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Date: Wed, 11 Oct 2023 13:43:38 +1000
From: Nicholas Piggin <npiggin@...il.com>
To: netdev@...r.kernel.org
Cc: Nicholas Piggin <npiggin@...il.com>,
dev@...nvswitch.org,
Pravin B Shelar <pshelar@....org>,
Aaron Conole <aconole@...hat.com>,
"Eelco Chaudron" <echaudro@...hat.com>,
"Ilya Maximets" <imaximet@...hat.com>,
"Flavio Leitner" <fbl@...hat.com>
Subject: [PATCH 1/7] net: openvswitch: generalise the per-cpu flow key allocation stack
Rather than an implicit key allocation index based on the recursion
level, make this a standalone FIFO allocator. This makes it usable
in other places without modifying the recursion accounting.
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
net/openvswitch/actions.c | 104 ++++++++++++++++++++++++++------------
1 file changed, 72 insertions(+), 32 deletions(-)
diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index fd66014d8a76..bc7a8c2fff91 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -59,9 +59,10 @@ 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 5
-#define OVS_DEFERRED_ACTION_THRESHOLD (OVS_RECURSION_LIMIT - 2)
+#define NR_FLOW_KEYS 5
+#define DEFERRED_ACTION_FIFO_SIZE 10
+
struct action_fifo {
int head;
int tail;
@@ -69,27 +70,64 @@ struct action_fifo {
struct deferred_action fifo[DEFERRED_ACTION_FIFO_SIZE];
};
-struct action_flow_keys {
- struct sw_flow_key key[OVS_DEFERRED_ACTION_THRESHOLD];
+struct flow_key_stack {
+ struct sw_flow_key key[NR_FLOW_KEYS];
};
-static struct action_fifo __percpu *action_fifos;
-static struct action_flow_keys __percpu *flow_keys;
static DEFINE_PER_CPU(int, exec_actions_level);
+static struct flow_key_stack __percpu *flow_key_stack;
+static DEFINE_PER_CPU(int, flow_keys_allocated);
+
+static struct action_fifo __percpu *action_fifos;
+
+/*
+ * ovs_flow_key_alloc provides a per-CPU sw_flow_key allocator. keys must be
+ * freed in the reverse order that they were allocated in (i.e., a stack).
+ */
+static struct sw_flow_key *ovs_flow_key_alloc(void)
+{
+ struct flow_key_stack *keys = this_cpu_ptr(flow_key_stack);
+ int level = this_cpu_read(flow_keys_allocated);
+
+ if (unlikely(level >= NR_FLOW_KEYS))
+ return NULL;
+
+ __this_cpu_inc(flow_keys_allocated);
+
+ return &keys->key[level];
+}
+
+static void ovs_flow_key_free(struct sw_flow_key *key)
+{
+ struct flow_key_stack *keys = this_cpu_ptr(flow_key_stack);
+ int level = this_cpu_read(flow_keys_allocated);
+
+ /*
+ * If these debug checks fire then keys will cease being freed
+ * and the allocator will become exhausted and stop working. This
+ * gives a graceful failure mode for programming errors.
+ */
+
+ if (WARN_ON_ONCE(level == 0))
+ return; /* Underflow */
+
+ if (WARN_ON_ONCE(key != &keys->key[level - 1]))
+ return; /* Mismatched alloc/free order */
+
+ __this_cpu_dec(flow_keys_allocated);
+}
+
/* Make a clone of the 'key', using the pre-allocated percpu 'flow_keys'
* space. Return NULL if out of key spaces.
*/
static struct sw_flow_key *clone_key(const struct sw_flow_key *key_)
{
- struct action_flow_keys *keys = this_cpu_ptr(flow_keys);
- int level = this_cpu_read(exec_actions_level);
- struct sw_flow_key *key = NULL;
+ struct sw_flow_key *key;
- if (level <= OVS_DEFERRED_ACTION_THRESHOLD) {
- key = &keys->key[level - 1];
+ key = ovs_flow_key_alloc();
+ if (likely(key))
*key = *key_;
- }
return key;
}
@@ -1522,9 +1560,10 @@ static int clone_execute(struct datapath *dp, struct sk_buff *skb,
{
struct deferred_action *da;
struct sw_flow_key *clone;
+ int err = 0;
skb = last ? skb : skb_clone(skb, GFP_ATOMIC);
- if (!skb) {
+ if (unlikely(!skb)) {
/* Out of memory, skip this action.
*/
return 0;
@@ -1536,26 +1575,27 @@ static int clone_execute(struct datapath *dp, struct sk_buff *skb,
* 'flow_keys'. If clone is successful, execute the actions
* without deferring.
*/
- clone = clone_flow_key ? clone_key(key) : key;
- if (clone) {
- int err = 0;
+ if (clone_flow_key) {
+ clone = clone_key(key);
+ if (unlikely(!clone))
+ goto defer;
+ } else {
+ clone = key;
+ }
- if (actions) { /* Sample action */
- if (clone_flow_key)
- __this_cpu_inc(exec_actions_level);
+ if (actions) { /* Sample action */
+ err = do_execute_actions(dp, skb, clone, actions, len);
+ } else { /* Recirc action */
+ clone->recirc_id = recirc_id;
+ ovs_dp_process_packet(skb, clone);
+ }
- err = do_execute_actions(dp, skb, clone,
- actions, len);
+ if (clone_flow_key)
+ ovs_flow_key_free(clone);
- if (clone_flow_key)
- __this_cpu_dec(exec_actions_level);
- } else { /* Recirc action */
- clone->recirc_id = recirc_id;
- ovs_dp_process_packet(skb, clone);
- }
- return err;
- }
+ return err;
+defer:
/* Out of 'flow_keys' space. Defer actions */
da = add_deferred_actions(skb, key, actions, len);
if (da) {
@@ -1642,8 +1682,8 @@ int action_fifos_init(void)
if (!action_fifos)
return -ENOMEM;
- flow_keys = alloc_percpu(struct action_flow_keys);
- if (!flow_keys) {
+ flow_key_stack = alloc_percpu(struct flow_key_stack);
+ if (!flow_key_stack) {
free_percpu(action_fifos);
return -ENOMEM;
}
@@ -1654,5 +1694,5 @@ int action_fifos_init(void)
void action_fifos_exit(void)
{
free_percpu(action_fifos);
- free_percpu(flow_keys);
+ free_percpu(flow_key_stack);
}
--
2.42.0
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