mptcp: add and use mptcp_data_ready helper

allows us to schedule the work queue to drain the ssk receive queue in
a followup patch.

This is needed to avoid sending all-to-pessimistic mptcp-level
acknowledgements.  At this time, the ack_seq is what was last read by
userspace instead of the highest in-sequence number queued for reading.
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/protocol.c

@@ -111,6 +111,14 @@ static struct sock *mptcp_subflow_get(const struct mptcp_sock *msk)
 	return NULL;
 }
 
+void mptcp_data_ready(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	set_bit(MPTCP_DATA_READY, &msk->flags);
+	sk->sk_data_ready(sk);
+}
+
 static bool mptcp_ext_cache_refill(struct mptcp_sock *msk)
 {
 	if (!msk->cached_ext)

net/mptcp/protocol.h

@@ -201,6 +201,7 @@ void mptcp_get_options(const struct sk_buff *skb,
 		       struct tcp_options_received *opt_rx);
 
 void mptcp_finish_connect(struct sock *sk);
+void mptcp_data_ready(struct sock *sk);
 
 int mptcp_token_new_request(struct request_sock *req);
 void mptcp_token_destroy_request(u32 token);

net/mptcp/subflow.c

@@ -554,11 +554,8 @@ static void subflow_data_ready(struct sock *sk)
 		return;
 	}
 
-	if (mptcp_subflow_data_available(sk)) {
-		set_bit(MPTCP_DATA_READY, &mptcp_sk(parent)->flags);
-
-		parent->sk_data_ready(parent);
-	}
+	if (mptcp_subflow_data_available(sk))
+		mptcp_data_ready(parent);
 }
 
 static void subflow_write_space(struct sock *sk)
@@ -690,11 +687,8 @@ static void subflow_state_change(struct sock *sk)
 	 * a fin packet carrying a DSS can be unnoticed if we don't trigger
 	 * the data available machinery here.
 	 */
-	if (parent && subflow->mp_capable && mptcp_subflow_data_available(sk)) {
-		set_bit(MPTCP_DATA_READY, &mptcp_sk(parent)->flags);
-
-		parent->sk_data_ready(parent);
-	}
+	if (parent && subflow->mp_capable && mptcp_subflow_data_available(sk))
+		mptcp_data_ready(parent);
 
 	if (parent && !(parent->sk_shutdown & RCV_SHUTDOWN) &&
 	    !subflow->rx_eof && subflow_is_done(sk)) {