The map field in 'struct mapped_device' is an rcu pointer. Use rcu_dereference()
while accessing it.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>