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>

6 files changed, 8 insertions, 20 deletions

diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 80d08f6664cb..3e3d82d8ff70 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -940,7 +940,7 @@ p9_fd_create_tcp(struct p9_client *client, const char *addr, char *args)
         sin_server.sin_family = AF_INET;
         sin_server.sin_addr.s_addr = in_aton(addr);
         sin_server.sin_port = htons(opts.port);
-        err = __sock_create(read_pnet(&current->nsproxy->net_ns), PF_INET,
+        err = __sock_create(current->nsproxy->net_ns, PF_INET,
                             SOCK_STREAM, IPPROTO_TCP, &csocket, 1);
         if (err) {
                 pr_err("%s (%d): problem creating socket\n",
@@ -988,7 +988,7 @@ p9_fd_create_unix(struct p9_client *client, const char *addr, char *args)
 
         sun_server.sun_family = PF_UNIX;
         strcpy(sun_server.sun_path, addr);
-        err = __sock_create(read_pnet(&current->nsproxy->net_ns), PF_UNIX,
+        err = __sock_create(current->nsproxy->net_ns, PF_UNIX,
                             SOCK_STREAM, 0, &csocket, 1);
         if (err < 0) {
                 pr_err("%s (%d): problem creating socket\n",
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 9d78427652d2..5b188832800f 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -73,9 +73,7 @@
 
 struct mr_table {
         struct list_head        list;
-#ifdef CONFIG_NET_NS
-        struct net              *net;
-#endif
+        possible_net_t          net;
         u32                     id;
         struct sock __rcu       *mroute_sk;
         struct timer_list       ipmr_expire_timer;
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;
diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
index 3ece94563079..4ec4a480b147 100644
--- a/net/openvswitch/datapath.h
+++ b/net/openvswitch/datapath.h
@@ -84,10 +84,8 @@ struct datapath {
         /* Stats. */
         struct dp_stats_percpu __percpu *stats_percpu;
 
-#ifdef CONFIG_NET_NS
         /* Network namespace ref. */
-        struct net *net;
-#endif
+        possible_net_t net;
 
         u32 user_features;
 };
diff --git a/net/packet/internal.h b/net/packet/internal.h
index cdddf6a30399..fe6e20caea1d 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -74,9 +74,7 @@ extern struct mutex fanout_mutex;
 #define PACKET_FANOUT_MAX       256
 
 struct packet_fanout {
-#ifdef CONFIG_NET_NS
-        struct net              *net;
-#endif
+        possible_net_t          net;
         unsigned int            num_members;
         u16                     id;
         u8                      type;