decnet: RCU conversion and get rid of dev_base_lock

While tracking dev_base_lock users, I found decnet used it in
dnet_select_source(), but for a wrong purpose:

Writers only hold RTNL, not dev_base_lock, so readers must use RCU if
they cannot use RTNL.

Adds an rcu_head in struct dn_ifaddr and handle proper RCU management.

Adds __rcu annotation in dn_route as well.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 9 deletions

diff --git a/include/net/dn_dev.h b/include/net/dn_dev.h
index 0916bbf3bdff..b9e32db03f20 100644
--- a/include/net/dn_dev.h
+++ b/include/net/dn_dev.h
@@ -5,13 +5,14 @@
 struct dn_dev;
 
 struct dn_ifaddr {
-        struct dn_ifaddr *ifa_next;
+        struct dn_ifaddr __rcu *ifa_next;
         struct dn_dev    *ifa_dev;
         __le16            ifa_local;
         __le16            ifa_address;
         __u8              ifa_flags;
         __u8              ifa_scope;
         char              ifa_label[IFNAMSIZ];
+        struct rcu_head   rcu;
 };
 
 #define DN_DEV_S_RU  0 /* Run - working normally   */
@@ -83,7 +84,7 @@ struct dn_dev_parms {
 
 
 struct dn_dev {
-        struct dn_ifaddr *ifa_list;
+        struct dn_ifaddr __rcu *ifa_list;
         struct net_device *dev;
         struct dn_dev_parms parms;
         char use_long;
@@ -171,19 +172,27 @@ extern int unregister_dnaddr_notifier(struct notifier_block *nb);
 
 static inline int dn_dev_islocal(struct net_device *dev, __le16 addr)
 {
-        struct dn_dev *dn_db = dev->dn_ptr;
+        struct dn_dev *dn_db;
         struct dn_ifaddr *ifa;
+        int res = 0;
 
+        rcu_read_lock();
+        dn_db = rcu_dereference(dev->dn_ptr);
         if (dn_db == NULL) {
                 printk(KERN_DEBUG "dn_dev_islocal: Called for non DECnet device\n");
-                return 0;
+                goto out;
         }
 
-        for(ifa = dn_db->ifa_list; ifa; ifa = ifa->ifa_next)
-                if ((addr ^ ifa->ifa_local) == 0)
-                        return 1;
-
-        return 0;
+        for (ifa = rcu_dereference(dn_db->ifa_list);
+             ifa != NULL;
+             ifa = rcu_dereference(ifa->ifa_next))
+                if ((addr ^ ifa->ifa_local) == 0) {
+                        res = 1;
+                        break;
+                }
+out:
+        rcu_read_unlock();
+        return res;
 }
 
 #endif /* _NET_DN_DEV_H */