mptcp: consolidate sockopt synchronization

Move the socket option synchronization for active subflows
at subflow creation time. This allows removing the now unused
unlocked variant of such helper.

While at that, clean-up a bit the mptcp_subflow_create_socket()
errors path.
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231023-send-net-next-20231023-2-v1-7-9dc60939d371@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/protocol.c

@@ -121,8 +121,6 @@ struct sock *__mptcp_nmpc_sk(struct mptcp_sock *msk)
 		ret = __mptcp_socket_create(msk);
 		if (ret)
 			return ERR_PTR(ret);
-
-		mptcp_sockopt_sync(msk, msk->first);
 	}
 
 	return msk->first;

net/mptcp/sockopt.c

@@ -1444,28 +1444,6 @@ static void sync_socket_options(struct mptcp_sock *msk, struct sock *ssk)
 	inet_assign_bit(FREEBIND, ssk, inet_test_bit(FREEBIND, sk));
 }
 
-static void __mptcp_sockopt_sync(struct mptcp_sock *msk, struct sock *ssk)
-{
-	bool slow = lock_sock_fast(ssk);
-
-	sync_socket_options(msk, ssk);
-
-	unlock_sock_fast(ssk, slow);
-}
-
-void mptcp_sockopt_sync(struct mptcp_sock *msk, struct sock *ssk)
-{
-	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
-
-	msk_owned_by_me(msk);
-
-	if (READ_ONCE(subflow->setsockopt_seq) != msk->setsockopt_seq) {
-		__mptcp_sockopt_sync(msk, ssk);
-
-		subflow->setsockopt_seq = msk->setsockopt_seq;
-	}
-}
-
 void mptcp_sockopt_sync_locked(struct mptcp_sock *msk, struct sock *ssk)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);

net/mptcp/subflow.c

@@ -1533,8 +1533,6 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
 	if (addr.ss_family == AF_INET6)
 		addrlen = sizeof(struct sockaddr_in6);
 #endif
-	mptcp_sockopt_sync(msk, ssk);
-
 	ssk->sk_bound_dev_if = ifindex;
 	err = kernel_bind(sf, (struct sockaddr *)&addr, addrlen);
 	if (err)
@@ -1645,7 +1643,7 @@ int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
 
 	err = security_mptcp_add_subflow(sk, sf->sk);
 	if (err)
-		goto release_ssk;
+		goto err_free;
 
 	/* the newly created socket has to be in the same cgroup as its parent */
 	mptcp_attach_cgroup(sk, sf->sk);
@@ -1659,15 +1657,12 @@ int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
 	get_net_track(net, &sf->sk->ns_tracker, GFP_KERNEL);
 	sock_inuse_add(net, 1);
 	err = tcp_set_ulp(sf->sk, "mptcp");
+	if (err)
+		goto err_free;
 
-release_ssk:
+	mptcp_sockopt_sync_locked(mptcp_sk(sk), sf->sk);
 	release_sock(sf->sk);
 
-	if (err) {
-		sock_release(sf);
-		return err;
-	}
-
 	/* the newly created socket really belongs to the owning MPTCP master
 	 * socket, even if for additional subflows the allocation is performed
 	 * by a kernel workqueue. Adjust inode references, so that the
@@ -1687,6 +1682,11 @@ int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
 	mptcp_subflow_ops_override(sf->sk);
 
 	return 0;
+
+err_free:
+	release_sock(sf->sk);
+	sock_release(sf);
+	return err;
 }
 
 static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,