linux-kernel - [RFC,net-next v2 8/8] net: tcp: Support MSG

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Date:   Sun, 12 Jun 2022 01:57:57 -0700
From:   Joe Damato <jdamato@...tly.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Joe Damato <jdamato@...tly.com>
Subject: [RFC,net-next v2 8/8] net: tcp: Support MSG_NTCOPY

Support non-temporal copies in the TCP sendmsg path. Previously, the only
way to enable non-temporal copies was to enable them for the entire
interface (via ethtool).

This change allows user programs to request non-temporal copies for
specific sendmsg calls.

Signed-off-by: Joe Damato <jdamato@...tly.com>
---
 include/net/sock.h | 2 +-
 net/ipv4/tcp.c     | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 0063e84..b666ecd 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2200,7 +2200,7 @@ static inline int skb_do_copy_data_nocache(struct sock *sk, struct sk_buff *skb,
 		if (!csum_and_copy_from_iter_full(to, copy, &csum, from))
 			return -EFAULT;
 		skb->csum = csum_block_add(skb->csum, csum, offset);
-	} else if (sk->sk_route_caps & NETIF_F_NOCACHE_COPY) {
+	} else if (sk->sk_route_caps & NETIF_F_NOCACHE_COPY || iov_iter_copy_is_nt(from)) {
 		if (!copy_from_iter_full_nocache(to, copy, from))
 			return -EFAULT;
 	} else if (!copy_from_iter_full(to, copy, from))
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 14ebb4e..5b36e00 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1201,6 +1201,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 
 	flags = msg->msg_flags;
 
+	msg_set_iter_copy_type(msg);
+
 	if (flags & MSG_ZEROCOPY && size && sock_flag(sk, SOCK_ZEROCOPY)) {
 		skb = tcp_write_queue_tail(sk);
 		uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
-- 
2.7.4