Merge branch 'tcp-warn-once'

Jason Xing says:

====================
tcp: add tcp_warn_once() common helper

Paolo Abeni suggested we can introduce a new helper to cover more cases
in the future for better debug.
====================

Signed-off-by: David S. Miller <[e-mail]>

include/net/tcp.h

···
 void tcp_plb_check_rehash(struct sock *sk, struct tcp_plb_state *plb);
 void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
 
+static inline void tcp_warn_once(const struct sock *sk, bool cond, const char *str)
+{
+	WARN_ONCE(cond,
+		  "%scwn:%u out:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u advmss:%u mss_cache:%u pmtu:%u\n",
+		  str,
+		  tcp_snd_cwnd(tcp_sk(sk)),
+		  tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
+		  tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
+		  tcp_sk(sk)->tlp_high_seq, sk->sk_state,
+		  inet_csk(sk)->icsk_ca_state,
+		  tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
+		  inet_csk(sk)->icsk_pmtu_cookie);
+}
+
 /* At how many usecs into the future should the RTO fire? */
 static inline s64 tcp_rto_delta_us(const struct sock *sk)
 {
···
 
 		return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
 	} else {
-		WARN_ONCE(1,
-			"rtx queue empty: "
-			"out:%u sacked:%u lost:%u retrans:%u "
-			"tlp_high_seq:%u sk_state:%u ca_state:%u "
-			"advmss:%u mss_cache:%u pmtu:%u\n",
-			tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
-			tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
-			tcp_sk(sk)->tlp_high_seq, sk->sk_state,
-			inet_csk(sk)->icsk_ca_state,
-			tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
-			inet_csk(sk)->icsk_pmtu_cookie);
+		tcp_warn_once(sk, 1, "rtx queue empty: ");
 		return jiffies_to_usecs(rto);
 	}
 

net/ipv4/tcp_output.c

···
 	}
 	skb = skb_rb_last(&sk->tcp_rtx_queue);
 	if (unlikely(!skb)) {
-		WARN_ONCE(tp->packets_out,
-			  "invalid inflight: %u state %u cwnd %u mss %d\n",
-			  tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss);
+		tcp_warn_once(sk, tp->packets_out, "invalid inflight: ");
 		smp_store_release(&inet_csk(sk)->icsk_pending, 0);
 		return;
 	}