openvswitch: Use RCU lock for flow dump operation.

Flow dump operation is read-only operation.  There is no need to
take ovs-lock.  Following patch use rcu-lock for dumping flows.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>

1 files changed, 9 insertions, 8 deletions

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index f2ed7600084e..e6fb866e4ed4 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1104,7 +1104,6 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,
                                   u32 seq, u32 flags, u8 cmd)
 {
         const int skb_orig_len = skb->len;
-        const struct sw_flow_actions *sf_acts;
         struct nlattr *start;
         struct ovs_flow_stats stats;
         struct ovs_header *ovs_header;
@@ -1113,8 +1112,6 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,
         u8 tcp_flags;
         int err;
 
-        sf_acts = ovsl_dereference(flow->sf_acts);
-
         ovs_header = genlmsg_put(skb, portid, seq, &dp_flow_genl_family, flags, cmd);
         if (!ovs_header)
                 return -EMSGSIZE;
@@ -1161,6 +1158,11 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,
          */
         start = nla_nest_start(skb, OVS_FLOW_ATTR_ACTIONS);
         if (start) {
+                const struct sw_flow_actions *sf_acts;
+
+                sf_acts = rcu_dereference_check(flow->sf_acts,
+                                                lockdep_ovsl_is_held());
+
                 err = actions_to_attr(sf_acts->actions, sf_acts->actions_len, skb);
                 if (!err)
                         nla_nest_end(skb, start);
@@ -1440,15 +1442,14 @@ static int ovs_flow_cmd_dump(struct sk_buff *skb, struct netlink_callback *cb)
         struct datapath *dp;
         struct flow_table *table;
 
-        ovs_lock();
+        rcu_read_lock();
         dp = get_dp(sock_net(skb->sk), ovs_header->dp_ifindex);
         if (!dp) {
-                ovs_unlock();
+                rcu_read_unlock();
                 return -ENODEV;
         }
 
-        table = ovsl_dereference(dp->table);
-
+        table = rcu_dereference(dp->table);
         for (;;) {
                 struct sw_flow *flow;
                 u32 bucket, obj;
@@ -1468,7 +1469,7 @@ static int ovs_flow_cmd_dump(struct sk_buff *skb, struct netlink_callback *cb)
                 cb->args[0] = bucket;
                 cb->args[1] = obj;
         }
-        ovs_unlock();
+        rcu_read_unlock();
         return skb->len;
 }