Drivers: hv: util: Fcopy: Fix a rescind processing issue

Fcopy may use a char device to support the communication between
the user level daemon and the driver. When the Fcopy channel is rescinded
we need to make sure that the char device is fully cleaned up before
we can process a new Fcopy offer from the host. Implement this logic.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/hv_fcopy.c

@@ -61,6 +61,7 @@ static DECLARE_WORK(fcopy_send_work, fcopy_send_data);
 static const char fcopy_devname[] = "vmbus/hv_fcopy";
 static u8 *recv_buffer;
 static struct hvutil_transport *hvt;
+static struct completion release_event;
 /*
  * This state maintains the version number registered by the daemon.
  */
@@ -317,6 +318,7 @@ static void fcopy_on_reset(void)
 
 	if (cancel_delayed_work_sync(&fcopy_timeout_work))
 		fcopy_respond_to_host(HV_E_FAIL);
+	complete(&release_event);
 }
 
 int hv_fcopy_init(struct hv_util_service *srv)
@@ -324,6 +326,7 @@ int hv_fcopy_init(struct hv_util_service *srv)
 	recv_buffer = srv->recv_buffer;
 	fcopy_transaction.recv_channel = srv->channel;
 
+	init_completion(&release_event);
 	/*
 	 * When this driver loads, the user level daemon that
 	 * processes the host requests may not yet be running.
@@ -345,4 +348,5 @@ void hv_fcopy_deinit(void)
 	fcopy_transaction.state = HVUTIL_DEVICE_DYING;
 	cancel_delayed_work_sync(&fcopy_timeout_work);
 	hvutil_transport_destroy(hvt);
+	wait_for_completion(&release_event);
 }