Fix lock order inversion with zvol_open() as it did not account
for use of zvols as vdevs. The latter use cases resulted in the
lock order inversion deadlocks that involved spa_namespace_lock
and bdev->bd_mutex.
Signed-off-by: Boris Protopopov <boris.protopopov@actifio.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #6065
Issue #6134