Subject: Re: [PATCH] net: shrink struct net_device by #ifdef-ing protocol-specific members

From: Eric Dumazet <[email-masked]>
Date: Mon, 27 Jul 2009 16:28:16 +0200

Lucian Adrian Grijincu a écrit :
> Some members of net_device are used only by some protocols.
> 
> If those protocols are not compiled (as modules or linked in) they
> should not take up space in the structure.
> 
> These members are also used in inline functions defined in headers not
> protected by the protocol-specific CONFIG_ guards. Adding #ifdef CONFIG_*
> guards header wide is against the current style and more invasive than
> guarding only the definitions.
> 
> Signed-off-by: Lucian Adrian Grijincu <[email-masked]>
> ---
>  include/linux/inetdevice.h |    2 ++
>  include/linux/netdevice.h  |   14 ++++++++++++++
>  include/net/ax25.h         |    2 ++
>  net/core/dev.c             |    6 ++++++
>  4 files changed, 24 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
> index acef2a7..88132ff 100644
> --- a/include/linux/inetdevice.h
> +++ b/include/linux/inetdevice.h
> @@ -166,6 +166,7 @@ static __inline__ int bad_mask(__be32 mask, __be32 addr)
> 
>  #define endfor_ifa(in_dev) }
> 
> +#ifdef CONFIG_INET
>  static inline struct in_device *__in_dev_get_rcu(const struct
> net_device *dev)
>  {
>  	struct in_device *in_dev = dev->ip_ptr;
> @@ -192,6 +193,7 @@ __in_dev_get_rtnl(const struct net_device *dev)
>  {
>  	return (struct in_device*)dev->ip_ptr;
>  }
> +#endif /* CONFIG_INET */
> 
>  extern void in_dev_finish_destroy(struct in_device *idev);
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 5a96a1a..d175bb9 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -762,14 +762,28 @@ struct net_device
>  #ifdef CONFIG_NET_DSA
>  	void			*dsa_ptr;	/* dsa specific data */
>  #endif
> +#ifdef CONFIG_ATALK
>  	void 			*atalk_ptr;	/* AppleTalk link 	*/
> +#endif
> +#ifdef CONFIG_INET
>  	void			*ip_ptr;	/* IPv4 specific data	*/
> +#endif
> +#ifdef CONFIG_DECNET
>  	void                    *dn_ptr;        /* DECnet specific data */
> +#endif
> +#ifdef CONFIG_IPV6

I dont know if your patch will please that much.

For example, IPV6 can be a module, so you cannot only test 
ifdef CONFIG_IPV6

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)