[RFC net-next v3 12/29] tcp: kill extra io_uring's uarg refcounting

From: Pavel Begunkov
Date: Tue Jun 28 2022 - 15:01:43 EST


io_uring guarantees that passed in uarg stays alive until we return from
sendmsg, so no need to temporarily refcount-pin it in
tcp_sendmsg_locked().

Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
net/ipv4/tcp.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 832c1afcdbe7..3482c934eec8 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1207,7 +1207,6 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)

if (msg->msg_ubuf) {
uarg = msg->msg_ubuf;
- net_zcopy_get(uarg);
zc = sk->sk_route_caps & NETIF_F_SG;
} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
@@ -1437,7 +1436,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
}
out_nopush:
- net_zcopy_put(uarg);
+ if (uarg && !msg->msg_ubuf)
+ net_zcopy_put(uarg);
return copied + copied_syn;

do_error:
@@ -1446,7 +1446,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
if (copied + copied_syn)
goto out;
out_err:
- net_zcopy_put_abort(uarg, true);
+ if (uarg && !msg->msg_ubuf)
+ net_zcopy_put_abort(uarg, true);
err = sk_stream_error(sk, flags, err);
/* make sure we wake any epoll edge trigger waiter */
if (unlikely(tcp_rtx_and_write_queues_empty(sk) && err == -EAGAIN)) {
--
2.36.1