rxrpc: Fix missing notification

Under some circumstances, rxrpc will fail a transmit a packet through the
underlying UDP socket (ie. UDP sendmsg returns an error).  This may result
in a call getting stuck.

In the instance being seen, where AFS tries to send a probe to the Volume
Location server, tracepoints show the UDP Tx failure (in this case returing
error 99 EADDRNOTAVAIL) and then nothing more:

 afs_make_vl_call: c=0000015d VL.GetCapabilities
 rxrpc_call: c=0000015d NWc u=1 sp=rxrpc_kernel_begin_call+0x106/0x170 [rxrpc] a=00000000dd89ee8a
 rxrpc_call: c=0000015d Gus u=2 sp=rxrpc_new_client_call+0x14f/0x580 [rxrpc] a=00000000e20e4b08
 rxrpc_call: c=0000015d SEE u=2 sp=rxrpc_activate_one_channel+0x7b/0x1c0 [rxrpc] a=00000000e20e4b08
 rxrpc_call: c=0000015d CON u=2 sp=rxrpc_kernel_begin_call+0x106/0x170 [rxrpc] a=00000000e20e4b08
 rxrpc_tx_fail: c=0000015d r=1 ret=-99 CallDataNofrag

The problem is that if the initial packet fails and the retransmission
timer hasn't been started, the call is set to completed and an error is
returned from rxrpc_send_data_packet() to rxrpc_queue_packet().  Though
rxrpc_instant_resend() is called, this does nothing because the call is
marked completed.

So rxrpc_notify_socket() isn't called and the error is passed back up to
rxrpc_send_data(), rxrpc_kernel_send_data() and thence to afs_make_call()
and afs_vl_get_capabilities() where it is simply ignored because it is
assumed that the result of a probe will be collected asynchronously.

Fileserver probing is similarly affected via afs_fs_get_capabilities().

Fix this by always issuing a notification in __rxrpc_set_call_completion()
if it shifts a call to the completed state, even if an error is also
returned to the caller through the function return value.

Also put in a little bit of optimisation to avoid taking the call
state_lock and disabling softirqs if the call is already in the completed
state and remove some now redundant rxrpc_notify_socket() calls.

Fixes: f5c17aa ("rxrpc: Calls should only have one terminal state")
Reported-by: Gerry Seidman <gerry@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>

net/rxrpc/call_event.c

@@ -320,7 +320,6 @@ void rxrpc_process_call(struct work_struct *work)
 
 	if (call->state == RXRPC_CALL_COMPLETE) {
 		del_timer_sync(&call->timer);
-		rxrpc_notify_socket(call);
 		goto out_put;
 	}
 

net/rxrpc/conn_event.c

@@ -173,10 +173,9 @@ static void rxrpc_abort_calls(struct rxrpc_connection *conn,
 			else
 				trace_rxrpc_rx_abort(call, serial,
 						     conn->abort_code);
-			if (rxrpc_set_call_completion(call, compl,
-						      conn->abort_code,
-						      conn->error))
-				rxrpc_notify_socket(call);
+			rxrpc_set_call_completion(call, compl,
+						  conn->abort_code,
+						  conn->error);
 		}
 	}
 

net/rxrpc/input.c

@@ -275,7 +275,6 @@ static bool rxrpc_end_tx_phase(struct rxrpc_call *call, bool reply_begun,
 
 	case RXRPC_CALL_SERVER_AWAIT_ACK:
 		__rxrpc_call_completed(call);
-		rxrpc_notify_socket(call);
 		state = call->state;
 		break;
 
@@ -1013,9 +1012,8 @@ static void rxrpc_input_abort(struct rxrpc_call *call, struct sk_buff *skb)
 
 	_proto("Rx ABORT %%%u { %x }", sp->hdr.serial, abort_code);
 
-	if (rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
-				      abort_code, -ECONNABORTED))
-		rxrpc_notify_socket(call);
+	rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
+				  abort_code, -ECONNABORTED);
 }
 
 /*
@@ -1102,7 +1100,6 @@ static void rxrpc_input_implicit_end_call(struct rxrpc_sock *rx,
 	spin_lock(&rx->incoming_lock);
 	__rxrpc_disconnect_call(conn, call);
 	spin_unlock(&rx->incoming_lock);
-	rxrpc_notify_socket(call);
 }
 
 /*

net/rxrpc/peer_event.c

@@ -289,9 +289,7 @@ static void rxrpc_distribute_error(struct rxrpc_peer *peer, int error,
 
 	hlist_for_each_entry_rcu(call, &peer->error_targets, error_link) {
 		rxrpc_see_call(call);
-		if (call->state < RXRPC_CALL_COMPLETE &&
-		    rxrpc_set_call_completion(call, compl, 0, -error))
-			rxrpc_notify_socket(call);
+		rxrpc_set_call_completion(call, compl, 0, -error);
 	}
 }
 

net/rxrpc/recvmsg.c

@@ -73,6 +73,7 @@ bool __rxrpc_set_call_completion(struct rxrpc_call *call,
 		call->state = RXRPC_CALL_COMPLETE;
 		trace_rxrpc_call_complete(call);
 		wake_up(&call->waitq);
+		rxrpc_notify_socket(call);
 		return true;
 	}
 	return false;
@@ -83,11 +84,13 @@ bool rxrpc_set_call_completion(struct rxrpc_call *call,
 			       u32 abort_code,
 			       int error)
 {
-	bool ret;
+	bool ret = false;
 
-	write_lock_bh(&call->state_lock);
-	ret = __rxrpc_set_call_completion(call, compl, abort_code, error);
-	write_unlock_bh(&call->state_lock);
+	if (call->state < RXRPC_CALL_COMPLETE) {
+		write_lock_bh(&call->state_lock);
+		ret = __rxrpc_set_call_completion(call, compl, abort_code, error);
+		write_unlock_bh(&call->state_lock);
+	}
 	return ret;
 }
 
@@ -101,11 +104,13 @@ bool __rxrpc_call_completed(struct rxrpc_call *call)
 
 bool rxrpc_call_completed(struct rxrpc_call *call)
 {
-	bool ret;
+	bool ret = false;
 
-	write_lock_bh(&call->state_lock);
-	ret = __rxrpc_call_completed(call);
-	write_unlock_bh(&call->state_lock);
+	if (call->state < RXRPC_CALL_COMPLETE) {
+		write_lock_bh(&call->state_lock);
+		ret = __rxrpc_call_completed(call);
+		write_unlock_bh(&call->state_lock);
+	}
 	return ret;
 }
 

net/rxrpc/sendmsg.c

@@ -261,10 +261,8 @@ static int rxrpc_queue_packet(struct rxrpc_sock *rx, struct rxrpc_call *call,
 		case -ENETUNREACH:
 		case -EHOSTUNREACH:
 		case -ECONNREFUSED:
-			if (rxrpc_set_call_completion(call,
-						      RXRPC_CALL_LOCAL_ERROR,
-						      0, ret))
-				rxrpc_notify_socket(call);
+			rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
+						  0, ret);
 			goto out;
 		}
 		_debug("need instant resend %d", ret);