tcp: Remove check in __tcp_push_pending_frames

tcp_push checks tcp_send_head and calls __tcp_push_pending_frames,
which again checks tcp_send_head, and this unnecessary check is
done for every other caller of __tcp_push_pending_frames.

Remove tcp_send_head check in __tcp_push_pending_frames and add
the check to tcp_push_pending_frames. Other functions call
__tcp_push_pending_frames only when tcp_send_head would evaluate
to true.
Signed-off-by: NKrishna Kumar <krkumar2@in.ibm.com>
Acked-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -856,13 +856,6 @@ static inline void tcp_check_probe_timer(struct sock *sk)
 					  icsk->icsk_rto, TCP_RTO_MAX);
 }
 
-static inline void tcp_push_pending_frames(struct sock *sk)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-
-	__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
-}
-
 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
 {
 	tp->snd_wl1 = seq;
@@ -1342,6 +1335,15 @@ static inline int tcp_write_queue_empty(struct sock *sk)
 	return skb_queue_empty(&sk->sk_write_queue);
 }
 
+static inline void tcp_push_pending_frames(struct sock *sk)
+{
+	if (tcp_send_head(sk)) {
+		struct tcp_sock *tp = tcp_sk(sk);
+
+		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
+	}
+}
+
 /* Start sequence of the highest skb with SACKed bit, valid only if
  * sacked > 0 or when the caller has ensured validity by itself.
  */

net/ipv4/tcp_output.c

@@ -1794,11 +1794,6 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
 			       int nonagle)
 {
-	struct sk_buff *skb = tcp_send_head(sk);
-
-	if (!skb)
-		return;
-
 	/* If we are closed, the bytes will have to remain here.
 	 * In time closedown will finish, we empty the write queue and
 	 * all will be happy.