mptcp: use delegate action to schedule 3rd ack retrans

Scheduling a delack in mptcp_established_options_mp() is
not a good idea: such function is called by tcp_send_ack() and
the pending delayed ack will be cleared shortly after by the
tcp_event_ack_sent() call in __tcp_transmit_skb().

Instead use the mptcp delegated action infrastructure to
schedule the delayed ack after the current bh processing completes.

Additionally moves the schedule_3rdack_retransmission() helper
into protocol.c to avoid making it visible in a different compilation
unit.

Fixes: ec3edaa7ca6ce02f ("mptcp: Add handling of outgoing MP_JOIN requests")
Reviewed-by: Mat Martineau <mathew.j.martineau>@linux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 8 deletions

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 67a61ac48b20..d87cc040352e 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -387,6 +387,7 @@ struct mptcp_delegated_action {
 DECLARE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions);
 
 #define MPTCP_DELEGATE_SEND		0
+#define MPTCP_DELEGATE_ACK		1
 
 /* MPTCP subflow context */
 struct mptcp_subflow_context {
@@ -492,23 +493,23 @@ static inline void mptcp_add_pending_subflow(struct mptcp_sock *msk,
 
 void mptcp_subflow_process_delegated(struct sock *ssk);
 
-static inline void mptcp_subflow_delegate(struct mptcp_subflow_context *subflow)
+static inline void mptcp_subflow_delegate(struct mptcp_subflow_context *subflow, int action)
 {
 	struct mptcp_delegated_action *delegated;
 	bool schedule;
 
+	/* the caller held the subflow bh socket lock */
+	lockdep_assert_in_softirq();
+
 	/* The implied barrier pairs with mptcp_subflow_delegated_done(), and
 	 * ensures the below list check sees list updates done prior to status
 	 * bit changes
 	 */
-	if (!test_and_set_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status)) {
+	if (!test_and_set_bit(action, &subflow->delegated_status)) {
 		/* still on delegated list from previous scheduling */
 		if (!list_empty(&subflow->delegated_node))
 			return;
 
-		/* the caller held the subflow bh socket lock */
-		lockdep_assert_in_softirq();
-
 		delegated = this_cpu_ptr(&mptcp_delegated_actions);
 		schedule = list_empty(&delegated->head);
 		list_add_tail(&subflow->delegated_node, &delegated->head);
@@ -533,16 +534,16 @@ mptcp_subflow_delegated_next(struct mptcp_delegated_action *delegated)
 
 static inline bool mptcp_subflow_has_delegated_action(const struct mptcp_subflow_context *subflow)
 {
-	return test_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status);
+	return !!READ_ONCE(subflow->delegated_status);
 }
 
-static inline void mptcp_subflow_delegated_done(struct mptcp_subflow_context *subflow)
+static inline void mptcp_subflow_delegated_done(struct mptcp_subflow_context *subflow, int action)
 {
 	/* pairs with mptcp_subflow_delegate, ensures delegate_node is updated before
 	 * touching the status bit
 	 */
 	smp_wmb();
-	clear_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status);
+	clear_bit(action, &subflow->delegated_status);
 }
 
 int mptcp_is_enabled(const struct net *net);