wdm_in_callback() will also touch this field, so we cannot change it without locking

Cc: stable@vger.kernel.org
Signed-off-by: NBjørn Mork <bjorn@mork.no>
Acked-by: NOliver Neukum <oneukum@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>