mptcp: don't save tcp data_ready and write space callbacks

Assign the helpers directly rather than save/restore in the context
structure.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/protocol.h

@@ -468,9 +468,7 @@ struct mptcp_subflow_context {
 	struct	sock *tcp_sock;	    /* tcp sk backpointer */
 	struct	sock *conn;	    /* parent mptcp_sock */
 	const	struct inet_connection_sock_af_ops *icsk_af_ops;
-	void	(*tcp_data_ready)(struct sock *sk);
 	void	(*tcp_state_change)(struct sock *sk);
-	void	(*tcp_write_space)(struct sock *sk);
 	void	(*tcp_error_report)(struct sock *sk);
 
 	struct	rcu_head rcu;
@@ -614,9 +612,9 @@ bool mptcp_subflow_active(struct mptcp_subflow_context *subflow);
 static inline void mptcp_subflow_tcp_fallback(struct sock *sk,
 					      struct mptcp_subflow_context *ctx)
 {
-	sk->sk_data_ready = ctx->tcp_data_ready;
+	sk->sk_data_ready = sock_def_readable;
 	sk->sk_state_change = ctx->tcp_state_change;
-	sk->sk_write_space = ctx->tcp_write_space;
+	sk->sk_write_space = sk_stream_write_space;
 	sk->sk_error_report = ctx->tcp_error_report;
 
 	inet_csk(sk)->icsk_af_ops = ctx->icsk_af_ops;

net/mptcp/subflow.c

@@ -1654,10 +1654,12 @@ static int subflow_ulp_init(struct sock *sk)
 	tp->is_mptcp = 1;
 	ctx->icsk_af_ops = icsk->icsk_af_ops;
 	icsk->icsk_af_ops = subflow_default_af_ops(sk);
-	ctx->tcp_data_ready = sk->sk_data_ready;
 	ctx->tcp_state_change = sk->sk_state_change;
-	ctx->tcp_write_space = sk->sk_write_space;
 	ctx->tcp_error_report = sk->sk_error_report;
+
+	WARN_ON_ONCE(sk->sk_data_ready != sock_def_readable);
+	WARN_ON_ONCE(sk->sk_write_space != sk_stream_write_space);
+
 	sk->sk_data_ready = subflow_data_ready;
 	sk->sk_write_space = subflow_write_space;
 	sk->sk_state_change = subflow_state_change;
@@ -1712,9 +1714,7 @@ static void subflow_ulp_clone(const struct request_sock *req,
 
 	new_ctx->conn_finished = 1;
 	new_ctx->icsk_af_ops = old_ctx->icsk_af_ops;
-	new_ctx->tcp_data_ready = old_ctx->tcp_data_ready;
 	new_ctx->tcp_state_change = old_ctx->tcp_state_change;
-	new_ctx->tcp_write_space = old_ctx->tcp_write_space;
 	new_ctx->tcp_error_report = old_ctx->tcp_error_report;
 	new_ctx->rel_write_seq = 1;
 	new_ctx->tcp_sock = newsk;