ipip: convert hash tables locking to RCU
authorEric Dumazet <eric.dumazet@gmail.com>
Fri, 23 Oct 2009 05:42:02 +0000 (05:42 +0000)
committerDavid S. Miller <davem@davemloft.net>
Sat, 24 Oct 2009 13:07:57 +0000 (06:07 -0700)
IPIP tunnels use one rwlock to protect their hash tables.

This locking scheme can be converted to RCU for free, since netdevice
already must wait for a RCU grace period at dismantle time.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv4/ipip.c

index 6a5539236ab37bac6938e9a9fa4ea85de15ce3ba..3bd69988bccfa1dda40aaa15e487d3763a231f0d 100644 (file)
@@ -134,7 +134,13 @@ static void ipip_fb_tunnel_init(struct net_device *dev);
 static void ipip_tunnel_init(struct net_device *dev);
 static void ipip_tunnel_setup(struct net_device *dev);
 
-static DEFINE_RWLOCK(ipip_lock);
+/*
+ * Locking : hash tables are protected by RCU and a spinlock
+ */
+static DEFINE_SPINLOCK(ipip_lock);
+
+#define for_each_ip_tunnel_rcu(start) \
+       for (t = rcu_dereference(start); t; t = rcu_dereference(t->next))
 
 static struct ip_tunnel * ipip_tunnel_lookup(struct net *net,
                __be32 remote, __be32 local)
@@ -144,20 +150,21 @@ static struct ip_tunnel * ipip_tunnel_lookup(struct net *net,
        struct ip_tunnel *t;
        struct ipip_net *ipn = net_generic(net, ipip_net_id);
 
-       for (t = ipn->tunnels_r_l[h0^h1]; t; t = t->next) {
+       for_each_ip_tunnel_rcu(ipn->tunnels_r_l[h0 ^ h1])
                if (local == t->parms.iph.saddr &&
                    remote == t->parms.iph.daddr && (t->dev->flags&IFF_UP))
                        return t;
-       }
-       for (t = ipn->tunnels_r[h0]; t; t = t->next) {
+
+       for_each_ip_tunnel_rcu(ipn->tunnels_r[h0])
                if (remote == t->parms.iph.daddr && (t->dev->flags&IFF_UP))
                        return t;
-       }
-       for (t = ipn->tunnels_l[h1]; t; t = t->next) {
+
+       for_each_ip_tunnel_rcu(ipn->tunnels_l[h1])
                if (local == t->parms.iph.saddr && (t->dev->flags&IFF_UP))
                        return t;
-       }
-       if ((t = ipn->tunnels_wc[0]) != NULL && (t->dev->flags&IFF_UP))
+
+       t = rcu_dereference(ipn->tunnels_wc[0]);
+       if (t && (t->dev->flags&IFF_UP))
                return t;
        return NULL;
 }
@@ -193,9 +200,9 @@ static void ipip_tunnel_unlink(struct ipip_net *ipn, struct ip_tunnel *t)
 
        for (tp = ipip_bucket(ipn, t); *tp; tp = &(*tp)->next) {
                if (t == *tp) {
-                       write_lock_bh(&ipip_lock);
+                       spin_lock_bh(&ipip_lock);
                        *tp = t->next;
-                       write_unlock_bh(&ipip_lock);
+                       spin_unlock_bh(&ipip_lock);
                        break;
                }
        }
@@ -205,10 +212,10 @@ static void ipip_tunnel_link(struct ipip_net *ipn, struct ip_tunnel *t)
 {
        struct ip_tunnel **tp = ipip_bucket(ipn, t);
 
+       spin_lock_bh(&ipip_lock);
        t->next = *tp;
-       write_lock_bh(&ipip_lock);
-       *tp = t;
-       write_unlock_bh(&ipip_lock);
+       rcu_assign_pointer(*tp, t);
+       spin_unlock_bh(&ipip_lock);
 }
 
 static struct ip_tunnel * ipip_tunnel_locate(struct net *net,
@@ -267,9 +274,9 @@ static void ipip_tunnel_uninit(struct net_device *dev)
        struct ipip_net *ipn = net_generic(net, ipip_net_id);
 
        if (dev == ipn->fb_tunnel_dev) {
-               write_lock_bh(&ipip_lock);
+               spin_lock_bh(&ipip_lock);
                ipn->tunnels_wc[0] = NULL;
-               write_unlock_bh(&ipip_lock);
+               spin_unlock_bh(&ipip_lock);
        } else
                ipip_tunnel_unlink(ipn, netdev_priv(dev));
        dev_put(dev);
@@ -318,7 +325,7 @@ static int ipip_err(struct sk_buff *skb, u32 info)
 
        err = -ENOENT;
 
-       read_lock(&ipip_lock);
+       rcu_read_lock();
        t = ipip_tunnel_lookup(dev_net(skb->dev), iph->daddr, iph->saddr);
        if (t == NULL || t->parms.iph.daddr == 0)
                goto out;
@@ -333,7 +340,7 @@ static int ipip_err(struct sk_buff *skb, u32 info)
                t->err_count = 1;
        t->err_time = jiffies;
 out:
-       read_unlock(&ipip_lock);
+       rcu_read_unlock();
        return err;
 }
 
@@ -351,11 +358,11 @@ static int ipip_rcv(struct sk_buff *skb)
        struct ip_tunnel *tunnel;
        const struct iphdr *iph = ip_hdr(skb);
 
-       read_lock(&ipip_lock);
+       rcu_read_lock();
        if ((tunnel = ipip_tunnel_lookup(dev_net(skb->dev),
                                        iph->saddr, iph->daddr)) != NULL) {
                if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
-                       read_unlock(&ipip_lock);
+                       rcu_read_unlock();
                        kfree_skb(skb);
                        return 0;
                }
@@ -374,10 +381,10 @@ static int ipip_rcv(struct sk_buff *skb)
                nf_reset(skb);
                ipip_ecn_decapsulate(iph, skb);
                netif_rx(skb);
-               read_unlock(&ipip_lock);
+               rcu_read_unlock();
                return 0;
        }
-       read_unlock(&ipip_lock);
+       rcu_read_unlock();
 
        return -1;
 }