ipip: get rid of ipip_lock

As RTNL is held while doing tunnels inserts and deletes, we can remove
ipip_lock spinlock. My initial RCU conversion was conservative and
converted the rwlock to spinlock, with no RTNL requirement.

Use appropriate rcu annotations and modern lockdep checks as well.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 34 insertions, 33 deletions

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 3c6f8f3968a6..8de8888dc95a 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -122,11 +122,11 @@
 
 static int ipip_net_id __read_mostly;
 struct ipip_net {
-        struct ip_tunnel *tunnels_r_l[HASH_SIZE];
-        struct ip_tunnel *tunnels_r[HASH_SIZE];
-        struct ip_tunnel *tunnels_l[HASH_SIZE];
-        struct ip_tunnel *tunnels_wc[1];
-        struct ip_tunnel **tunnels[4];
+        struct ip_tunnel __rcu *tunnels_r_l[HASH_SIZE];
+        struct ip_tunnel __rcu *tunnels_r[HASH_SIZE];
+        struct ip_tunnel __rcu *tunnels_l[HASH_SIZE];
+        struct ip_tunnel __rcu *tunnels_wc[1];
+        struct ip_tunnel __rcu **tunnels[4];
 
         struct net_device *fb_tunnel_dev;
 };
@@ -135,9 +135,8 @@ static void ipip_tunnel_init(struct net_device *dev);
 static void ipip_tunnel_setup(struct net_device *dev);
 
 /*
- * Locking : hash tables are protected by RCU and a spinlock
+ * Locking : hash tables are protected by RCU and RTNL
  */
-static DEFINE_SPINLOCK(ipip_lock);
 
 #define for_each_ip_tunnel_rcu(start) \
         for (t = rcu_dereference(start); t; t = rcu_dereference(t->next))
@@ -145,8 +144,8 @@ static DEFINE_SPINLOCK(ipip_lock);
 static struct ip_tunnel * ipip_tunnel_lookup(struct net *net,
                 __be32 remote, __be32 local)
 {
-        unsigned h0 = HASH(remote);
-        unsigned h1 = HASH(local);
+        unsigned int h0 = HASH(remote);
+        unsigned int h1 = HASH(local);
         struct ip_tunnel *t;
         struct ipip_net *ipn = net_generic(net, ipip_net_id);
 
@@ -169,12 +168,12 @@ static struct ip_tunnel * ipip_tunnel_lookup(struct net *net,
         return NULL;
 }
 
-static struct ip_tunnel **__ipip_bucket(struct ipip_net *ipn,
+static struct ip_tunnel __rcu **__ipip_bucket(struct ipip_net *ipn,
                 struct ip_tunnel_parm *parms)
 {
         __be32 remote = parms->iph.daddr;
         __be32 local = parms->iph.saddr;
-        unsigned h = 0;
+        unsigned int h = 0;
         int prio = 0;
 
         if (remote) {
@@ -188,7 +187,7 @@ static struct ip_tunnel **__ipip_bucket(struct ipip_net *ipn,
         return &ipn->tunnels[prio][h];
 }
 
-static inline struct ip_tunnel **ipip_bucket(struct ipip_net *ipn,
+static inline struct ip_tunnel __rcu **ipip_bucket(struct ipip_net *ipn,
                 struct ip_tunnel *t)
 {
         return __ipip_bucket(ipn, &t->parms);
@@ -196,13 +195,14 @@ static inline struct ip_tunnel **ipip_bucket(struct ipip_net *ipn,
 
 static void ipip_tunnel_unlink(struct ipip_net *ipn, struct ip_tunnel *t)
 {
-        struct ip_tunnel **tp;
-
-        for (tp = ipip_bucket(ipn, t); *tp; tp = &(*tp)->next) {
-                if (t == *tp) {
-                        spin_lock_bh(&ipip_lock);
-                        *tp = t->next;
-                        spin_unlock_bh(&ipip_lock);
+        struct ip_tunnel __rcu **tp;
+        struct ip_tunnel *iter;
+
+        for (tp = ipip_bucket(ipn, t);
+             (iter = rtnl_dereference(*tp)) != NULL;
+             tp = &iter->next) {
+                if (t == iter) {
+                        rcu_assign_pointer(*tp, t->next);
                         break;
                 }
         }
@@ -210,12 +210,10 @@ static void ipip_tunnel_unlink(struct ipip_net *ipn, struct ip_tunnel *t)
 
 static void ipip_tunnel_link(struct ipip_net *ipn, struct ip_tunnel *t)
 {
-        struct ip_tunnel **tp = ipip_bucket(ipn, t);
+        struct ip_tunnel __rcu **tp = ipip_bucket(ipn, t);
 
-        spin_lock_bh(&ipip_lock);
-        t->next = *tp;
+        rcu_assign_pointer(t->next, rtnl_dereference(*tp));
         rcu_assign_pointer(*tp, t);
-        spin_unlock_bh(&ipip_lock);
 }
 
 static struct ip_tunnel * ipip_tunnel_locate(struct net *net,
@@ -223,12 +221,15 @@ static struct ip_tunnel * ipip_tunnel_locate(struct net *net,
 {
         __be32 remote = parms->iph.daddr;
         __be32 local = parms->iph.saddr;
-        struct ip_tunnel *t, **tp, *nt;
+        struct ip_tunnel *t, *nt;
+        struct ip_tunnel __rcu **tp;
         struct net_device *dev;
         char name[IFNAMSIZ];
         struct ipip_net *ipn = net_generic(net, ipip_net_id);
 
-        for (tp = __ipip_bucket(ipn, parms); (t = *tp) != NULL; tp = &t->next) {
+        for (tp = __ipip_bucket(ipn, parms);
+                 (t = rtnl_dereference(*tp)) != NULL;
+                 tp = &t->next) {
                 if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr)
                         return t;
         }
@@ -268,16 +269,15 @@ failed_free:
         return NULL;
 }
 
+/* called with RTNL */
 static void ipip_tunnel_uninit(struct net_device *dev)
 {
         struct net *net = dev_net(dev);
         struct ipip_net *ipn = net_generic(net, ipip_net_id);
 
-        if (dev == ipn->fb_tunnel_dev) {
-                spin_lock_bh(&ipip_lock);
-                ipn->tunnels_wc[0] = NULL;
-                spin_unlock_bh(&ipip_lock);
-        } else
+        if (dev == ipn->fb_tunnel_dev)
+                rcu_assign_pointer(ipn->tunnels_wc[0], NULL);
+        else
                 ipip_tunnel_unlink(ipn, netdev_priv(dev));
         dev_put(dev);
 }
@@ -741,7 +741,7 @@ static void __net_init ipip_fb_tunnel_init(struct net_device *dev)
         iph->ihl                = 5;
 
         dev_hold(dev);
-        ipn->tunnels_wc[0]      = tunnel;
+        rcu_assign_pointer(ipn->tunnels_wc[0], tunnel);
 }
 
 static struct xfrm_tunnel ipip_handler __read_mostly = {
@@ -760,11 +760,12 @@ static void ipip_destroy_tunnels(struct ipip_net *ipn, struct list_head *head)
         for (prio = 1; prio < 4; prio++) {
                 int h;
                 for (h = 0; h < HASH_SIZE; h++) {
-                        struct ip_tunnel *t = ipn->tunnels[prio][h];
+                        struct ip_tunnel *t;
 
+                        t = rtnl_dereference(ipn->tunnels[prio][h]);
                         while (t != NULL) {
                                 unregister_netdevice_queue(t->dev, head);
-                                t = t->next;
+                                t = rtnl_dereference(t->next);
                         }
                 }
         }