netdev - Re: [PATCH RFC net-next 7/7] netdevsim: Add simple FIB resource controller via devlink

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Message-ID: <2eadcfb9-6dd2-d533-7ae3-c9299a70a172@cumulusnetworks.com>
Date:   Sat, 24 Mar 2018 09:05:38 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        roopa@...ulusnetworks.com, shm@...ulusnetworks.com,
        jiri@...lanox.com, idosch@...lanox.com,
        jakub.kicinski@...ronome.com, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH RFC net-next 7/7] netdevsim: Add simple FIB resource
 controller via devlink

On 3/24/18 1:26 AM, Jiri Pirko wrote:
> Fri, Mar 23, 2018 at 04:13:14PM CET, dsa@...ulusnetworks.com wrote:
>> On 3/23/18 9:05 AM, Jiri Pirko wrote:
>>> Fri, Mar 23, 2018 at 04:03:40PM CET, dsa@...ulusnetworks.com wrote:
>>>> On 3/23/18 9:01 AM, Jiri Pirko wrote:
>>>>> Fri, Mar 23, 2018 at 03:31:02PM CET, dsa@...ulusnetworks.com wrote:
>>>>>> On 3/23/18 12:50 AM, Jiri Pirko wrote:
>>>>>>>> +void nsim_devlink_setup(struct netdevsim *ns)
>>>>>>>> +{
>>>>>>>> +	struct net *net = dev_net(ns->netdev);
>>>>>>>> +	bool *reg_devlink = net_generic(net, nsim_devlink_id);
>>>>>>>> +	struct devlink *devlink;
>>>>>>>> +	int err = -ENOMEM;
>>>>>>>> +
>>>>>>>> +	/* only one device per namespace controls devlink */
>>>>>>>> +	if (!*reg_devlink) {
>>>>>>>> +		ns->devlink = NULL;
>>>>>>>> +		return;
>>>>>>>> +	}
>>>>>>>> +
>>>>>>>> +	devlink = devlink_alloc(&nsim_devlink_ops, 0);
>>>>>>>> +	if (!devlink)
>>>>>>>> +		return;
>>>>>>>> +
>>>>>>>> +	devlink_net_set(devlink, net);
>>>>>>>> +	err = devlink_register(devlink, &ns->dev);
>>>>>>>
>>>>>>> This reg_devlink construct looks odd. Why don't you leave the devlink
>>>>>>> instance in init_ns?
>>>>>>
>>>>>> It is a per-network namespace resource controller. Since struct devlink
>>>>>
>>>>> Wait a second. What do you mean by "per-network namespace"? Devlink
>>>>> instance is always associated with one physical device. Like an ASIC.
>>>>>
>>>>>
>>>>>> has a net entry, the simplest design is to put it into the namespace of
>>>>>> the controller. Without it, controlling resource sizes in namespace
>>>>>> 'foobar' has to be done from init_net, which is just wrong.
>>>>
>>>> you need to look at how netdevsim creates a device per netdevice.
>>>
>>> That means one devlink instance for each netdevsim device, doesn't it?
>>>
>>
>> yes.
> 
> Still not sure how to handle namespaces in devlink. Originally, I
> thought it would be okay to leave all devlink instances in init_ns.
> Because what happens if you move netdev to another namespace? Should the
> devlink move as well? What if you have multiple ports, each in different
> namespace. Can user move devlink instance to another namespace? Etc.
> 

The devlink instance is associated with a 'struct device' and those do
not change namespaces AFAIK.