[PATCH v1 net-next 09/12] rtnetlink: Define rtnl_net_trylock().

[Kuniyuki Iwashima <kuniyu@amazon.com>]

We will need the per-netns version of rtnl_trylock().

rtnl_net_trylock() calls __rtnl_net_lock() only when rtnl_trylock()
successfully holds RTNL.

When RTNL is removed, we will use mutex_trylock() for per-netns RTNL.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/rtnetlink.h |  6 ++++++
 net/core/rtnetlink.c      | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 0e62918de63b..14b88f551920 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -101,6 +101,7 @@ void __rtnl_net_lock(struct net *net);
 void __rtnl_net_unlock(struct net *net);
 void rtnl_net_lock(struct net *net);
 void rtnl_net_unlock(struct net *net);
+int rtnl_net_trylock(struct net *net);
 int rtnl_net_lock_cmp_fn(const struct lockdep_map *a, const struct lockdep_map *b);
 
 bool rtnl_net_is_locked(struct net *net);
@@ -132,6 +133,11 @@ static inline void rtnl_net_unlock(struct net *net)
 	rtnl_unlock();
 }
 
+static inline int rtnl_net_trylock(struct net *net)
+{
+	return rtnl_trylock();
+}
+
 static inline void ASSERT_RTNL_NET(struct net *net)
 {
 	ASSERT_RTNL();
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a9c92392fb1d..bb4927da0275 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -210,6 +210,17 @@ void rtnl_net_unlock(struct net *net)
 }
 EXPORT_SYMBOL(rtnl_net_unlock);
 
+int rtnl_net_trylock(struct net *net)
+{
+	int ret = rtnl_trylock();
+
+	if (ret)
+		__rtnl_net_lock(net);
+
+	return ret;
+}
+EXPORT_SYMBOL(rtnl_net_trylock);
+
 static int rtnl_net_cmp_locks(const struct net *net_a, const struct net *net_b)
 {
 	if (net_eq(net_a, net_b))
-- 
2.39.5 (Apple Git-154)