diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 1f6f25a..9b41e4d 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -42,6 +42,9 @@
 
 	struct block_device *bdev;
 
+	/* the mode sent to open_bdev_exclusive */
+	fmode_t mode;
+
 	char *name;
 
 	/* the internal btrfs device id */