net: Introduce possible_net_t

Having to say
> #ifdef CONFIG_NET_NS
> 	struct net *net;
> #endif

in structures is a little bit wordy and a little bit error prone.

Instead it is possible to say:
> typedef struct {
> #ifdef CONFIG_NET_NS
>       struct net *net;
> #endif
> } possible_net_t;

And then in a header say:

> 	possible_net_t net;

Which is cleaner and easier to use and easier to test, as the
possible_net_t is always there no matter what the compile options.

Further this allows read_pnet and write_pnet to be functions in all
cases which is better at catching typos.

This change adds possible_net_t, updates the definitions of read_pnet
and write_pnet, updates optional struct net * variables that
write_pnet uses on to have the type possible_net_t, and finally fixes
up the b0rked users of read_pnet and write_pnet.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 3 insertions, 9 deletions

diff --git a/net/ipv6/addrlabel.c b/net/ipv6/addrlabel.c
index 59c793040498..3cc50e2d3bf5 100644
--- a/net/ipv6/addrlabel.c
+++ b/net/ipv6/addrlabel.c
@@ -29,9 +29,7 @@
  * Policy Table
  */
 struct ip6addrlbl_entry {
-#ifdef CONFIG_NET_NS
-        struct net *lbl_net;
-#endif
+        possible_net_t lbl_net;
         struct in6_addr prefix;
         int prefixlen;
         int ifindex;
@@ -237,9 +235,7 @@ static struct ip6addrlbl_entry *ip6addrlbl_alloc(struct net *net,
         newp->addrtype = addrtype;
         newp->label = label;
         INIT_HLIST_NODE(&newp->list);
-#ifdef CONFIG_NET_NS
-        newp->lbl_net = net;
-#endif
+        write_pnet(&newp->lbl_net, net);
         atomic_set(&newp->refcnt, 1);
         return newp;
 }
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 34b682617f50..4b9315aa273e 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -56,9 +56,7 @@
 
 struct mr6_table {
         struct list_head        list;
-#ifdef CONFIG_NET_NS
-        struct net              *net;
-#endif
+        possible_net_t          net;
         u32                     id;
         struct sock             *mroute6_sk;
         struct timer_list       ipmr_expire_timer;