gre: get rid of ipgre_lock

As RTNL is held while doing tunnels inserts and deletes, we can remove
ipgre_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, 32 insertions, 29 deletions

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 85176895495a..fc20e687e933 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -129,7 +129,7 @@ static int ipgre_tunnel_bind_dev(struct net_device *dev);
 
 static int ipgre_net_id __read_mostly;
 struct ipgre_net {
-        struct ip_tunnel *tunnels[4][HASH_SIZE];
+        struct ip_tunnel __rcu *tunnels[4][HASH_SIZE];
 
         struct net_device *fb_tunnel_dev;
 };
@@ -159,9 +159,8 @@ struct ipgre_net {
 #define tunnels_l       tunnels[1]
 #define tunnels_wc      tunnels[0]
 /*
- * Locking : hash tables are protected by RCU and a spinlock
+ * Locking : hash tables are protected by RCU and RTNL
  */
-static DEFINE_SPINLOCK(ipgre_lock);
 
 #define for_each_ip_tunnel_rcu(start) \
         for (t = rcu_dereference(start); t; t = rcu_dereference(t->next))
@@ -174,8 +173,8 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
 {
         struct net *net = dev_net(dev);
         int link = dev->ifindex;
-        unsigned h0 = HASH(remote);
-        unsigned h1 = HASH(key);
+        unsigned int h0 = HASH(remote);
+        unsigned int h1 = HASH(key);
         struct ip_tunnel *t, *cand = NULL;
         struct ipgre_net *ign = net_generic(net, ipgre_net_id);
         int dev_type = (gre_proto == htons(ETH_P_TEB)) ?
@@ -290,13 +289,13 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
         return NULL;
 }
 
-static struct ip_tunnel **__ipgre_bucket(struct ipgre_net *ign,
+static struct ip_tunnel __rcu **__ipgre_bucket(struct ipgre_net *ign,
                 struct ip_tunnel_parm *parms)
 {
         __be32 remote = parms->iph.daddr;
         __be32 local = parms->iph.saddr;
         __be32 key = parms->i_key;
-        unsigned h = HASH(key);
+        unsigned int h = HASH(key);
         int prio = 0;
 
         if (local)
@@ -309,7 +308,7 @@ static struct ip_tunnel **__ipgre_bucket(struct ipgre_net *ign,
         return &ign->tunnels[prio][h];
 }
 
-static inline struct ip_tunnel **ipgre_bucket(struct ipgre_net *ign,
+static inline struct ip_tunnel __rcu **ipgre_bucket(struct ipgre_net *ign,
                 struct ip_tunnel *t)
 {
         return __ipgre_bucket(ign, &t->parms);
@@ -317,23 +316,22 @@ static inline struct ip_tunnel **ipgre_bucket(struct ipgre_net *ign,
 
 static void ipgre_tunnel_link(struct ipgre_net *ign, struct ip_tunnel *t)
 {
-        struct ip_tunnel **tp = ipgre_bucket(ign, t);
+        struct ip_tunnel __rcu **tp = ipgre_bucket(ign, t);
 
-        spin_lock_bh(&ipgre_lock);
-        t->next = *tp;
+        rcu_assign_pointer(t->next, rtnl_dereference(*tp));
         rcu_assign_pointer(*tp, t);
-        spin_unlock_bh(&ipgre_lock);
 }
 
 static void ipgre_tunnel_unlink(struct ipgre_net *ign, struct ip_tunnel *t)
 {
-        struct ip_tunnel **tp;
-
-        for (tp = ipgre_bucket(ign, t); *tp; tp = &(*tp)->next) {
-                if (t == *tp) {
-                        spin_lock_bh(&ipgre_lock);
-                        *tp = t->next;
-                        spin_unlock_bh(&ipgre_lock);
+        struct ip_tunnel __rcu **tp;
+        struct ip_tunnel *iter;
+
+        for (tp = ipgre_bucket(ign, t);
+             (iter = rtnl_dereference(*tp)) != NULL;
+             tp = &iter->next) {
+                if (t == iter) {
+                        rcu_assign_pointer(*tp, t->next);
                         break;
                 }
         }
@@ -347,10 +345,13 @@ static struct ip_tunnel *ipgre_tunnel_find(struct net *net,
         __be32 local = parms->iph.saddr;
         __be32 key = parms->i_key;
         int link = parms->link;
-        struct ip_tunnel *t, **tp;
+        struct ip_tunnel *t;
+        struct ip_tunnel __rcu **tp;
         struct ipgre_net *ign = net_generic(net, ipgre_net_id);
 
-        for (tp = __ipgre_bucket(ign, parms); (t = *tp) != NULL; tp = &t->next)
+        for (tp = __ipgre_bucket(ign, parms);
+             (t = rtnl_dereference(*tp)) != NULL;
+             tp = &t->next)
                 if (local == t->parms.iph.saddr &&
                     remote == t->parms.iph.daddr &&
                     key == t->parms.i_key &&
@@ -361,7 +362,7 @@ static struct ip_tunnel *ipgre_tunnel_find(struct net *net,
         return t;
 }
 
-static struct ip_tunnel * ipgre_tunnel_locate(struct net *net,
+static struct ip_tunnel *ipgre_tunnel_locate(struct net *net,
                 struct ip_tunnel_parm *parms, int create)
 {
         struct ip_tunnel *t, *nt;
@@ -669,7 +670,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
         u8     tos;
         __be16 df;
         struct rtable *rt;                      /* Route to the other host */
-        struct net_device *tdev;                        /* Device to other host */
+        struct net_device *tdev;                /* Device to other host */
         struct iphdr  *iph;                     /* Our new IP header */
         unsigned int max_headroom;              /* The extra header space needed */
         int    gre_hlen;
@@ -1013,7 +1014,7 @@ ipgre_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
                                         break;
                                 }
                         } else {
-                                unsigned nflags = 0;
+                                unsigned int nflags = 0;
 
                                 t = netdev_priv(dev);
 
@@ -1126,7 +1127,7 @@ static int ipgre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
 
 static int ipgre_header(struct sk_buff *skb, struct net_device *dev,
                         unsigned short type,
-                        const void *daddr, const void *saddr, unsigned len)
+                        const void *daddr, const void *saddr, unsigned int len)
 {
         struct ip_tunnel *t = netdev_priv(dev);
         struct iphdr *iph = (struct iphdr *)skb_push(skb, t->hlen);
@@ -1275,7 +1276,7 @@ static void ipgre_fb_tunnel_init(struct net_device *dev)
         tunnel->hlen            = sizeof(struct iphdr) + 4;
 
         dev_hold(dev);
-        ign->tunnels_wc[0]      = tunnel;
+        rcu_assign_pointer(ign->tunnels_wc[0], tunnel);
 }
 
 
@@ -1291,11 +1292,13 @@ static void ipgre_destroy_tunnels(struct ipgre_net *ign, struct list_head *head)
         for (prio = 0; prio < 4; prio++) {
                 int h;
                 for (h = 0; h < HASH_SIZE; h++) {
-                        struct ip_tunnel *t = ign->tunnels[prio][h];
+                        struct ip_tunnel *t;
+
+                        t = rtnl_dereference(ign->tunnels[prio][h]);
 
                         while (t != NULL) {
                                 unregister_netdevice_queue(t->dev, head);
-                                t = t->next;
+                                t = rtnl_dereference(t->next);
                         }
                 }
         }
@@ -1522,7 +1525,7 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
                 t = nt;
 
                 if (dev->type != ARPHRD_ETHER) {
-                        unsigned nflags = 0;
+                        unsigned int nflags = 0;
 
                         if (ipv4_is_multicast(p.iph.daddr))
                                 nflags = IFF_BROADCAST;