Merge tag 'io_uring-6.1-2022-10-22' of git://git.kernel.dk/linux

Pull io_uring follow-up from Jens Axboe:
 "Currently the zero-copy has automatic fallback to normal transmit, and
  it was decided that it'd be cleaner to return an error instead if the
  socket type doesn't support it.

  Zero-copy does work with UDP and TCP, it's more of a future proofing
  kind of thing (eg for samba)"

* tag 'io_uring-6.1-2022-10-22' of git://git.kernel.dk/linux:
  io_uring/net: fail zc sendmsg when unsupported by socket
  io_uring/net: fail zc send when unsupported by socket
  net: flag sockets supporting msghdr originated zerocopy

Author: torvalds

include/linux/net.h

@@ -41,6 +41,7 @@ struct net;
 #define SOCK_NOSPACE		2
 #define SOCK_PASSCRED		3
 #define SOCK_PASSSEC		4
+#define SOCK_SUPPORT_ZC		5
 
 #ifndef ARCH_HAS_SOCKET_TYPES
 /**

io_uring/net.c

@@ -1056,6 +1056,8 @@ int io_send_zc(struct io_kiocb *req, unsigned int issue_flags)
 	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
 		return -ENOTSOCK;
+	if (!test_bit(SOCK_SUPPORT_ZC, &sock->flags))
+		return -EOPNOTSUPP;
 
 	msg.msg_name = NULL;
 	msg.msg_control = NULL;
@@ -1151,6 +1153,8 @@ int io_sendmsg_zc(struct io_kiocb *req, unsigned int issue_flags)
 	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
 		return -ENOTSOCK;
+	if (!test_bit(SOCK_SUPPORT_ZC, &sock->flags))
+		return -EOPNOTSUPP;
 
 	if (req_has_async_data(req)) {
 		kmsg = req->async_data;

net/ipv4/tcp.c

@@ -457,6 +457,7 @@ void tcp_init_sock(struct sock *sk)
 	WRITE_ONCE(sk->sk_sndbuf, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[1]));
 	WRITE_ONCE(sk->sk_rcvbuf, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[1]));
 
+	set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
 	sk_sockets_allocated_inc(sk);
 }
 EXPORT_SYMBOL(tcp_init_sock);

net/ipv4/udp.c

@@ -1624,6 +1624,7 @@ int udp_init_sock(struct sock *sk)
 {
 	skb_queue_head_init(&udp_sk(sk)->reader_queue);
 	sk->sk_destruct = udp_destruct_sock;
+	set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
 	return 0;
 }