results in an NULL pointer dereference when the backend device has not
yet been configured.
This patch adds an explicit check for DF_CONFIGURED, and fails with
-ENODEV to avoid this case.
Reported-by: Chris Boot <crb@tiger-computing.co.uk> Reported-by: Philip Gaw <pgaw@darktech.org.uk> Cc: Chris Boot <crb@tiger-computing.co.uk> Cc: Philip Gaw <pgaw@darktech.org.uk> Cc: stable@vger.kernel.org # 3.8+ Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>