datapath: Refactor get_dp() function into multiple access APIs.

Avoid recursive read_rcu_lock() by using the lighter weight get_dp_rcu()
API. Add proper locking assertions to get_dp().

Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 065356f..94539eb 100644 (file)
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -140,19 +140,29 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *,
 static int queue_userspace_packet(struct datapath *dp, struct sk_buff *,
                                  const struct dp_upcall_info *);
 
-/* Must be called with rcu_read_lock or ovs_mutex. */
-static struct datapath *get_dp(struct net *net, int dp_ifindex)
+/* Must be called with rcu_read_lock. */
+static struct datapath *get_dp_rcu(struct net *net, int dp_ifindex)
 {
-       struct datapath *dp = NULL;
-       struct net_device *dev;
+       struct net_device *dev = dev_get_by_index_rcu(net, dp_ifindex);
 
-       rcu_read_lock();
-       dev = dev_get_by_index_rcu(net, dp_ifindex);
        if (dev) {
                struct vport *vport = ovs_internal_dev_get_vport(dev);
                if (vport)
-                       dp = vport->dp;
+                       return vport->dp;
        }
+
+       return NULL;
+}
+
+/* The caller must hold either ovs_mutex or rcu_read_lock to keep the
+ * returned dp pointer valid. */
+static inline struct datapath *get_dp(struct net *net, int dp_ifindex)
+{
+       struct datapath *dp;
+
+       WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_ovsl_is_held());
+       rcu_read_lock();
+       dp = get_dp_rcu(net, dp_ifindex);
        rcu_read_unlock();
 
        return dp;
@@ -595,7 +605,7 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
        packet->mark = flow->key.phy.skb_mark;
 
        rcu_read_lock();
-       dp = get_dp(sock_net(skb->sk), ovs_header->dp_ifindex);
+       dp = get_dp_rcu(sock_net(skb->sk), ovs_header->dp_ifindex);
        err = -ENODEV;
        if (!dp)
                goto err_unlock;
@@ -1252,7 +1262,7 @@ static int ovs_flow_cmd_dump(struct sk_buff *skb, struct netlink_callback *cb)
        struct datapath *dp;
 
        rcu_read_lock();
-       dp = get_dp(sock_net(skb->sk), ovs_header->dp_ifindex);
+       dp = get_dp_rcu(sock_net(skb->sk), ovs_header->dp_ifindex);
        if (!dp) {
                rcu_read_unlock();
                return -ENODEV;
@@ -2019,7 +2029,7 @@ static int ovs_vport_cmd_dump(struct sk_buff *skb, struct netlink_callback *cb)
        int i, j = 0;
 
        rcu_read_lock();
-       dp = get_dp(sock_net(skb->sk), ovs_header->dp_ifindex);
+       dp = get_dp_rcu(sock_net(skb->sk), ovs_header->dp_ifindex);
        if (!dp) {
                rcu_read_unlock();
                return -ENODEV;