diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index db4d08c651311581a7f2c739767128f024b46aee..e3ec0eb5789b7b6b10c2c5c7d4743fe318c32a9f 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -358,7 +358,6 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 	dev_replace->cont_reading_from_srcdev_mode = read_src;
 	WARN_ON(!src_device);
 	dev_replace->srcdev = src_device;
-	WARN_ON(!tgt_device);
 	dev_replace->tgtdev = tgt_device;
 
 	btrfs_info_in_rcu(fs_info,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 70a87d4fe5fe5e2676c8ce5f43cfab71d2e70a4d..a8f8a2e39da694b21356296bf49c9e164f00272a 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2612,6 +2612,12 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	return ret;
 }
 
+/*
+ * Initialize a new device for device replace target from a given source dev
+ * and path.
+ *
+ * Return 0 and new device in @device_out, otherwise return < 0
+ */
 int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 				  const char *device_path,
 				  struct btrfs_device *srcdev,
@@ -2698,7 +2704,7 @@ int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
 	*device_out = device;
-	return ret;
+	return 0;
 
 error:
 	blkdev_put(bdev, FMODE_EXCL);