mptcp: use mptcp_schedule_work instead of open-coding it

Beyond reducing code duplication this also avoids scheduling
the mptcp_worker on a closed socket on some edge scenarios.

The addressed issue is actually older than the blamed commit
below, but this fix needs it as a pre-requisite.

Fixes: ba8f48f7 ("mptcp: introduce mptcp_schedule_work")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/options.c

@@ -1192,9 +1192,8 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 	 */
 	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
 		if (mp_opt.data_fin && mp_opt.data_len == 1 &&
-		    mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
-		    schedule_work(&msk->work))
-			sock_hold(subflow->conn);
+		    mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64))
+			mptcp_schedule_work((struct sock *)msk);
 
 		return true;
 	}

net/mptcp/subflow.c

@@ -408,9 +408,8 @@ void mptcp_subflow_reset(struct sock *ssk)
 
 	tcp_send_active_reset(ssk, GFP_ATOMIC);
 	tcp_done(ssk);
-	if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags) &&
-	    schedule_work(&mptcp_sk(sk)->work))
-		return; /* worker will put sk for us */
+	if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags))
+		mptcp_schedule_work(sk);
 
 	sock_put(sk);
 }
@@ -1118,8 +1117,8 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
 				skb_ext_del(skb, SKB_EXT_MPTCP);
 				return MAPPING_OK;
 			} else {
-				if (updated && schedule_work(&msk->work))
-					sock_hold((struct sock *)msk);
+				if (updated)
+					mptcp_schedule_work((struct sock *)msk);
 
 				return MAPPING_DATA_FIN;
 			}
@@ -1222,17 +1221,12 @@ static void mptcp_subflow_discard_data(struct sock *ssk, struct sk_buff *skb,
 /* sched mptcp worker to remove the subflow if no more data is pending */
 static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ssk)
 {
-	struct sock *sk = (struct sock *)msk;
-
 	if (likely(ssk->sk_state != TCP_CLOSE))
 		return;
 
 	if (skb_queue_empty(&ssk->sk_receive_queue) &&
-	    !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags)) {
-		sock_hold(sk);
-		if (!schedule_work(&msk->work))
-			sock_put(sk);
-	}
+	    !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
+		mptcp_schedule_work((struct sock *)msk);
 }
 
 static bool subflow_can_fallback(struct mptcp_subflow_context *subflow)