mptcp: call mp_fail_no_response only when needed

mptcp_mp_fail_no_response shouldn't be invoked on each worker run, it
should be invoked only when MP_FAIL response timeout occurs.

This patch adds a new msk flag MPTCP_FAIL_RESPONSE_EXPECT, set it when
sending MP_FAIL and test it in mptcp_timeout_timer().

Add back MPTCP_FAIL_NO_RESPONSE flag, set it in mptcp_timeout_timer()
when MP_FAIL response timeout occurs. Test it in mptcp_worker() before
invoking mptcp_mp_fail_no_response().

Closes: multipath-tcp/mptcp_net-next#281
Fixes: d9fb797 ("mptcp: Do not traverse the subflow connection list without lock")
Signed-off-by: Geliang Tang <geliang.tang@suse.com>

net/mptcp/protocol.c

@@ -2185,7 +2185,12 @@ mp_fail_response_expect_subflow(struct mptcp_sock *msk)
 static void mptcp_timeout_timer(struct timer_list *t)
 {
 	struct sock *sk = from_timer(sk, t, sk_timer);
+	struct mptcp_sock *msk = mptcp_sk(sk);
 
+	bh_lock_sock(sk);
+	if (test_and_clear_bit(MPTCP_FAIL_RESPONSE_EXPECT, &msk->flags))
+		__set_bit(MPTCP_FAIL_NO_RESPONSE, &msk->flags);
+	bh_unlock_sock(sk);
 	mptcp_schedule_work(sk);
 	sock_put(sk);
 }
@@ -2562,7 +2567,8 @@ static void mptcp_worker(struct work_struct *work)
 	if (test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
 		__mptcp_retrans(sk);
 
-	mptcp_mp_fail_no_response(msk);
+	if (test_and_clear_bit(MPTCP_FAIL_NO_RESPONSE, &msk->flags))
+		mptcp_mp_fail_no_response(msk);
 
 unlock:
 	release_sock(sk);

net/mptcp/protocol.h

@@ -116,6 +116,8 @@
 #define MPTCP_WORK_EOF		3
 #define MPTCP_FALLBACK_DONE	4
 #define MPTCP_WORK_CLOSE_SUBFLOW 5
+#define MPTCP_FAIL_RESPONSE_EXPECT	6
+#define MPTCP_FAIL_NO_RESPONSE		7
 
 /* MPTCP socket release cb flags */
 #define MPTCP_PUSH_PENDING	1

net/mptcp/subflow.c

@@ -1240,6 +1240,7 @@ static bool subflow_check_data_avail(struct sock *ssk)
 					sk_eat_skb(ssk, skb);
 			} else if (!sock_flag(ssk, SOCK_DEAD)) {
 				WRITE_ONCE(subflow->mp_fail_response_expect, true);
+				__set_bit(MPTCP_FAIL_RESPONSE_EXPECT, &msk->flags);
 				sk_reset_timer((struct sock *)msk,
 					       &((struct sock *)msk)->sk_timer,
 					       jiffies + TCP_RTO_MAX);