tcp: place all zerocopy payload in frags (02583ade) · Commits · 戴 / test

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

+5 −4

Original line number	Diff line number	Diff line
		@@ -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);

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