[PATCH net-next 4/4] tcp: do not allocate linear memory for zerocopy skbs

[Willem de Bruijn]

From: Willem de Bruijn <will...@google.com>

Zerocopy payload is now always stored in frags, and space for headers
is reversed, so this memory is unused.

Signed-off-by: Willem de Bruijn <will...@google.com>
---
 net/ipv4/tcp.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 947348872c3e..7ac583a2b9fe 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1104,12 +1104,15 @@ static int linear_payload_sz(bool first_skb)
        return 0;
 }
 
-static int select_size(const struct sock *sk, bool sg, bool first_skb)
+static int select_size(const struct sock *sk, bool sg, bool first_skb, bool zc)
 {
        const struct tcp_sock *tp = tcp_sk(sk);
        int tmp = tp->mss_cache;
 
        if (sg) {
+               if (zc)
+                       return 0;
+
                if (sk_can_gso(sk)) {
                        tmp = linear_payload_sz(first_skb);
                } else {
@@ -1282,6 +1285,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr 
*msg, size_t size)
 
                if (copy <= 0 || !tcp_skb_can_collapse_to(skb)) {
                        bool first_skb;
+                       int linear;
 
 new_segment:
                        /* Allocate new segment. If the interface is SG,
@@ -1295,9 +1299,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr 
*msg, size_t size)
                                goto restart;
                        }
                        first_skb = tcp_rtx_and_write_queues_empty(sk);
-                       skb = sk_stream_alloc_skb(sk,
-                                                 select_size(sk, sg, 
first_skb),
-                                                 sk->sk_allocation,
+                       linear = select_size(sk, sg, first_skb, zc);
+                       skb = sk_stream_alloc_skb(sk, linear, sk->sk_allocation,
                                                  first_skb);
                        if (!skb)
                                goto wait_for_memory;
-- 
2.15.1.620.gb9897f4670-goog