netdev - Re: [PATCH v3 03/12] net-shapers: implement NL get operation

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Message-ID: <CAF6piCL1CyLLVSG_jM2_EWH2ESGbNX4hHv35PjQvQh5cB19BnA@mail.gmail.com>
Date: Tue, 27 Aug 2024 22:43:09 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, 
	Madhu Chittim <madhu.chittim@...el.com>, Sridhar Samudrala <sridhar.samudrala@...el.com>, 
	Simon Horman <horms@...nel.org>, John Fastabend <john.fastabend@...il.com>, 
	Sunil Kovvuri Goutham <sgoutham@...vell.com>, Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH v3 03/12] net-shapers: implement NL get operation

On 8/27/24 16:54, Jakub Kicinski wrote:
> On Tue, 27 Aug 2024 16:37:38 +0200 Paolo Abeni wrote:
>>> What's stopping anyone from diverging these 2-n sets? I mean, the whole
>>> purpose it unification and finding common ground. Once you have ops
>>> duplicated, sooner then later someone does change in A but ignore B.
>>> Having the  "preamble" in every callback seems like very good tradeoff
>>> to prevent this scenario.
>>
>> The main fact is that we do not agree on the above point - unify the
>> shaper_ops between struct net_device and struct devlink.
>>
>> I think a 3rd party opinion could help moving forward.
>> @Jakub could you please share your view here?
>
> I don't mind Jiri's suggestion. Driver can declare its own helper:
>
> static struct drv_port *
> drv_shaper_binding_to_prot(const struct net_shaper_binding *binding)
> {
>       if (binding->type == NET_SHAPER_BINDING_TYPE_NETDEV)
>               return /* netdev_priv() ? */;
>       if (binding->type == NET_SHAPER_BINDING_TYPE_DEVLINK_PORT)
>               return /* container_of() ? */;
>       WARN_ONCE();
>       return NULL;
> }
>
> And call that instead of netdev_priv()?

As I wrote this does not look like something that would help
de-deuplicate any code, but since you both seem to agree...

Double checking before I rewrote a significant amount of the core code:

In the NL API, I will replace ifindex with binding, the latter will
include nested attributes ifindex, bus_name
and dev_name.

Note that 'struct net_shaper_binding' must include a ‘struct devlink
*’ as opposed to a
‘struct devlink_port *’, as mentioned in the code snippet so far, or
we will have to drop the
shaper cache and re-introduce a get() operation.

The ops will try to fetch the net_device or devlink according to the
provided attributes.
At the moment the ops will error out with ENOTSUP for netlink object.
Most core helpers
will be re-factored to accept a 'binding *' argument in place of a
'struct net_device *'.

Full netlink support (for the brave that will implement it later) will
likely require at least an
additional scope (devlink_port), include the net_shaper_ops and
net_shaper_data inside
struct devlink, and likely code adaptation inside the core.

/P