net: introduce lockdep_is_held and update various places to use it

The socket is either locked if we hold the slock spin_lock for
lock_sock_fast and unlock_sock_fast or we own the lock (sk_lock.owned
!= 0). Check for this and at the same time improve that the current
thread/cpu is really holding the lock.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 71bf1de..8ceb3ce 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -868,7 +868,7 @@
 	fl6.fl6_sport = inet->inet_sport;
 	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));
 
-	opt = rcu_dereference_protected(np->opt, sock_owned_by_user(sk));
+	opt = rcu_dereference_protected(np->opt, lockdep_sock_is_held(sk));
 	final_p = fl6_update_dst(&fl6, opt, &final);
 
 	dst = ip6_dst_lookup_flow(sk, &fl6, final_p);