tcp: simplify tcp_current_mss

There's very little need for most of the callsites to get
tp->xmit_goal_size updated. That will cost us divide as is,
so slice the function in two. Also, the only users of the
tp->xmit_goal_size are directly behind tcp_current_mss(),
so there's no need to store that variable into tcp_sock
at all! The drop of xmit_goal_size currently leaves 16-bit
hole and some reorganization would again be necessary to
change that (but I'm aiming to fill that hole with u16
xmit_goal_size_segs to cache the results of the remaining
divide to get that tso on regression).

Bring xmit_goal_size parts into tcp.c

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 34 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 325658039139..c1f259d2d33b 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -921,7 +921,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
          * factor and mss.
          */
         if (tcp_skb_pcount(skb) > 1)
-                tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1));
+                tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk));
 
         return 0;
 }
@@ -982,15 +982,6 @@ void tcp_mtup_init(struct sock *sk)
         icsk->icsk_mtup.probe_size = 0;
 }
 
-/* Bound MSS / TSO packet size with the half of the window */
-static int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
-{
-        if (tp->max_window && pktsize > (tp->max_window >> 1))
-                return max(tp->max_window >> 1, 68U - tp->tcp_header_len);
-        else
-                return pktsize;
-}
-
 /* This function synchronize snd mss to current pmtu/exthdr set.
 
    tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
@@ -1037,22 +1028,17 @@ unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
 /* Compute the current effective MSS, taking SACKs and IP options,
  * and even PMTU discovery events into account.
  */
-unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
+unsigned int tcp_current_mss(struct sock *sk)
 {
         struct tcp_sock *tp = tcp_sk(sk);
         struct dst_entry *dst = __sk_dst_get(sk);
         u32 mss_now;
-        u16 xmit_size_goal;
-        int doing_tso = 0;
         unsigned header_len;
         struct tcp_out_options opts;
         struct tcp_md5sig_key *md5;
 
         mss_now = tp->mss_cache;
 
-        if (large_allowed && sk_can_gso(sk))
-                doing_tso = 1;
-
         if (dst) {
                 u32 mtu = dst_mtu(dst);
                 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
@@ -1070,19 +1056,6 @@ unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
                 mss_now -= delta;
         }
 
-        xmit_size_goal = mss_now;
-
-        if (doing_tso) {
-                xmit_size_goal = ((sk->sk_gso_max_size - 1) -
-                                  inet_csk(sk)->icsk_af_ops->net_header_len -
-                                  inet_csk(sk)->icsk_ext_hdr_len -
-                                  tp->tcp_header_len);
-
-                xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal);
-                xmit_size_goal -= (xmit_size_goal % mss_now);
-        }
-        tp->xmit_size_goal = xmit_size_goal;
-
         return mss_now;
 }
 
@@ -1264,7 +1237,7 @@ int tcp_may_send_now(struct sock *sk)
         struct sk_buff *skb = tcp_send_head(sk);
 
         return (skb &&
-                tcp_snd_test(sk, skb, tcp_current_mss(sk, 1),
+                tcp_snd_test(sk, skb, tcp_current_mss(sk),
                              (tcp_skb_is_last(sk, skb) ?
                               tp->nonagle : TCP_NAGLE_PUSH)));
 }
@@ -1421,7 +1394,7 @@ static int tcp_mtu_probe(struct sock *sk)
                 return -1;
 
         /* Very simple search strategy: just double the MSS. */
-        mss_now = tcp_current_mss(sk, 0);
+        mss_now = tcp_current_mss(sk);
         probe_size = 2 * tp->mss_cache;
         size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
         if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
@@ -1903,7 +1876,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
         if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
                 return -EHOSTUNREACH; /* Routing failure or similar. */
 
-        cur_mss = tcp_current_mss(sk, 0);
+        cur_mss = tcp_current_mss(sk);
 
         /* If receiver has shrunk his window, and skb is out of
          * new window, do not retransmit it. The exception is the
@@ -2111,7 +2084,7 @@ void tcp_send_fin(struct sock *sk)
          * unsent frames.  But be careful about outgoing SACKS
          * and IP options.
          */
-        mss_now = tcp_current_mss(sk, 1);
+        mss_now = tcp_current_mss(sk);
 
         if (tcp_send_head(sk) != NULL) {
                 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN;
@@ -2523,7 +2496,7 @@ int tcp_write_wakeup(struct sock *sk)
         if ((skb = tcp_send_head(sk)) != NULL &&
             before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
                 int err;
-                unsigned int mss = tcp_current_mss(sk, 0);
+                unsigned int mss = tcp_current_mss(sk);
                 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
 
                 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))