From: Willem de Bruijn <[email protected]> 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 <[email protected]> Signed-off-by: Willem de Bruijn <[email protected]> --- 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 44102484a76f..947348872c3e 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 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 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); -- 2.15.1.620.gb9897f4670-goog
