ip6tnl: get rid of ip6_tnl_lock

As RTNL is held while doing tunnels inserts and deletes, we can remove
ip6_tnl_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, 28 insertions, 30 deletions

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 29f99dd75bc6..9289cecac4de 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -83,15 +83,14 @@ struct ip6_tnl_net {
         /* the IPv6 tunnel fallback device */
         struct net_device *fb_tnl_dev;
         /* lists for storing tunnels in use */
-        struct ip6_tnl *tnls_r_l[HASH_SIZE];
-        struct ip6_tnl *tnls_wc[1];
-        struct ip6_tnl **tnls[2];
+        struct ip6_tnl __rcu *tnls_r_l[HASH_SIZE];
+        struct ip6_tnl __rcu *tnls_wc[1];
+        struct ip6_tnl __rcu **tnls[2];
 };
 
 /*
- * Locking : hash tables are protected by RCU and a spinlock
+ * Locking : hash tables are protected by RCU and RTNL
  */
-static DEFINE_SPINLOCK(ip6_tnl_lock);
 
 static inline struct dst_entry *ip6_tnl_dst_check(struct ip6_tnl *t)
 {
@@ -138,8 +137,8 @@ static inline void ip6_tnl_dst_store(struct ip6_tnl *t, struct dst_entry *dst)
 static struct ip6_tnl *
 ip6_tnl_lookup(struct net *net, struct in6_addr *remote, struct in6_addr *local)
 {
-        unsigned h0 = HASH(remote);
-        unsigned h1 = HASH(local);
+        unsigned int h0 = HASH(remote);
+        unsigned int h1 = HASH(local);
         struct ip6_tnl *t;
         struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
 
@@ -167,7 +166,7 @@ ip6_tnl_lookup(struct net *net, struct in6_addr *remote, struct in6_addr *local)
  * Return: head of IPv6 tunnel list
  **/
 
-static struct ip6_tnl **
+static struct ip6_tnl __rcu **
 ip6_tnl_bucket(struct ip6_tnl_net *ip6n, struct ip6_tnl_parm *p)
 {
         struct in6_addr *remote = &p->raddr;
@@ -190,12 +189,10 @@ ip6_tnl_bucket(struct ip6_tnl_net *ip6n, struct ip6_tnl_parm *p)
 static void
 ip6_tnl_link(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
 {
-        struct ip6_tnl **tp = ip6_tnl_bucket(ip6n, &t->parms);
+        struct ip6_tnl __rcu **tp = ip6_tnl_bucket(ip6n, &t->parms);
 
-        spin_lock_bh(&ip6_tnl_lock);
-        t->next = *tp;
+        rcu_assign_pointer(t->next , rtnl_dereference(*tp));
         rcu_assign_pointer(*tp, t);
-        spin_unlock_bh(&ip6_tnl_lock);
 }
 
 /**
@@ -206,13 +203,14 @@ ip6_tnl_link(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
 static void
 ip6_tnl_unlink(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
 {
-        struct ip6_tnl **tp;
-
-        for (tp = ip6_tnl_bucket(ip6n, &t->parms); *tp; tp = &(*tp)->next) {
-                if (t == *tp) {
-                        spin_lock_bh(&ip6_tnl_lock);
-                        *tp = t->next;
-                        spin_unlock_bh(&ip6_tnl_lock);
+        struct ip6_tnl __rcu **tp;
+        struct ip6_tnl *iter;
+
+        for (tp = ip6_tnl_bucket(ip6n, &t->parms);
+             (iter = rtnl_dereference(*tp)) != NULL;
+             tp = &iter->next) {
+                if (t == iter) {
+                        rcu_assign_pointer(*tp, t->next);
                         break;
                 }
         }
@@ -290,10 +288,13 @@ static struct ip6_tnl *ip6_tnl_locate(struct net *net,
 {
         struct in6_addr *remote = &p->raddr;
         struct in6_addr *local = &p->laddr;
+        struct ip6_tnl __rcu **tp;
         struct ip6_tnl *t;
         struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
 
-        for (t = *ip6_tnl_bucket(ip6n, p); t; t = t->next) {
+        for (tp = ip6_tnl_bucket(ip6n, p);
+             (t = rtnl_dereference(*tp)) != NULL;
+             tp = &t->next) {
                 if (ipv6_addr_equal(local, &t->parms.laddr) &&
                     ipv6_addr_equal(remote, &t->parms.raddr))
                         return t;
@@ -318,13 +319,10 @@ ip6_tnl_dev_uninit(struct net_device *dev)
         struct net *net = dev_net(dev);
         struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
 
-        if (dev == ip6n->fb_tnl_dev) {
-                spin_lock_bh(&ip6_tnl_lock);
-                ip6n->tnls_wc[0] = NULL;
-                spin_unlock_bh(&ip6_tnl_lock);
-        } else {
+        if (dev == ip6n->fb_tnl_dev)
+                rcu_assign_pointer(ip6n->tnls_wc[0], NULL);
+        else
                 ip6_tnl_unlink(ip6n, t);
-        }
         ip6_tnl_dst_reset(t);
         dev_put(dev);
 }
@@ -1369,7 +1367,7 @@ static void __net_init ip6_fb_tnl_dev_init(struct net_device *dev)
         ip6_tnl_dev_init_gen(dev);
         t->parms.proto = IPPROTO_IPV6;
         dev_hold(dev);
-        ip6n->tnls_wc[0] = t;
+        rcu_assign_pointer(ip6n->tnls_wc[0], t);
 }
 
 static struct xfrm6_tunnel ip4ip6_handler __read_mostly = {
@@ -1391,14 +1389,14 @@ static void __net_exit ip6_tnl_destroy_tunnels(struct ip6_tnl_net *ip6n)
         LIST_HEAD(list);
 
         for (h = 0; h < HASH_SIZE; h++) {
-                t = ip6n->tnls_r_l[h];
+                t = rtnl_dereference(ip6n->tnls_r_l[h]);
                 while (t != NULL) {
                         unregister_netdevice_queue(t->dev, &list);
-                        t = t->next;
+                        t = rtnl_dereference(t->next);
                 }
         }
 
-        t = ip6n->tnls_wc[0];
+        t = rtnl_dereference(ip6n->tnls_wc[0]);
         unregister_netdevice_queue(t->dev, &list);
         unregister_netdevice_many(&list);
 }