Re: [PATCH net-next 1/3] netlink: create a new header for internal genetlink symbols

[David Wei <dw@davidwei.uk>]

On 2024-03-09 10:34, Jakub Kicinski wrote:
> There are things in linux/genetlink.h which are only used
> under net/netlink/. Move them to a new local header.
> A new header with just 2 externs isn't great, but alternative
> would be to include af_netlink.h in genetlink.c which feels
> even worse.

Why is including af_netlink.h worse?

> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> CC: kuniyu@amazon.com
> CC: jiri@resnulli.us
> ---
>  include/linux/genetlink.h |  5 -----
>  net/netlink/af_netlink.c  |  2 +-
>  net/netlink/genetlink.c   |  2 ++
>  net/netlink/genetlink.h   | 11 +++++++++++
>  4 files changed, 14 insertions(+), 6 deletions(-)
>  create mode 100644 net/netlink/genetlink.h
> 
> diff --git a/include/linux/genetlink.h b/include/linux/genetlink.h
> index c285968e437a..9dbd7ba9b858 100644
> --- a/include/linux/genetlink.h
> +++ b/include/linux/genetlink.h
> @@ -4,15 +4,10 @@
>  
>  #include <uapi/linux/genetlink.h>
>  
> -
>  /* All generic netlink requests are serialized by a global lock.  */
>  extern void genl_lock(void);
>  extern void genl_unlock(void);
>  
> -/* for synchronisation between af_netlink and genetlink */
> -extern atomic_t genl_sk_destructing_cnt;
> -extern wait_queue_head_t genl_sk_destructing_waitq;

Checked these are only used in net/netlink/af_netlink.c and
net/netlink/genetlink.c

> -
>  #define MODULE_ALIAS_GENL_FAMILY(family)\
>   MODULE_ALIAS_NET_PF_PROTO_NAME(PF_NETLINK, NETLINK_GENERIC, "-family-" family)
>  
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index da846212fb9b..621ef3d7f044 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -59,7 +59,6 @@
>  #include <linux/rhashtable.h>
>  #include <asm/cacheflush.h>
>  #include <linux/hash.h>
> -#include <linux/genetlink.h>
>  #include <linux/net_namespace.h>
>  #include <linux/nospec.h>
>  #include <linux/btf_ids.h>
> @@ -73,6 +72,7 @@
>  #include <trace/events/netlink.h>
>  
>  #include "af_netlink.h"
> +#include "genetlink.h"
>  
>  struct listeners {
>  	struct rcu_head		rcu;
> diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
> index 3b7666944b11..feb54c63a116 100644
> --- a/net/netlink/genetlink.c
> +++ b/net/netlink/genetlink.c
> @@ -22,6 +22,8 @@
>  #include <net/sock.h>
>  #include <net/genetlink.h>
>  
> +#include "genetlink.h"
> +
>  static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */
>  static DECLARE_RWSEM(cb_lock);
>  
> diff --git a/net/netlink/genetlink.h b/net/netlink/genetlink.h
> new file mode 100644
> index 000000000000..89bd9d2631c3
> --- /dev/null
> +++ b/net/netlink/genetlink.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __NET_GENETLINK_H
> +#define __NET_GENETLINK_H
> +
> +#include <linux/wait.h>
> +
> +/* for synchronisation between af_netlink and genetlink */
> +extern atomic_t genl_sk_destructing_cnt;
> +extern wait_queue_head_t genl_sk_destructing_waitq;
> +
> +#endif	/* __LINUX_GENERIC_NETLINK_H */