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Subject[RFC,net-next v2 8/8] net: tcp: Support MSG_NTCOPY
Date
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@fastly.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
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