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_WORK_TIMEOUT, set it in
mptcp_timeout_timer(). And test it in mptcp_worker() before invoking
mptcp_mp_fail_no_response().

Check the SOCK_DEAD flag on the subflow in mptcp_mp_fail_no_response()
to make sure it's a MP_FAIL timeout, not a MPTCP socket close timeout.

Now mp_fail_response_expect_subflow() helper is only used by
mptcp_mp_fail_no_response(), move the definition of the helper right
before 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

@@ -2167,25 +2167,13 @@ static void mptcp_retransmit_timer(struct timer_list *t)
 	sock_put(sk);
 }
 
-static struct mptcp_subflow_context *
-mp_fail_response_expect_subflow(struct mptcp_sock *msk)
-{
-	struct mptcp_subflow_context *subflow, *ret = NULL;
-
-	mptcp_for_each_subflow(msk, subflow) {
-		if (READ_ONCE(subflow->mp_fail_response_expect)) {
-			ret = subflow;
-			break;
-		}
-	}
-
-	return ret;
-}
-
 static void mptcp_timeout_timer(struct timer_list *t)
 {
 	struct sock *sk = from_timer(sk, t, sk_timer);
 
+	bh_lock_sock(sk);
+	__set_bit(MPTCP_WORK_TIMEOUT, &mptcp_sk(sk)->flags);
+	bh_unlock_sock(sk);
 	mptcp_schedule_work(sk);
 	sock_put(sk);
 }
@@ -2505,6 +2493,21 @@ static void __mptcp_retrans(struct sock *sk)
 		mptcp_reset_timer(sk);
 }
 
+static struct mptcp_subflow_context *
+mp_fail_response_expect_subflow(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow, *ret = NULL;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->mp_fail_response_expect)) {
+			ret = subflow;
+			break;
+		}
+	}
+
+	return ret;
+}
+
 static void mptcp_mp_fail_no_response(struct mptcp_sock *msk)
 {
 	struct mptcp_subflow_context *subflow;
@@ -2513,9 +2516,12 @@ static void mptcp_mp_fail_no_response(struct mptcp_sock *msk)
 
 	subflow = mp_fail_response_expect_subflow(msk);
 	if (subflow) {
+		ssk = mptcp_subflow_tcp_sock(subflow);
+		if (sock_flag(ssk, SOCK_DEAD))
+			return;
+
 		pr_debug("MP_FAIL doesn't respond, reset the subflow");
 
-		ssk = mptcp_subflow_tcp_sock(subflow);
 		slow = lock_sock_fast(ssk);
 		mptcp_subflow_reset(ssk);
 		unlock_sock_fast(ssk, slow);
@@ -2562,7 +2568,8 @@ 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_WORK_TIMEOUT, &msk->flags))
+		mptcp_mp_fail_no_response(msk);
 
 unlock:
 	release_sock(sk);

net/mptcp/protocol.h

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