datapath: avoid deferred execution of recirc actions

Port upstream fix to datapath module. The only notable difference
between this patch and the upstream version is that the value of
ovs_recursion_limit (5 for upstream kernel, 4 for out-of-tree
module) is maintained in this patch.

Upstream commit:
    commit f43e6dfb056b58628e43179d8f6b59eae417754d
    Author: Lance Richardson <[email protected]>
    Date:   Mon Sep 12 17:07:23 2016 -0400

    openvswitch: avoid deferred execution of recirc actions

    The ovs kernel data path currently defers the execution of all
    recirc actions until stack utilization is at a minimum.
    This is too limiting for some packet forwarding scenarios due to
    the small size of the deferred action FIFO (10 entries). For
    example, broadcast traffic sent out more than 10 ports with
    recirculation results in packet drops when the deferred action
    FIFO becomes full, as reported here:

         http://openvswitch.org/pipermail/dev/2016-March/067672.html

    Since the current recursion depth is available (it is already tracked
    by the exec_actions_level pcpu variable), we can use it to determine
    whether to execute recirculation actions immediately (safe when
    recursion depth is low) or defer execution until more stack space is
    available.

    With this change, the deferred action fifo size becomes a non-issue
    for currently failing scenarios because it is no longer used when
    there are three or fewer recursions through ovs_execute_actions().

    Suggested-by: Pravin Shelar <[email protected]>

Signed-off-by: Lance Richardson <[email protected]>
Acked-by: Pravin B Shelar <[email protected]>

datapath/actions.c

@@ -70,15 +70,21 @@ struct ovs_frag_data {
 static DEFINE_PER_CPU(struct ovs_frag_data, ovs_frag_data_storage);
 
 #define DEFERRED_ACTION_FIFO_SIZE 10
+#define OVS_RECURSION_LIMIT 4
+#define OVS_DEFERRED_ACTION_THRESHOLD (OVS_RECURSION_LIMIT - 2)
 struct action_fifo {
 	int head;
 	int tail;
 	/* Deferred action fifo queue storage. */
 	struct deferred_action fifo[DEFERRED_ACTION_FIFO_SIZE];
 };
 
-static struct action_fifo __percpu *action_fifos;
+struct recirc_keys {
+	struct sw_flow_key key[OVS_DEFERRED_ACTION_THRESHOLD];
+};
 
+static struct action_fifo __percpu *action_fifos;
+static struct recirc_keys __percpu *recirc_keys;
 static DEFINE_PER_CPU(int, exec_actions_level);
 
 static void action_fifo_init(struct action_fifo *fifo)
@@ -1017,6 +1023,7 @@ static int execute_recirc(struct datapath *dp, struct sk_buff *skb,
 			  const struct nlattr *a, int rem)
 {
 	struct deferred_action *da;
+	int level;
 
 	if (!is_flow_key_valid(key)) {
 		int err;
@@ -1040,6 +1047,18 @@ static int execute_recirc(struct datapath *dp, struct sk_buff *skb,
 			return 0;
 	}
 
+	level = this_cpu_read(exec_actions_level);
+	if (level <= OVS_DEFERRED_ACTION_THRESHOLD) {
+		struct recirc_keys *rks = this_cpu_ptr(recirc_keys);
+		struct sw_flow_key *recirc_key = &rks->key[level - 1];
+
+		*recirc_key = *key;
+		recirc_key->recirc_id = nla_get_u32(a);
+		ovs_dp_process_packet(skb, recirc_key);
+
+		return 0;
+	}
+
 	da = add_deferred_actions(skb, key, NULL);
 	if (da) {
 		da->pkt_key.recirc_id = nla_get_u32(a);
@@ -1206,11 +1225,10 @@ int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb,
 			const struct sw_flow_actions *acts,
 			struct sw_flow_key *key)
 {
-	static const int ovs_recursion_limit = 4;
 	int err, level;
 
 	level = __this_cpu_inc_return(exec_actions_level);
-	if (unlikely(level > ovs_recursion_limit)) {
+	if (unlikely(level > OVS_RECURSION_LIMIT)) {
 		net_crit_ratelimited("ovs: recursion limit reached on datapath %s, probable configuration error\n",
 				     ovs_dp_name(dp));
 		kfree_skb(skb);
@@ -1235,10 +1253,17 @@ int action_fifos_init(void)
 	if (!action_fifos)
 		return -ENOMEM;
 
+	recirc_keys = alloc_percpu(struct recirc_keys);
+	if (!recirc_keys) {
+		free_percpu(action_fifos);
+		return -ENOMEM;
+	}
+
 	return 0;
 }
 
 void action_fifos_exit(void)
 {
 	free_percpu(action_fifos);
+	free_percpu(recirc_keys);
 }