IPv6: convert addrconf hash list to RCU

Convert from reader/writer lock to RCU and spinlock for addrconf
hash list.

Adds an additional helper macro for hlist_for_each_entry_continue_rcu
to handle the continue case.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 58 insertions, 41 deletions

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 2c9b46cff3d7..004908b104d5 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -428,5 +428,18 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
                 ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
                 pos = rcu_dereference_raw(pos->next))
 
+/**
+ * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point
+ * @tpos:       the type * to use as a loop cursor.
+ * @pos:        the &struct hlist_node to use as a loop cursor.
+ * @member:     the name of the hlist_node within the struct.
+ */
+#define hlist_for_each_entry_continue_rcu(tpos, pos, member)            \
+        for (pos = rcu_dereference((pos)->next);                        \
+             pos && ({ prefetch(pos->next); 1; }) &&                    \
+             ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; });  \
+             pos = rcu_dereference(pos->next))
+
+
 #endif  /* __KERNEL__ */
 #endif
diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 498401541519..22a00b1d2c38 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -64,6 +64,7 @@ struct inet6_ifaddr {
 #endif
 
         int                     dead;
+        struct rcu_head         rcu;
 };
 
 struct ip6_sf_socklist {
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 0488b9f8071d..7ffd5eeab967 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -127,7 +127,7 @@ static int ipv6_count_addresses(struct inet6_dev *idev);
  *      Configured unicast address hash table
  */
 static struct hlist_head inet6_addr_lst[IN6_ADDR_HSIZE];
-static DEFINE_RWLOCK(addrconf_hash_lock);
+static DEFINE_SPINLOCK(addrconf_hash_lock);
 
 static void addrconf_verify(unsigned long);
 
@@ -523,8 +523,13 @@ static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int old)
 }
 #endif
 
-/* Nobody refers to this ifaddr, destroy it */
+static void inet6_ifa_finish_destroy_rcu(struct rcu_head *head)
+{
+        struct inet6_ifaddr *ifp = container_of(head, struct inet6_ifaddr, rcu);
+        kfree(ifp);
+}
 
+/* Nobody refers to this ifaddr, destroy it */
 void inet6_ifa_finish_destroy(struct inet6_ifaddr *ifp)
 {
         WARN_ON(ifp->if_next != NULL);
@@ -545,7 +550,7 @@ void inet6_ifa_finish_destroy(struct inet6_ifaddr *ifp)
         }
         dst_release(&ifp->rt->u.dst);
 
-        kfree(ifp);
+        call_rcu(&ifp->rcu, inet6_ifa_finish_destroy_rcu);
 }
 
 static void
@@ -616,7 +621,7 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr, int pfxlen,
                 goto out2;
         }
 
-        write_lock(&addrconf_hash_lock);
+        spin_lock(&addrconf_hash_lock);
 
         /* Ignore adding duplicate addresses on an interface */
         if (ipv6_chk_same_addr(dev_net(idev->dev), addr, idev->dev)) {
@@ -670,9 +675,9 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr, int pfxlen,
         /* Add to big hash table */
         hash = ipv6_addr_hash(addr);
 
-        hlist_add_head(&ifa->addr_lst, &inet6_addr_lst[hash]);
+        hlist_add_head_rcu(&ifa->addr_lst, &inet6_addr_lst[hash]);
         in6_ifa_hold(ifa);
-        write_unlock(&addrconf_hash_lock);
+        spin_unlock(&addrconf_hash_lock);
 
         write_lock(&idev->lock);
         /* Add to inet6_dev unicast addr list. */
@@ -699,7 +704,7 @@ out2:
 
         return ifa;
 out:
-        write_unlock(&addrconf_hash_lock);
+        spin_unlock(&addrconf_hash_lock);
         goto out2;
 }
 
@@ -717,10 +722,10 @@ static void ipv6_del_addr(struct inet6_ifaddr *ifp)
 
         ifp->dead = 1;
 
-        write_lock_bh(&addrconf_hash_lock);
-        hlist_del_init(&ifp->addr_lst);
+        spin_lock_bh(&addrconf_hash_lock);
+        hlist_del_init_rcu(&ifp->addr_lst);
         __in6_ifa_put(ifp);
-        write_unlock_bh(&addrconf_hash_lock);
+        spin_unlock_bh(&addrconf_hash_lock);
 
         write_lock_bh(&idev->lock);
 #ifdef CONFIG_IPV6_PRIVACY
@@ -1274,8 +1279,8 @@ int ipv6_chk_addr(struct net *net, struct in6_addr *addr,
         struct hlist_node *node;
         u8 hash = ipv6_addr_hash(addr);
 
-        read_lock_bh(&addrconf_hash_lock);
-        hlist_for_each_entry(ifp, node, &inet6_addr_lst[hash], addr_lst) {
+        rcu_read_lock_bh();
+        hlist_for_each_entry_rcu(ifp, node, &inet6_addr_lst[hash], addr_lst) {
                 if (!net_eq(dev_net(ifp->idev->dev), net))
                         continue;
                 if (ipv6_addr_equal(&ifp->addr, addr) &&
@@ -1285,7 +1290,8 @@ int ipv6_chk_addr(struct net *net, struct in6_addr *addr,
                                 break;
                 }
         }
-        read_unlock_bh(&addrconf_hash_lock);
+        rcu_read_unlock_bh();
+
         return ifp != NULL;
 }
 EXPORT_SYMBOL(ipv6_chk_addr);
@@ -1341,8 +1347,8 @@ struct inet6_ifaddr *ipv6_get_ifaddr(struct net *net, const struct in6_addr *add
         struct hlist_node *node;
         u8 hash = ipv6_addr_hash(addr);
 
-        read_lock_bh(&addrconf_hash_lock);
-        hlist_for_each_entry(ifp, node, &inet6_addr_lst[hash], addr_lst) {
+        rcu_read_lock_bh();
+        hlist_for_each_entry_rcu(ifp, node, &inet6_addr_lst[hash], addr_lst) {
                 if (!net_eq(dev_net(ifp->idev->dev), net))
                         continue;
                 if (ipv6_addr_equal(&ifp->addr, addr)) {
@@ -1353,7 +1359,7 @@ struct inet6_ifaddr *ipv6_get_ifaddr(struct net *net, const struct in6_addr *add
                         }
                 }
         }
-        read_unlock_bh(&addrconf_hash_lock);
+        rcu_read_unlock_bh();
 
         return ifp;
 }
@@ -2698,10 +2704,10 @@ static int addrconf_ifdown(struct net_device *dev, int how)
                 write_unlock_bh(&idev->lock);
 
                 /* clear hash table */
-                write_lock_bh(&addrconf_hash_lock);
-                hlist_del_init(&ifa->addr_lst);
+                spin_lock_bh(&addrconf_hash_lock);
+                hlist_del_init_rcu(&ifa->addr_lst);
                 __in6_ifa_put(ifa);
-                write_unlock_bh(&addrconf_hash_lock);
+                spin_unlock_bh(&addrconf_hash_lock);
 
                 __ipv6_ifa_notify(RTM_DELADDR, ifa);
                 atomic_notifier_call_chain(&inet6addr_chain, NETDEV_DOWN, ifa);
@@ -2946,11 +2952,10 @@ static struct inet6_ifaddr *if6_get_first(struct seq_file *seq)
 
         for (state->bucket = 0; state->bucket < IN6_ADDR_HSIZE; ++state->bucket) {
                 struct hlist_node *n;
-                hlist_for_each_entry(ifa, n,
-                                     &inet6_addr_lst[state->bucket], addr_lst) {
+                hlist_for_each_entry_rcu(ifa, n, &inet6_addr_lst[state->bucket],
+                                         addr_lst)
                         if (net_eq(dev_net(ifa->idev->dev), net))
                                 return ifa;
-                }
         }
         return NULL;
 }
@@ -2962,10 +2967,9 @@ static struct inet6_ifaddr *if6_get_next(struct seq_file *seq,
         struct net *net = seq_file_net(seq);
         struct hlist_node *n = &ifa->addr_lst;
 
-        hlist_for_each_entry_continue(ifa, n, addr_lst) {
+        hlist_for_each_entry_continue_rcu(ifa, n, addr_lst)
                 if (net_eq(dev_net(ifa->idev->dev), net))
                         return ifa;
-        }
 
         while (++state->bucket < IN6_ADDR_HSIZE) {
                 hlist_for_each_entry(ifa, n,
@@ -2989,9 +2993,9 @@ static struct inet6_ifaddr *if6_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *if6_seq_start(struct seq_file *seq, loff_t *pos)
-        __acquires(addrconf_hash_lock)
+        __acquires(rcu)
 {
-        read_lock_bh(&addrconf_hash_lock);
+        rcu_read_lock_bh();
         return if6_get_idx(seq, *pos);
 }
 
@@ -3005,9 +3009,9 @@ static void *if6_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void if6_seq_stop(struct seq_file *seq, void *v)
-        __releases(addrconf_hash_lock)
+        __releases(rcu)
 {
-        read_unlock_bh(&addrconf_hash_lock);
+        rcu_read_unlock_bh();
 }
 
 static int if6_seq_show(struct seq_file *seq, void *v)
@@ -3081,8 +3085,8 @@ int ipv6_chk_home_addr(struct net *net, struct in6_addr *addr)
         struct hlist_node *n;
         u8 hash = ipv6_addr_hash(addr);
 
-        read_lock_bh(&addrconf_hash_lock);
-        hlist_for_each_entry(ifp, n, &inet6_addr_lst[hash], addr_lst) {
+        rcu_read_lock_bh();
+        hlist_for_each_entry_rcu(ifp, n, &inet6_addr_lst[hash], addr_lst) {
                 if (!net_eq(dev_net(ifp->idev->dev), net))
                         continue;
                 if (ipv6_addr_equal(&ifp->addr, addr) &&
@@ -3091,7 +3095,7 @@ int ipv6_chk_home_addr(struct net *net, struct in6_addr *addr)
                         break;
                 }
         }
-        read_unlock_bh(&addrconf_hash_lock);
+        rcu_read_unlock_bh();
         return ret;
 }
 #endif
@@ -3107,7 +3111,8 @@ static void addrconf_verify(unsigned long foo)
         unsigned long now, next;
         int i;
 
-        spin_lock_bh(&addrconf_verify_lock);
+        rcu_read_lock_bh();
+        spin_lock(&addrconf_verify_lock);
         now = jiffies;
         next = now + ADDR_CHECK_FREQUENCY;
 
@@ -3116,8 +3121,8 @@ static void addrconf_verify(unsigned long foo)
         for (i=0; i < IN6_ADDR_HSIZE; i++) {
 
 restart:
-                read_lock(&addrconf_hash_lock);
-                hlist_for_each_entry(ifp, node, &inet6_addr_lst[i], addr_lst) {
+                hlist_for_each_entry_rcu(ifp, node,
+                                         &inet6_addr_lst[i], addr_lst) {
                         unsigned long age;
 #ifdef CONFIG_IPV6_PRIVACY
                         unsigned long regen_advance;
@@ -3139,7 +3144,6 @@ restart:
                             age >= ifp->valid_lft) {
                                 spin_unlock(&ifp->lock);
                                 in6_ifa_hold(ifp);
-                                read_unlock(&addrconf_hash_lock);
                                 ipv6_del_addr(ifp);
                                 goto restart;
                         } else if (ifp->prefered_lft == INFINITY_LIFE_TIME) {
@@ -3161,7 +3165,6 @@ restart:
 
                                 if (deprecate) {
                                         in6_ifa_hold(ifp);
-                                        read_unlock(&addrconf_hash_lock);
 
                                         ipv6_ifa_notify(0, ifp);
                                         in6_ifa_put(ifp);
@@ -3179,7 +3182,7 @@ restart:
                                                 in6_ifa_hold(ifp);
                                                 in6_ifa_hold(ifpub);
                                                 spin_unlock(&ifp->lock);
-                                                read_unlock(&addrconf_hash_lock);
+
                                                 spin_lock(&ifpub->lock);
                                                 ifpub->regen_count = 0;
                                                 spin_unlock(&ifpub->lock);
@@ -3199,12 +3202,12 @@ restart:
                                 spin_unlock(&ifp->lock);
                         }
                 }
-                read_unlock(&addrconf_hash_lock);
         }
 
         addr_chk_timer.expires = time_before(next, jiffies + HZ) ? jiffies + HZ : next;
         add_timer(&addr_chk_timer);
-        spin_unlock_bh(&addrconf_verify_lock);
+        spin_unlock(&addrconf_verify_lock);
+        rcu_read_unlock_bh();
 }
 
 static struct in6_addr *extract_addr(struct nlattr *addr, struct nlattr *local)
@@ -4621,10 +4624,10 @@ void addrconf_cleanup(void)
         /*
          *      Check hash table.
          */
-        write_lock_bh(&addrconf_hash_lock);
+        spin_lock_bh(&addrconf_hash_lock);
         for (i = 0; i < IN6_ADDR_HSIZE; i++)
                 WARN_ON(!hlist_empty(&inet6_addr_lst[i]));
-        write_unlock_bh(&addrconf_hash_lock);
+        spin_unlock_bh(&addrconf_hash_lock);
 
         del_timer(&addr_chk_timer);
         rtnl_unlock();