netdev - [patch net-next v3 1/7] net: treat possible_net_t net pointer as an RCU one and add read_pnet

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Date: Fri, 13 Oct 2023 14:10:23 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: netdev@...r.kernel.org
Cc: kuba@...nel.org,
	pabeni@...hat.com,
	davem@...emloft.net,
	edumazet@...gle.com
Subject: [patch net-next v3 1/7] net: treat possible_net_t net pointer as an RCU one and add read_pnet_rcu()

From: Jiri Pirko <jiri@...dia.com>

Make the net pointer stored in possible_net_t structure annotated as
an RCU pointer. Change the access helpers to treat it as such.
Introduce read_pnet_rcu() helper to allow caller to dereference
the net pointer under RCU read lock.

Signed-off-by: Jiri Pirko <jiri@...dia.com>
---
v1->v2:
- new patch
---
 include/net/net_namespace.h | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index eb6cd43b1746..13b3a4e29fdb 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -368,21 +368,30 @@ static inline void put_net_track(struct net *net, netns_tracker *tracker)
 
 typedef struct {
 #ifdef CONFIG_NET_NS
-	struct net *net;
+	struct net __rcu *net;
 #endif
 } possible_net_t;
 
 static inline void write_pnet(possible_net_t *pnet, struct net *net)
 {
 #ifdef CONFIG_NET_NS
-	pnet->net = net;
+	rcu_assign_pointer(pnet->net, net);
 #endif
 }
 
 static inline struct net *read_pnet(const possible_net_t *pnet)
 {
 #ifdef CONFIG_NET_NS
-	return pnet->net;
+	return rcu_dereference_protected(pnet->net, true);
+#else
+	return &init_net;
+#endif
+}
+
+static inline struct net *read_pnet_rcu(possible_net_t *pnet)
+{
+#ifdef CONFIG_NET_NS
+	return rcu_dereference(pnet->net);
 #else
 	return &init_net;
 #endif
-- 
2.41.0