rxrpc: Clean up ACK handling

Clean up the rxrpc_propose_ACK() function.  If deferred PING ACK proposal
is split out, it's only really needed for deferred DELAY ACKs.  All other
ACKs, bar terminal IDLE ACK are sent immediately.  The deferred IDLE ACK
submission can be handled by conversion of a DELAY ACK into an IDLE ACK if
there's nothing to be SACK'd.

Also, because there's a delay between an ACK being generated and being
transmitted, it's possible that other ACKs of the same type will be
generated during that interval.  Apart from the ACK time and the serial
number responded to, most of the ACK body, including window and SACK
parameters, are not filled out till the point of transmission - so we can
avoid generating a new ACK if there's one pending that will cover the SACK
data we need to convey.

Therefore, don't propose a new DELAY or IDLE ACK for a call if there's one
already pending.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

1 files changed, 26 insertions, 69 deletions

diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index 67b54ad914a1..36f60ac1d95d 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -29,70 +29,29 @@ void rxrpc_propose_ping(struct rxrpc_call *call, u32 serial,
 	spin_lock_bh(&call->lock);
 
 	if (time_before(ping_at, call->ping_at)) {
-		rxrpc_inc_stat(call->rxnet, stat_tx_acks[RXRPC_ACK_PING]);
 		WRITE_ONCE(call->ping_at, ping_at);
 		rxrpc_reduce_call_timer(call, ping_at, now,
 					rxrpc_timer_set_for_ping);
-		trace_rxrpc_propose_ack(call, why, RXRPC_ACK_PING, serial,
-					rxrpc_propose_ack_use);
+		trace_rxrpc_propose_ack(call, why, RXRPC_ACK_PING, serial);
 	}
 
 	spin_unlock_bh(&call->lock);
 }
 
 /*
- * propose an ACK be sent
+ * Propose a DELAY ACK be sent in the future.
  */
-static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
-				u32 serial, enum rxrpc_propose_ack_trace why)
+static void __rxrpc_propose_delay_ACK(struct rxrpc_call *call,
+				      rxrpc_serial_t serial,
+				      enum rxrpc_propose_ack_trace why)
 {
-	enum rxrpc_propose_ack_outcome outcome = rxrpc_propose_ack_use;
 	unsigned long expiry = rxrpc_soft_ack_delay;
 	unsigned long now = jiffies, ack_at;
-	s8 prior = rxrpc_ack_priority[ack_reason];
-
-	rxrpc_inc_stat(call->rxnet, stat_tx_acks[ack_reason]);
-
-	/* Update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial
-	 * numbers, but we don't alter the timeout.
-	 */
-	_debug("prior %u %u vs %u %u",
-	       ack_reason, prior,
-	       call->ackr_reason, rxrpc_ack_priority[call->ackr_reason]);
-	if (ack_reason == call->ackr_reason) {
-		if (RXRPC_ACK_UPDATEABLE & (1 << ack_reason)) {
-			outcome = rxrpc_propose_ack_update;
-			call->ackr_serial = serial;
-		}
-	} else if (prior > rxrpc_ack_priority[call->ackr_reason]) {
-		call->ackr_reason = ack_reason;
-		call->ackr_serial = serial;
-	} else {
-		outcome = rxrpc_propose_ack_subsume;
-	}
-
-	switch (ack_reason) {
-	case RXRPC_ACK_REQUESTED:
-		if (rxrpc_requested_ack_delay < expiry)
-			expiry = rxrpc_requested_ack_delay;
-		break;
-
-	case RXRPC_ACK_DELAY:
-		if (rxrpc_soft_ack_delay < expiry)
-			expiry = rxrpc_soft_ack_delay;
-		break;
-
-	case RXRPC_ACK_IDLE:
-		if (rxrpc_idle_ack_delay < expiry)
-			expiry = rxrpc_idle_ack_delay;
-		break;
-
-	default:
-		WARN_ON(1);
-		return;
-	}
 
+	call->ackr_serial = serial;
 
+	if (rxrpc_soft_ack_delay < expiry)
+		expiry = rxrpc_soft_ack_delay;
 	if (call->peer->srtt_us != 0)
 		ack_at = usecs_to_jiffies(call->peer->srtt_us >> 3);
 	else
@@ -100,23 +59,23 @@ static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
 
 	ack_at += READ_ONCE(call->tx_backoff);
 	ack_at += now;
-	if (time_before(ack_at, call->ack_at)) {
-		WRITE_ONCE(call->ack_at, ack_at);
+	if (time_before(ack_at, call->delay_ack_at)) {
+		WRITE_ONCE(call->delay_ack_at, ack_at);
 		rxrpc_reduce_call_timer(call, ack_at, now,
 					rxrpc_timer_set_for_ack);
 	}
 
-	trace_rxrpc_propose_ack(call, why, ack_reason, serial, outcome);
+	trace_rxrpc_propose_ack(call, why, RXRPC_ACK_DELAY, serial);
 }
 
 /*
- * propose an ACK be sent, locking the call structure
+ * Propose a DELAY ACK be sent, locking the call structure
  */
-void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason, u32 serial,
-		       enum rxrpc_propose_ack_trace why)
+void rxrpc_propose_delay_ACK(struct rxrpc_call *call, rxrpc_serial_t  serial,
+			     enum rxrpc_propose_ack_trace why)
 {
 	spin_lock_bh(&call->lock);
-	__rxrpc_propose_ACK(call, ack_reason, serial, why);
+	__rxrpc_propose_delay_ACK(call, serial, why);
 	spin_unlock_bh(&call->lock);
 }
 
@@ -131,6 +90,11 @@ void rxrpc_send_ACK(struct rxrpc_call *call, u8 ack_reason,
 
 	if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
 		return;
+	if (ack_reason == RXRPC_ACK_DELAY &&
+	    test_and_set_bit(RXRPC_CALL_DELAY_ACK_PENDING, &call->flags)) {
+		trace_rxrpc_drop_ack(call, why, ack_reason, serial, false);
+		return;
+	}
 
 	rxrpc_inc_stat(call->rxnet, stat_tx_acks[ack_reason]);
 
@@ -319,7 +283,6 @@ void rxrpc_process_call(struct work_struct *work)
 	unsigned long now, next, t;
 	unsigned int iterations = 0;
 	rxrpc_serial_t ackr_serial;
-	u8 ackr_reason;
 
 	rxrpc_see_call(call);
 
@@ -364,19 +327,13 @@ recheck_state:
 		set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
 	}
 
-	t = READ_ONCE(call->ack_at);
+	t = READ_ONCE(call->delay_ack_at);
 	if (time_after_eq(now, t)) {
 		trace_rxrpc_timer(call, rxrpc_timer_exp_ack, now);
-		cmpxchg(&call->ack_at, t, now + MAX_JIFFY_OFFSET);
-		spin_lock_bh(&call->lock);
-		ackr_reason = call->ackr_reason;
-		ackr_serial = call->ackr_serial;
-		call->ackr_reason = 0;
-		call->ackr_serial = 0;
-		spin_unlock_bh(&call->lock);
-		if (ackr_reason)
-			rxrpc_send_ACK(call, ackr_reason, ackr_serial,
-				       rxrpc_propose_ack_ping_for_lost_ack);
+		cmpxchg(&call->delay_ack_at, t, now + MAX_JIFFY_OFFSET);
+		ackr_serial = xchg(&call->ackr_serial, 0);
+		rxrpc_send_ACK(call, RXRPC_ACK_DELAY, ackr_serial,
+			       rxrpc_propose_ack_ping_for_lost_ack);
 	}
 
 	t = READ_ONCE(call->ack_lost_at);
@@ -441,7 +398,7 @@ recheck_state:
 
 	set(call->expect_req_by);
 	set(call->expect_term_by);
-	set(call->ack_at);
+	set(call->delay_ack_at);
 	set(call->ack_lost_at);
 	set(call->resend_at);
 	set(call->keepalive_at);