dm mpath: don't call dm_get_device in multipath_message

When mutipath_message is called with an action and a device, it needs to
find the pgpath that matches that device. dm_get_device() is not the
right function for this. dm_get_device() will look for a table_device
matching the requested path in use by either the live or inactive table.
If it doesn't find the device, dm_get_device() will open it and add it
to the table. Means that multipath_message will accept any block device,
add it to the table if not present, and then look through the pgpaths
to see if it finds a match. Afterwards it will remove the device if it
was not previously in the table devices list.

This is the only function that can modify the device list of a table
besides the constructors and destructors, and it can only do this when
it was passed an invalid message.  Instead, multipath_message() should
call dm_devt_from_path() to get the device dev_t, and match that against
its pgpaths.
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

drivers/md/dm-mpath.c

@@ -1419,8 +1419,7 @@ static int reinstate_path(struct pgpath *pgpath)
 /*
  * Fail or reinstate all paths that match the provided struct dm_dev.
  */
-static int action_dev(struct multipath *m, struct dm_dev *dev,
-		      action_fn action)
+static int action_dev(struct multipath *m, dev_t dev, action_fn action)
 {
 	int r = -EINVAL;
 	struct pgpath *pgpath;
@@ -1428,7 +1427,7 @@ static int action_dev(struct multipath *m, struct dm_dev *dev,
 
 	list_for_each_entry(pg, &m->priority_groups, list) {
 		list_for_each_entry(pgpath, &pg->pgpaths, list) {
-			if (pgpath->path.dev == dev)
+			if (pgpath->path.dev->bdev->bd_dev == dev)
 				r = action(pgpath);
 		}
 	}
@@ -1959,7 +1958,7 @@ static int multipath_message(struct dm_target *ti, unsigned int argc, char **arg
 			     char *result, unsigned int maxlen)
 {
 	int r = -EINVAL;
-	struct dm_dev *dev;
+	dev_t dev;
 	struct multipath *m = ti->private;
 	action_fn action;
 	unsigned long flags;
@@ -2008,7 +2007,7 @@ static int multipath_message(struct dm_target *ti, unsigned int argc, char **arg
 		goto out;
 	}
 
-	r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
+	r = dm_devt_from_path(argv[1], &dev);
 	if (r) {
 		DMWARN("message: error getting device %s",
 		       argv[1]);
@@ -2017,8 +2016,6 @@ static int multipath_message(struct dm_target *ti, unsigned int argc, char **arg
 
 	r = action_dev(m, dev, action);
 
-	dm_put_device(ti, dev);
-
 out:
 	mutex_unlock(&m->work_mutex);
 	return r;