net: add __must_check to sk_add_backlog

Add the "__must_check" tag to sk_add_backlog() so that any failure to
check and drop packets will be warned about.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -604,7 +604,7 @@ static inline void __sk_add_backlog(struct sock *sk, struct sk_buff *skb)
 }
 
 /* The per-socket spinlock must be held here. */
-static inline int sk_add_backlog(struct sock *sk, struct sk_buff *skb)
+static inline __must_check int sk_add_backlog(struct sock *sk, struct sk_buff *skb)
 {
 	if (sk->sk_backlog.len >= max(sk->sk_backlog.limit, sk->sk_rcvbuf << 1))
 		return -ENOBUFS;