From 3efd7ec8dba37dc1609c1ca8e2f01510dd7a291e Mon Sep 17 00:00:00 2001
From: Willem de Bruijn <willemb@google.com>
Date: Fri, 22 Dec 2017 19:00:19 -0500
Subject: [PATCH] tcp: place all zerocopy payload in frags
This avoids an unnecessary copy of 1-2KB and improves tso_fragment,
which has to fall back to tcp_fragment if skb->len != skb_data_len.
It also avoids a surprising inconsistency in notifications:
Zerocopy packets sent over loopback have their frags copied, so set
SO_EE_CODE_ZEROCOPY_COPIED in the notification. But this currently
does not happen for small packets, because when all data fits in the
linear fragment, data is not copied in skb_orphan_frags_rx.
Reported-by: Tom Deseyn <tom.deseyn@gmail.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/ipv4/tcp.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 44102484a76f6..947348872c3e9 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1186,7 +1186,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
int flags, err, copied = 0;
int mss_now = 0, size_goal, copied_syn = 0;
bool process_backlog = false;
- bool sg;
+ bool sg, zc = false;
long timeo;
flags = msg->msg_flags;
@@ -1204,7 +1204,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
goto out_err;
}
- if (!(sk_check_csum_caps(sk) && sk->sk_route_caps & NETIF_F_SG))
+ zc = sk_check_csum_caps(sk) && sk->sk_route_caps & NETIF_F_SG;
+ if (!zc)
uarg->zerocopy = 0;
}
@@ -1325,13 +1326,13 @@ new_segment:
copy = msg_data_left(msg);
/* Where to copy to? */
- if (skb_availroom(skb) > 0) {
+ if (skb_availroom(skb) > 0 && !zc) {
/* We have some space in skb head. Superb! */
copy = min_t(int, copy, skb_availroom(skb));
err = skb_add_data_nocache(sk, skb, &msg->msg_iter, copy);
if (err)
goto do_fault;
- } else if (!uarg || !uarg->zerocopy) {
+ } else if (!zc) {
bool merge = true;
int i = skb_shinfo(skb)->nr_frags;
struct page_frag *pfrag = sk_page_frag(sk);
--
2.39.5