tcp: move stats merge to the end of tcp_try_coalesce

This change cleans up the last bits of tcp_try_coalesce so that we only
need one goto which jumps to the end of the function.  The idea is to make
the code more readable by putting things in a linear order so that we start
execution at the top of the function, and end it at the bottom.

I also made a slight tweak to the code for handling frags when we are a
clone.  Instead of making it an if (clone) loop else nr_frags = 0 I changed
the logic so that if (!clone) we just set the number of frags to 0 which
disables the for loop anyway.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 26 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 41fa5df9abbc..84e69e02fe20 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4548,15 +4548,13 @@ static bool tcp_try_coalesce(struct sock *sk,
         int i, delta, len = from->len;
 
         *fragstolen = false;
+
         if (tcp_hdr(from)->fin || skb_cloned(to))
                 return false;
+
         if (len <= skb_tailroom(to)) {
                 BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len));
-merge:
-                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE);
-                TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq;
-                TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq;
-                return true;
+                goto merge;
         }
 
         if (skb_has_frag_list(to) || skb_has_frag_list(from))
@@ -4581,7 +4579,6 @@ merge:
                 skb_fill_page_desc(to, skb_shinfo(to)->nr_frags,
                                    page, offset, skb_headlen(from));
                 *fragstolen = true;
-                goto copyfrags;
         } else {
                 if (skb_shinfo(to)->nr_frags +
                     skb_shinfo(from)->nr_frags > MAX_SKB_FRAGS)
@@ -4589,27 +4586,33 @@ merge:
 
                 delta = from->truesize -
                         SKB_TRUESIZE(skb_end_pointer(from) - from->head);
-copyfrags:
-                WARN_ON_ONCE(delta < len);
-                memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags,
-                       skb_shinfo(from)->frags,
-                       skb_shinfo(from)->nr_frags * sizeof(skb_frag_t));
-                skb_shinfo(to)->nr_frags += skb_shinfo(from)->nr_frags;
-
-                if (skb_cloned(from))
-                        for (i = 0; i < skb_shinfo(from)->nr_frags; i++)
-                                skb_frag_ref(from, i);
-                else
-                        skb_shinfo(from)->nr_frags = 0;
-
-                to->truesize += delta;
-                atomic_add(delta, &sk->sk_rmem_alloc);
-                sk_mem_charge(sk, delta);
-                to->len += len;
-                to->data_len += len;
-                goto merge;
         }
-        return false;
+
+        WARN_ON_ONCE(delta < len);
+
+        memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags,
+               skb_shinfo(from)->frags,
+               skb_shinfo(from)->nr_frags * sizeof(skb_frag_t));
+        skb_shinfo(to)->nr_frags += skb_shinfo(from)->nr_frags;
+
+        if (!skb_cloned(from))
+                skb_shinfo(from)->nr_frags = 0;
+
+        /* if the skb is cloned this does nothing since we set nr_frags to 0 */
+        for (i = 0; i < skb_shinfo(from)->nr_frags; i++)
+                skb_frag_ref(from, i);
+
+        to->truesize += delta;
+        atomic_add(delta, &sk->sk_rmem_alloc);
+        sk_mem_charge(sk, delta);
+        to->len += len;
+        to->data_len += len;
+
+merge:
+        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE);
+        TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq;
+        TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq;
+        return true;
 }
 
 static void kfree_skb_partial(struct sk_buff *skb, bool head_stolen)