Merge tag 'rxrpc-fixes-20190809' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

David Howells says:

====================
Here's a couple of fixes for rxrpc:

(1) Fix refcounting of the local endpoint.

(2) Don't calculate or report packet skew information. This has been
obsolete since AFS 3.1 and so is a waste of resources.
====================

Signed-off-by: David S. Miller <[e-mail]>

net/rxrpc/af_rxrpc.c

···
 
 service_in_use:
 	write_unlock(&local->services_lock);
-	rxrpc_put_local(local);
+	rxrpc_unuse_local(local);
 	ret = -EADDRINUSE;
 error_unlock:
 	release_sock(&rx->sk);
···
  */
 void rxrpc_kernel_probe_life(struct socket *sock, struct rxrpc_call *call)
 {
-	rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, false,
+	rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, false,
 			  rxrpc_propose_ack_ping_for_check_life);
 	rxrpc_send_ack_packet(call, true, NULL);
 }
···
 	rxrpc_queue_work(&rxnet->service_conn_reaper);
 	rxrpc_queue_work(&rxnet->client_conn_reaper);
 
-	rxrpc_put_local(rx->local);
+	rxrpc_unuse_local(rx->local);
 	rx->local = NULL;
 	key_put(rx->key);
 	rx->key = NULL;

net/rxrpc/ar-internal.h

···
  */
 struct rxrpc_local {
 	struct rcu_head		rcu;
-	atomic_t		usage;
+	atomic_t		active_users;	/* Number of users of the local endpoint */
+	atomic_t		usage;		/* Number of references to the structure */
 	struct rxrpc_net	*rxnet;		/* The network ns in which this resides */
 	struct list_head	link;
 	struct socket		*socket;	/* my UDP socket */
···
 
 	/* receive-phase ACK management */
 	u8			ackr_reason;	/* reason to ACK */
-	u16			ackr_skew;	/* skew on packet being ACK'd */
 	rxrpc_serial_t		ackr_serial;	/* serial of packet being ACK'd */
 	rxrpc_serial_t		ackr_first_seq;	/* first sequence number received */
 	rxrpc_seq_t		ackr_prev_seq;	/* previous sequence number received */
···
 /*
  * call_event.c
  */
-void rxrpc_propose_ACK(struct rxrpc_call *, u8, u16, u32, bool, bool,
+void rxrpc_propose_ACK(struct rxrpc_call *, u8, u32, bool, bool,
 		       enum rxrpc_propose_ack_trace);
 void rxrpc_process_call(struct work_struct *);
 
···
 struct rxrpc_local *rxrpc_get_local(struct rxrpc_local *);
 struct rxrpc_local *rxrpc_get_local_maybe(struct rxrpc_local *);
 void rxrpc_put_local(struct rxrpc_local *);
+struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *);
+void rxrpc_unuse_local(struct rxrpc_local *);
 void rxrpc_queue_local(struct rxrpc_local *);
 void rxrpc_destroy_all_locals(struct rxrpc_net *);
 

net/rxrpc/call_event.c

···
  * propose an ACK be sent
  */
 static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
-				u16 skew, u32 serial, bool immediate,
-				bool background,
+				u32 serial, bool immediate, bool background,
 				enum rxrpc_propose_ack_trace why)
 {
 	enum rxrpc_propose_ack_outcome outcome = rxrpc_propose_ack_use;
···
 		if (RXRPC_ACK_UPDATEABLE & (1 << ack_reason)) {
 			outcome = rxrpc_propose_ack_update;
 			call->ackr_serial = serial;
-			call->ackr_skew = skew;
 		}
 		if (!immediate)
 			goto trace;
 	} else if (prior > rxrpc_ack_priority[call->ackr_reason]) {
 		call->ackr_reason = ack_reason;
 		call->ackr_serial = serial;
-		call->ackr_skew = skew;
 	} else {
 		outcome = rxrpc_propose_ack_subsume;
 	}
···
  * propose an ACK be sent, locking the call structure
  */
 void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
-		       u16 skew, u32 serial, bool immediate, bool background,
+		       u32 serial, bool immediate, bool background,
 		       enum rxrpc_propose_ack_trace why)
 {
 	spin_lock_bh(&call->lock);
-	__rxrpc_propose_ACK(call, ack_reason, skew, serial,
+	__rxrpc_propose_ACK(call, ack_reason, serial,
 			    immediate, background, why);
 	spin_unlock_bh(&call->lock);
 }
···
 		ack_ts = ktime_sub(now, call->acks_latest_ts);
 		if (ktime_to_ns(ack_ts) < call->peer->rtt)
 			goto out;
-		rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, false,
+		rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, false,
 				  rxrpc_propose_ack_ping_for_lost_ack);
 		rxrpc_send_ack_packet(call, true, NULL);
 		goto out;
···
 	if (time_after_eq(now, t)) {
 		trace_rxrpc_timer(call, rxrpc_timer_exp_keepalive, now);
 		cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET);
-		rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, true,
+		rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, true,
 				  rxrpc_propose_ack_ping_for_keepalive);
 		set_bit(RXRPC_CALL_EV_PING, &call->events);
 	}
···
 	send_ack = NULL;
 	if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events)) {
 		call->acks_lost_top = call->tx_top;
-		rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, false,
+		rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, false,
 				  rxrpc_propose_ack_ping_for_lost_ack);
 		send_ack = &call->acks_lost_ping;
 	}

net/rxrpc/input.c

···
  * Ping the other end to fill our RTT cache and to retrieve the rwind
  * and MTU parameters.
  */
-static void rxrpc_send_ping(struct rxrpc_call *call, struct sk_buff *skb,
-			    int skew)
+static void rxrpc_send_ping(struct rxrpc_call *call, struct sk_buff *skb)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	ktime_t now = skb->tstamp;
 
 	if (call->peer->rtt_usage < 3 ||
 	    ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000), now))
-		rxrpc_propose_ACK(call, RXRPC_ACK_PING, skew, sp->hdr.serial,
+		rxrpc_propose_ACK(call, RXRPC_ACK_PING, sp->hdr.serial,
 				  true, true,
 				  rxrpc_propose_ack_ping_for_params);
 }
···
 /*
  * Process a DATA packet, adding the packet to the Rx ring.
  */
-static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb,
-			     u16 skew)
+static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	enum rxrpc_call_state state;
···
 
 ack:
 	if (ack)
-		rxrpc_propose_ACK(call, ack, skew, ack_serial,
+		rxrpc_propose_ACK(call, ack, ack_serial,
 				  immediate_ack, true,
 				  rxrpc_propose_ack_input_data);
 	else
-		rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, skew, serial,
+		rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, serial,
 				  false, true,
 				  rxrpc_propose_ack_input_data);
 
···
  * soft-ACK means that the packet may be discarded and retransmission
  * requested.  A phase is complete when all packets are hard-ACK'd.
  */
-static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb,
-			    u16 skew)
+static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 {
 	struct rxrpc_ack_summary summary = { 0 };
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
···
 	if (buf.ack.reason == RXRPC_ACK_PING) {
 		_proto("Rx ACK %%%u PING Request", sp->hdr.serial);
 		rxrpc_propose_ACK(call, RXRPC_ACK_PING_RESPONSE,
-				  skew, sp->hdr.serial, true, true,
+				  sp->hdr.serial, true, true,
 				  rxrpc_propose_ack_respond_to_ping);
 	} else if (sp->hdr.flags & RXRPC_REQUEST_ACK) {
 		rxrpc_propose_ACK(call, RXRPC_ACK_REQUESTED,
-				  skew, sp->hdr.serial, true, true,
+				  sp->hdr.serial, true, true,
 				  rxrpc_propose_ack_respond_to_ack);
 	}
 
···
 	    RXRPC_TX_ANNO_LAST &&
 	    summary.nr_acks == call->tx_top - hard_ack &&
 	    rxrpc_is_client_call(call))
-		rxrpc_propose_ACK(call, RXRPC_ACK_PING, skew, sp->hdr.serial,
+		rxrpc_propose_ACK(call, RXRPC_ACK_PING, sp->hdr.serial,
 				  false, true,
 				  rxrpc_propose_ack_ping_for_lost_reply);
 
···
  * Process an incoming call packet.
  */
 static void rxrpc_input_call_packet(struct rxrpc_call *call,
-				    struct sk_buff *skb, u16 skew)
+				    struct sk_buff *skb)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	unsigned long timo;
···
 
 	switch (sp->hdr.type) {
 	case RXRPC_PACKET_TYPE_DATA:
-		rxrpc_input_data(call, skb, skew);
+		rxrpc_input_data(call, skb);
 		break;
 
 	case RXRPC_PACKET_TYPE_ACK:
-		rxrpc_input_ack(call, skb, skew);
+		rxrpc_input_ack(call, skb);
 		break;
 
 	case RXRPC_PACKET_TYPE_BUSY:
···
 {
 	_enter("%p,%p", local, skb);
 
-	skb_queue_tail(&local->event_queue, skb);
-	rxrpc_queue_local(local);
+	if (rxrpc_get_local_maybe(local)) {
+		skb_queue_tail(&local->event_queue, skb);
+		rxrpc_queue_local(local);
+	} else {
+		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
+	}
 }
 
 /*
···
 {
 	CHECK_SLAB_OKAY(&local->usage);
 
-	skb_queue_tail(&local->reject_queue, skb);
-	rxrpc_queue_local(local);
+	if (rxrpc_get_local_maybe(local)) {
+		skb_queue_tail(&local->reject_queue, skb);
+		rxrpc_queue_local(local);
+	} else {
+		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
+	}
 }
 
 /*
···
 	struct rxrpc_peer *peer = NULL;
 	struct rxrpc_sock *rx = NULL;
 	unsigned int channel;
-	int skew = 0;
 
 	_enter("%p", udp_sk);
 
···
 			goto out;
 		}
 
-		/* Note the serial number skew here */
-		skew = (int)sp->hdr.serial - (int)conn->hi_serial;
-		if (skew >= 0) {
-			if (skew > 0)
-				conn->hi_serial = sp->hdr.serial;
-		} else {
-			skew = -skew;
-			skew = min(skew, 65535);
-		}
+		if ((int)sp->hdr.serial - (int)conn->hi_serial > 0)
+			conn->hi_serial = sp->hdr.serial;
 
 		/* Call-bound packets are routed by connection channel. */
 		channel = sp->hdr.cid & RXRPC_CHANNELMASK;
···
 		call = rxrpc_new_incoming_call(local, rx, skb);
 		if (!call)
 			goto reject_packet;
-		rxrpc_send_ping(call, skb, skew);
+		rxrpc_send_ping(call, skb);
 		mutex_unlock(&call->user_mutex);
 	}
 
-	rxrpc_input_call_packet(call, skb, skew);
+	rxrpc_input_call_packet(call, skb);
 	goto discard;
 
 discard:

net/rxrpc/local_object.c

···
 	local = kzalloc(sizeof(struct rxrpc_local), GFP_KERNEL);
 	if (local) {
 		atomic_set(&local->usage, 1);
+		atomic_set(&local->active_users, 1);
 		local->rxnet = rxnet;
 		INIT_LIST_HEAD(&local->link);
 		INIT_WORK(&local->processor, rxrpc_local_processor);
···
 		 * bind the transport socket may still fail if we're attempting
 		 * to use a local address that the dying object is still using.
 		 */
-		if (!rxrpc_get_local_maybe(local)) {
-			cursor = cursor->next;
-			list_del_init(&local->link);
+		if (!rxrpc_use_local(local))
 			break;
-		}
 
 		age = "old";
 		goto found;
···
 	if (ret < 0)
 		goto sock_error;
 
-	list_add_tail(&local->link, cursor);
+	if (cursor != &rxnet->local_endpoints)
+		list_replace(cursor, &local->link);
+	else
+		list_add_tail(&local->link, cursor);
 	age = "new";
 
 found:
···
 }
 
 /*
- * Queue a local endpoint.
+ * Queue a local endpoint unless it has become unreferenced and pass the
+ * caller's reference to the work item.
  */
 void rxrpc_queue_local(struct rxrpc_local *local)
 {
···
 	if (rxrpc_queue_work(&local->processor))
 		trace_rxrpc_local(local, rxrpc_local_queued,
 				  atomic_read(&local->usage), here);
-}
-
-/*
- * A local endpoint reached its end of life.
- */
-static void __rxrpc_put_local(struct rxrpc_local *local)
-{
-	_enter("%d", local->debug_id);
-	rxrpc_queue_work(&local->processor);
+	else
+		rxrpc_put_local(local);
 }
 
 /*
···
 		trace_rxrpc_local(local, rxrpc_local_put, n, here);
 
 		if (n == 0)
-			__rxrpc_put_local(local);
+			call_rcu(&local->rcu, rxrpc_local_rcu);
 	}
+}
+
+/*
+ * Start using a local endpoint.
+ */
+struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local)
+{
+	unsigned int au;
+
+	local = rxrpc_get_local_maybe(local);
+	if (!local)
+		return NULL;
+
+	au = atomic_fetch_add_unless(&local->active_users, 1, 0);
+	if (au == 0) {
+		rxrpc_put_local(local);
+		return NULL;
+	}
+
+	return local;
+}
+
+/*
+ * Cease using a local endpoint.  Once the number of active users reaches 0, we
+ * start the closure of the transport in the work processor.
+ */
+void rxrpc_unuse_local(struct rxrpc_local *local)
+{
+	unsigned int au;
+
+	au = atomic_dec_return(&local->active_users);
+	if (au == 0)
+		rxrpc_queue_local(local);
+	else
+		rxrpc_put_local(local);
 }
 
 /*
···
 	struct rxrpc_net *rxnet = local->rxnet;
 
 	_enter("%d", local->debug_id);
-
-	/* We can get a race between an incoming call packet queueing the
-	 * processor again and the work processor starting the destruction
-	 * process which will shut down the UDP socket.
-	 */
-	if (local->dead) {
-		_leave(" [already dead]");
-		return;
-	}
-	local->dead = true;
 
 	mutex_lock(&rxnet->local_mutex);
 	list_del_init(&local->link);
···
 	 */
 	rxrpc_purge_queue(&local->reject_queue);
 	rxrpc_purge_queue(&local->event_queue);
-
-	_debug("rcu local %d", local->debug_id);
-	call_rcu(&local->rcu, rxrpc_local_rcu);
 }
 
 /*
- * Process events on an endpoint
+ * Process events on an endpoint.  The work item carries a ref which
+ * we must release.
  */
 static void rxrpc_local_processor(struct work_struct *work)
 {
···
 
 	do {
 		again = false;
-		if (atomic_read(&local->usage) == 0)
-			return rxrpc_local_destroyer(local);
+		if (atomic_read(&local->active_users) == 0) {
+			rxrpc_local_destroyer(local);
+			break;
+		}
 
 		if (!skb_queue_empty(&local->reject_queue)) {
 			rxrpc_reject_packets(local);
···
 			again = true;
 		}
 	} while (again);
+
+	rxrpc_put_local(local);
 }
 
 /*

net/rxrpc/output.c

···
 	*_top = top;
 
 	pkt->ack.bufferSpace	= htons(8);
-	pkt->ack.maxSkew	= htons(call->ackr_skew);
+	pkt->ack.maxSkew	= htons(0);
 	pkt->ack.firstPacket	= htonl(hard_ack + 1);
 	pkt->ack.previousPacket	= htonl(call->ackr_prev_seq);
 	pkt->ack.serial		= htonl(serial);
···
 			if (ping)
 				clear_bit(RXRPC_CALL_PINGING, &call->flags);
 			rxrpc_propose_ACK(call, pkt->ack.reason,
-					  ntohs(pkt->ack.maxSkew),
 					  ntohl(pkt->ack.serial),
 					  false, true,
 					  rxrpc_propose_ack_retry_tx);

net/rxrpc/recvmsg.c

···
 	ASSERTCMP(call->rx_hard_ack, ==, call->rx_top);
 
 	if (call->state == RXRPC_CALL_CLIENT_RECV_REPLY) {
-		rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, 0, serial, false, true,
+		rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, serial, false, true,
 				  rxrpc_propose_ack_terminal_ack);
 		//rxrpc_send_ack_packet(call, false, NULL);
 	}
···
 		call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
 		call->expect_req_by = jiffies + MAX_JIFFY_OFFSET;
 		write_unlock_bh(&call->state_lock);
-		rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, 0, serial, false, true,
+		rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, serial, false, true,
 				  rxrpc_propose_ack_processing_op);
 		break;
 	default:
···
 		if (after_eq(hard_ack, call->ackr_consumed + 2) ||
 		    after_eq(top, call->ackr_seen + 2) ||
 		    (hard_ack == top && after(hard_ack, call->ackr_consumed)))
-			rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, 0, serial,
+			rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, serial,
 					  true, true,
 					  rxrpc_propose_ack_rotate_rx);
 		if (call->ackr_reason && call->ackr_reason != RXRPC_ACK_DELAY)