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;