netdev - Re: [PATCH net-next 1/3] lwtunnel: autoload of lwt modules

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Message-ID: <20160215170232.5f73b111@griffin>
Date:	Mon, 15 Feb 2016 17:02:32 +0100
From:	Jiri Benc <jbenc@...hat.com>
To:	Robert Shearman <rshearma@...cade.com>
Cc:	<davem@...emloft.net>, <netdev@...r.kernel.org>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	"Tom Herbert" <tom@...bertland.com>, Thomas Graf <tgraf@...g.ch>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH net-next 1/3] lwtunnel: autoload of lwt modules

On Mon, 15 Feb 2016 15:42:01 +0000, Robert Shearman wrote:
> +static const char *lwtunnel_encap_str(enum lwtunnel_encap_types encap_type)
> +{
> +	switch (encap_type) {
> +	case LWTUNNEL_ENCAP_MPLS:
> +		return "LWTUNNEL_ENCAP_MPLS";
> +	case LWTUNNEL_ENCAP_IP:
> +		return "LWTUNNEL_ENCAP_IP";
> +	case LWTUNNEL_ENCAP_ILA:
> +		return "LWTUNNEL_ENCAP_ILA";
> +	case LWTUNNEL_ENCAP_IP6:
> +		return "LWTUNNEL_ENCAP_IP6";
> +	case LWTUNNEL_ENCAP_NONE:
> +	case __LWTUNNEL_ENCAP_MAX:
> +		/* should not have got here */
> +		break;
> +	}
> +	WARN_ON(1);
> +	return "LWTUNNEL_ENCAP_NONE";
> +}
> +
> +#endif /* CONFIG_MODULES */
> +
>  struct lwtunnel_state *lwtunnel_state_alloc(int encap_len)
>  {
>  	struct lwtunnel_state *lws;
> @@ -85,6 +109,14 @@ int lwtunnel_build_state(struct net_device *dev, u16 encap_type,
>  	ret = -EOPNOTSUPP;
>  	rcu_read_lock();
>  	ops = rcu_dereference(lwtun_encaps[encap_type]);
> +#ifdef CONFIG_MODULES
> +	if (!ops) {
> +		rcu_read_unlock();
> +		request_module("rtnl-lwt-%s", lwtunnel_encap_str(encap_type));

Why the repeating of "lwt"/"LWTUNNEL" and the unnecessary "ENCAP"?
Wouldn't be lwtunnel_encap_str returning just "MPLS" or "ILA" enough?
I don't have any strong preference here, it just looks weird to me.
Maybe there's a reason.

Also, this doesn't affect IP lwtunnels, i.e. LWTUNNEL_ENCAP_IP and
LWTUNNEL_ENCAP_IP6. Should we just return NULL from lwtunnel_encap_str
in such cases (plus unknown encap_type) and WARN on the NULL here?

 Jiri

-- 
Jiri Benc