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: NEdward Goggin <egoggin@emc.com>
Signed-off-by: NAlasdair G Kergon <agk@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

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;
 };
 

drivers/md/dm-mpath.c

@@ -668,6 +668,9 @@ static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 		return -EINVAL;
 	}
 
+	m->hw_handler.md = dm_table_get_md(ti->table);
+	dm_put(m->hw_handler.md);
+
 	r = hwht->create(&m->hw_handler, hw_argc - 1, as->argv);
 	if (r) {
 		dm_put_hw_handler(hwht);

drivers/md/dm.c

@@ -1236,6 +1236,7 @@ void dm_put(struct mapped_device *md)
 		free_dev(md);
 	}
 }
+EXPORT_SYMBOL_GPL(dm_put);
 
 /*
  * Process the deferred bios