return -EINVAL;
>>>> +
>>>> +	port = nla_get_u32(tb[RDMA_NLDEV_ATTR_PORT_INDEX]);
>>>> +	if (!rdma_is_port_valid(device, port)) {
>>>> +		ret = -EINVAL;
>>>> +		goto end;
>>>> +	}
>>>> +
>>>> +	stats = ib_get_hw_stats_port(device, port);
>>>> +	if (!stats) {
>>>> +		ret = -EINVAL;
>>>> +		goto end;
>>>> +	}
>>>> +
>>>> +	if (tb[RDMA_NLDEV_ATTR_STAT_HWCOUNTER_DYNAMIC])
>>>> +		ret = stat_get_doit_stats_list(skb, nlh, extack, tb,
>>>> +					       device, port, stats);
>>>> +	else
>>>> +		ret = stat_get_doit_stats_values(skb, nlh, extack, tb, device,
>>>> +						 port, stats);
>>>
>>> This seems strange, why is the output of a get contingent on a ignored
>>> input attribute? Shouldn't the HWCOUNTER_DYNAMIC just always be
>>> emitted?
>>
>> The CMD_STAT_GET is originally used to get the default hwcounter statistic
>> (the value of all hwstats), now we also want to use this command to get a
>> list of counters (just name and status), so kernel differentiates these 2
>> cases based on HWCOUNTER_DYNAMIC attr.
> 
> Don't do that, it is not how netlink works. Either the whole attribute
> should be returned or you need a new get command

Will add a new get command for backward compatibility, thanks.