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

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Message-ID: <03eade79-1727-3a31-8e31-a0a7f51b72cf@cumulusnetworks.com>
Date:   Fri, 23 Mar 2018 08:31:02 -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 3/23/18 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
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.