First open locking changes were correctly applied to zvol_geom_open but
incorrectly applied to zvol_cdev_open, causing spa_namespace_lock to be
held indefinitely.
Make the first open locking in zvol_cdev_open match zvol_geom_open.
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes#13016
af1630c883