mptcp: clean-up the rtx path

After the previous patch we can easily avoid invoking
the workqueue to perform the retransmission, if the
msk socket lock is held at rtx timer expiration.

This also simplifies the relevant code.

Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 31 deletions

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 1590b9d4cde2..171b77537dcb 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2047,28 +2047,21 @@ out_err:
 	return copied;
 }
 
-static void mptcp_retransmit_handler(struct sock *sk)
-{
-	struct mptcp_sock *msk = mptcp_sk(sk);
-
-	set_bit(MPTCP_WORK_RTX, &msk->flags);
-	mptcp_schedule_work(sk);
-}
-
 static void mptcp_retransmit_timer(struct timer_list *t)
 {
 	struct inet_connection_sock *icsk = from_timer(icsk, t,
 						       icsk_retransmit_timer);
 	struct sock *sk = &icsk->icsk_inet.sk;
+	struct mptcp_sock *msk = mptcp_sk(sk);
 
 	bh_lock_sock(sk);
 	if (!sock_owned_by_user(sk)) {
-		mptcp_retransmit_handler(sk);
+		/* we need a process context to retransmit */
+		if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
+			mptcp_schedule_work(sk);
 	} else {
 		/* delegate our work to tcp_release_cb() */
-		if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED,
-				      &sk->sk_tsq_flags))
-			sock_hold(sk);
+		set_bit(MPTCP_RETRANSMIT, &msk->flags);
 	}
 	bh_unlock_sock(sk);
 	sock_put(sk);
@@ -2958,17 +2951,16 @@ void __mptcp_check_push(struct sock *sk, struct sock *ssk)
 	}
 }
 
-#define MPTCP_DEFERRED_ALL (TCPF_WRITE_TIMER_DEFERRED)
-
 /* processes deferred events and flush wmem */
 static void mptcp_release_cb(struct sock *sk)
 {
-	unsigned long flags, nflags;
-
 	for (;;) {
-		flags = 0;
+		unsigned long flags = 0;
+
 		if (test_and_clear_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->flags))
 			flags |= BIT(MPTCP_PUSH_PENDING);
+		if (test_and_clear_bit(MPTCP_RETRANSMIT, &mptcp_sk(sk)->flags))
+			flags |= BIT(MPTCP_RETRANSMIT);
 		if (!flags)
 			break;
 
@@ -2983,6 +2975,8 @@ static void mptcp_release_cb(struct sock *sk)
 		spin_unlock_bh(&sk->sk_lock.slock);
 		if (flags & BIT(MPTCP_PUSH_PENDING))
 			__mptcp_push_pending(sk, 0);
+		if (flags & BIT(MPTCP_RETRANSMIT))
+			__mptcp_retrans(sk);
 
 		cond_resched();
 		spin_lock_bh(&sk->sk_lock.slock);
@@ -2998,20 +2992,6 @@ static void mptcp_release_cb(struct sock *sk)
 	 */
 	__mptcp_update_wmem(sk);
 	__mptcp_update_rmem(sk);
-
-	do {
-		flags = sk->sk_tsq_flags;
-		if (!(flags & MPTCP_DEFERRED_ALL))
-			return;
-		nflags = flags & ~MPTCP_DEFERRED_ALL;
-	} while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
-
-	sock_release_ownership(sk);
-
-	if (flags & TCPF_WRITE_TIMER_DEFERRED) {
-		mptcp_retransmit_handler(sk);
-		__sock_put(sk);
-	}
 }
 
 void mptcp_subflow_process_delegated(struct sock *ssk)