tcp: Allow send-limited cwnd to grow up to max_burst when gso disabled

This changes the logic in tcp_is_cwnd_limited() so that cwnd may grow
up to tcp_max_burst() even when sk_can_gso() is false, or when
sysctl_tcp_tso_win_divisor != 0.

Signed-off-by: John Heffner <johnwheffner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_cong.c

@@ -285,14 +285,11 @@ int tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
 	if (in_flight >= tp->snd_cwnd)
 		return 1;
 
-	if (!sk_can_gso(sk))
-		return 0;
-
 	left = tp->snd_cwnd - in_flight;
-	if (sysctl_tcp_tso_win_divisor)
-		return left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd;
-	else
-		return left <= tcp_max_burst(tp);
+	if (sk_can_gso(sk) &&
+	    left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd)
+		return 1;
+	return left <= tcp_max_burst(tp);
 }
 EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited);