dm zoned: ignore metadata zone in dmz_alloc_zone()

When looking up zones in dmz_alloc_zone() we need to ignore
metadata zones so as not to accidentally overwrite metadata.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-zoned-metadata.c

@@ -1907,7 +1907,13 @@ struct dm_zone *dmz_alloc_zone(struct dmz_metadata *zmd, unsigned long flags)
 		zone = NULL;
 		goto again;
 	}
+	if (dmz_is_meta(zone)) {
+		struct dmz_dev *dev = dmz_zone_to_dev(zmd, zone);
 
+		dmz_dev_warn(dev, "Zone %u has metadata", zone->id);
+		zone = NULL;
+		goto again;
+	}
 	return zone;
 }