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Subject: Re: [PATCH rdma-next v1 06/11] RDMA/nldev: Add support to get status
 of all counters
To:     Jason Gunthorpe <jgg@nvidia.com>
CC:     Leon Romanovsky <leon@kernel.org>,
        Doug Ledford <dledford@redhat.com>,
        Aharon Landau <aharonl@nvidia.com>,
        "David S. Miller" <davem@davemloft.net>,
        Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>,
        Gal Pressman <galpress@amazon.com>,
        Jakub Kicinski <kuba@kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-rdma@vger.kernel.org>,
        Maor Gottlieb <maorg@nvidia.com>,
        Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>,
        Mustafa Ismail <mustafa.ismail@intel.com>,
        Naresh Kumar PBS <nareshkumar.pbs@broadcom.com>,
        Neta Ostrovsky <netao@nvidia.com>, <netdev@vger.kernel.org>,
        Potnuri Bharat Teja <bharat@chelsio.com>,
        "Saeed Mahameed" <saeedm@nvidia.com>,
        Selvin Xavier <selvin.xavier@broadcom.com>,
        Shiraz Saleem <shiraz.saleem@intel.com>,
        Yishai Hadas <yishaih@nvidia.com>,
        Zhu Yanjun <zyjzyj2000@gmail.com>
References: <cover.1631660727.git.leonro@nvidia.com>
 <86b8a508d7e782b003d60acb06536681f0d4c721.1631660727.git.leonro@nvidia.com>
 <20210927173001.GD1529966@nvidia.com>
 <d812f553-1fc5-f228-18cb-07dce02eeb85@nvidia.com>
 <20210928115217.GI964074@nvidia.com>
From:   Mark Zhang <markzhang@nvidia.com>
Message-ID: <d71e2841-43b1-9be2-40f5-e9fb50400904@nvidia.com>
Date:   Tue, 28 Sep 2021 20:51:11 +0800
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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.