dm mpath: log device name

Make the mapped device structure accessible to hardware handlers so error
messages can include the device name.

Signed-off-by: Edward Goggin <egoggin@emc.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/md/dm-hw-handler.h b/drivers/md/dm-hw-handler.h
index 32eff28..e0832e6 100644
--- a/drivers/md/dm-hw-handler.h
+++ b/drivers/md/dm-hw-handler.h
@@ -16,6 +16,7 @@
 struct hw_handler_type;
 struct hw_handler {
 	struct hw_handler_type *type;
+	struct mapped_device *md;
 	void *context;
 };