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, 35 insertions, 8 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index d3f9beee74c0..886596ff0aae 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -661,6 +661,37 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp)
         return NULL;
 }
 
+static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
+                                       int large_allowed)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        u32 xmit_size_goal;
+
+        xmit_size_goal = mss_now;
+
+        if (large_allowed && sk_can_gso(sk)) {
+                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);
+        }
+
+        return xmit_size_goal;
+}
+
+static int tcp_send_mss(struct sock *sk, int *size_goal, int flags)
+{
+        int mss_now;
+
+        mss_now = tcp_current_mss(sk);
+        *size_goal = tcp_xmit_size_goal(sk, mss_now, !(flags & MSG_OOB));
+
+        return mss_now;
+}
+
 static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffset,
                          size_t psize, int flags)
 {
@@ -677,8 +708,7 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffse
 
         clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
 
-        mss_now = tcp_current_mss(sk, !(flags&MSG_OOB));
-        size_goal = tp->xmit_size_goal;
+        mss_now = tcp_send_mss(sk, &size_goal, flags);
         copied = 0;
 
         err = -EPIPE;
@@ -761,8 +791,7 @@ wait_for_memory:
                 if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
                         goto do_error;
 
-                mss_now = tcp_current_mss(sk, !(flags&MSG_OOB));
-                size_goal = tp->xmit_size_goal;
+                mss_now = tcp_send_mss(sk, &size_goal, flags);
         }
 
 out:
@@ -844,8 +873,7 @@ int tcp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
         /* This should be in poll */
         clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
 
-        mss_now = tcp_current_mss(sk, !(flags&MSG_OOB));
-        size_goal = tp->xmit_size_goal;
+        mss_now = tcp_send_mss(sk, &size_goal, flags);
 
         /* Ok commence sending. */
         iovlen = msg->msg_iovlen;
@@ -1007,8 +1035,7 @@ wait_for_memory:
                         if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
                                 goto do_error;
 
-                        mss_now = tcp_current_mss(sk, !(flags&MSG_OOB));
-                        size_goal = tp->xmit_size_goal;
+                        mss_now = tcp_send_mss(sk, &size_goal, flags);
                 }
         }