Re: [net-next v5 6/9] netdev-genl: Support setting per-NAPI config values

[Jakub Kicinski <kuba@kernel.org>]

On Thu, 10 Oct 2024 06:24:54 +0200 Eric Dumazet wrote:
> > +static const struct netlink_range_validation netdev_a_napi_defer_hard_irqs_range = {
> > +       .max    = 2147483647ULL,  
> 
> Would (u64)INT_MAX  work ?

I sent a codegen change for this. The codegen is a bit of a mess.

> > +int netdev_nl_napi_set_doit(struct sk_buff *skb, struct genl_info *info)
> > +{
> > +       struct napi_struct *napi;
> > +       unsigned int napi_id;
> > +       int err;
> > +
> > +       if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_NAPI_ID))
> > +               return -EINVAL;
> > +
> > +       napi_id = nla_get_u32(info->attrs[NETDEV_A_NAPI_ID]);
> > +
> > +       rtnl_lock();  
> 
> Hmm.... please see my patch there :
> 
>  https://patchwork.kernel.org/project/netdevbpf/patch/20241009232728.107604-2-edumazet@google.com/
> 
> Lets not add another rtnl_lock() :/

It's not as easy since NAPIs can come and go at driver's whim.
I'm quietly hoping we can convert all netdev-nl NAPI accesses
to use the netdev->lock protection I strong-armed Paolo into 
adding in his shaper series. But perhaps we can do that after
this series? NAPI GET already takes RTNL lock.