gre: Convert locking to RCU.

Ports commit 8d5b2c "gre: convert hash tables locking to RCU"
from the mainline kernel.

diff --git a/datapath/linux-2.6/compat-2.6/ip_gre.c b/datapath/linux-2.6/compat-2.6/ip_gre.c
index 4c47b92530af17f600dca771efce05e4e0dc61ac..8df5555190639f893f152bd0c69c9ce76d4f340b 100644 (file)
--- a/datapath/linux-2.6/compat-2.6/ip_gre.c
+++ b/datapath/linux-2.6/compat-2.6/ip_gre.c
@@ -178,8 +178,13 @@ struct ipgre_net {
 #define tunnels_r      tunnels[2]
 #define tunnels_l      tunnels[1]
 #define tunnels_wc     tunnels[0]
+/*
+ * Locking : hash tables are protected by RCU and a spinlock
+ */
+static DEFINE_SPINLOCK(ipgre_lock);
 
-static DEFINE_RWLOCK(ipgre_lock);
+#define for_each_ip_tunnel_rcu(start) \
+       for (t = rcu_dereference(start); t; t = rcu_dereference(t->next))
 
 /* Given src, dst and key, find appropriate for input tunnel. */
 
@@ -197,7 +202,7 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
                       ARPHRD_ETHER : ARPHRD_IPGRE;
        int score, cand_score = 4;
 
-       for (t = ign->tunnels_r_l[h0^h1]; t; t = t->next) {
+       for_each_ip_tunnel_rcu(ign->tunnels_r_l[h0 ^ h1]) {
                if (local != t->parms.iph.saddr ||
                    remote != t->parms.iph.daddr ||
                    key != t->parms.i_key ||
@@ -222,7 +227,7 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
                }
        }
 
-       for (t = ign->tunnels_r[h0^h1]; t; t = t->next) {
+       for_each_ip_tunnel_rcu(ign->tunnels_r[h0 ^ h1]) {
                if (remote != t->parms.iph.daddr ||
                    key != t->parms.i_key ||
                    !(t->dev->flags & IFF_UP))
@@ -246,7 +251,7 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
                }
        }
 
-       for (t = ign->tunnels_l[h1]; t; t = t->next) {
+       for_each_ip_tunnel_rcu(ign->tunnels_l[h1]) {
                if ((local != t->parms.iph.saddr &&
                     (local != t->parms.iph.daddr ||
                      !ipv4_is_multicast(local))) ||
@@ -272,7 +277,7 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
                }
        }
 
-       for (t = ign->tunnels_wc[h1]; t; t = t->next) {
+       for_each_ip_tunnel_rcu(ign->tunnels_wc[h1]) {
                if (t->parms.i_key != key ||
                    !(t->dev->flags & IFF_UP))
                        continue;
@@ -298,8 +303,9 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
        if (cand != NULL)
                return cand;
 
-       if (ign->fb_tunnel_dev->flags & IFF_UP)
-               return netdev_priv(ign->fb_tunnel_dev);
+       dev = ign->fb_tunnel_dev;
+       if (dev->flags & IFF_UP)
+               return netdev_priv(dev);
 
        return NULL;
 }
@@ -333,10 +339,10 @@ static void ipgre_tunnel_link(struct ipgre_net *ign, struct ip_tunnel *t)
 {
        struct ip_tunnel **tp = ipgre_bucket(ign, t);
 
+       spin_lock_bh(&ipgre_lock);
        t->next = *tp;
-       write_lock_bh(&ipgre_lock);
-       *tp = t;
-       write_unlock_bh(&ipgre_lock);
+       rcu_assign_pointer(*tp, t);
+       spin_unlock_bh(&ipgre_lock);
 }
 
 static void ipgre_tunnel_unlink(struct ipgre_net *ign, struct ip_tunnel *t)
@@ -345,9 +351,9 @@ static void ipgre_tunnel_unlink(struct ipgre_net *ign, struct ip_tunnel *t)
 
        for (tp = ipgre_bucket(ign, t); *tp; tp = &(*tp)->next) {
                if (t == *tp) {
-                       write_lock_bh(&ipgre_lock);
+                       spin_lock_bh(&ipgre_lock);
                        *tp = t->next;
-                       write_unlock_bh(&ipgre_lock);
+                       spin_unlock_bh(&ipgre_lock);
                        break;
                }
        }
@@ -504,7 +510,7 @@ static void ipgre_err(struct sk_buff *skb, u32 info)
                break;
        }
 
-       read_lock(&ipgre_lock);
+       rcu_read_lock();
        t = ipgre_tunnel_lookup(skb->dev, iph->daddr, iph->saddr,
                                flags & GRE_KEY ?
                                *(((__be32 *)p) + (grehlen / 4) - 1) : 0,
@@ -522,7 +528,7 @@ static void ipgre_err(struct sk_buff *skb, u32 info)
                t->err_count = 1;
        t->err_time = jiffies;
 out:
-       read_unlock(&ipgre_lock);
+       rcu_read_unlock();
        return;
 }
 
@@ -601,7 +607,7 @@ static int ipgre_rcv(struct sk_buff *skb)
 
        gre_proto = *(__be16 *)(h + 2);
 
-       read_lock(&ipgre_lock);
+       rcu_read_lock();
        if ((tunnel = ipgre_tunnel_lookup(skb->dev,
                                          iph->saddr, iph->daddr, key,
                                          gre_proto))) {
@@ -680,13 +686,13 @@ static int ipgre_rcv(struct sk_buff *skb)
                ipgre_ecn_decapsulate(iph, skb);
 
                netif_rx(skb);
-               read_unlock(&ipgre_lock);
+               rcu_read_unlock();
                return(0);
        }
        icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 
 drop:
-       read_unlock(&ipgre_lock);
+       rcu_read_unlock();
 drop_nolock:
        kfree_skb(skb);
        return(0);