openvswitch: Use nested-BH locking for ovs_pcpu_storage

ovs_pcpu_storage is a per-CPU variable and relies on disabled BH for its
locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
this data structure requires explicit locking.
The data structure can be referenced recursive and there is a recursion
counter to avoid too many recursions.

Add a local_lock_t to the data structure and use
local_lock_nested_bh() for locking. Add an owner of the struct which is
the current task and acquire the lock only if the structure is not owned
by the current task.

Cc: Aaron Conole <aconole@redhat.com>
Cc: Eelco Chaudron <echaudro@redhat.com>
Cc: Ilya Maximets <i.maximets@ovn.org>
Cc: dev@openvswitch.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20250512092736.229935-9-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
index a12640792605..4a665c3cfa90 100644
--- a/net/openvswitch/datapath.h
+++ b/net/openvswitch/datapath.h
@@ -173,6 +173,39 @@ struct ovs_net {
 	bool xt_label;
 };
 
+struct deferred_action {
+	struct sk_buff *skb;
+	const struct nlattr *actions;
+	int actions_len;
+
+	/* Store pkt_key clone when creating deferred action. */
+	struct sw_flow_key pkt_key;
+};
+
+#define DEFERRED_ACTION_FIFO_SIZE 10
+#define OVS_RECURSION_LIMIT 5
+#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];
+};
+
+struct action_flow_keys {
+	struct sw_flow_key key[OVS_DEFERRED_ACTION_THRESHOLD];
+};
+
+struct ovs_pcpu_storage {
+	struct action_fifo action_fifos;
+	struct action_flow_keys flow_keys;
+	int exec_level;
+	struct task_struct *owner;
+	local_lock_t bh_lock;
+};
+DECLARE_PER_CPU(struct ovs_pcpu_storage, ovs_pcpu_storage);
+
 /**
  * enum ovs_pkt_hash_types - hash info to include with a packet
  * to send to userspace.