btrfs: skip space_cache v1 setup when not using it

If we are not using space cache v1, we should not create the free space
object or free space inodes. This comes up when we delete the existing
free space objects/inodes when migrating to v2, only to see them get
recreated for every dirtied block group.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/block-group.c

@@ -2340,6 +2340,9 @@ static int cache_save_setup(struct btrfs_block_group *block_group,
 	int retries = 0;
 	int ret = 0;
 
+	if (!btrfs_test_opt(fs_info, SPACE_CACHE))
+		return 0;
+
 	/*
 	 * If this block group is smaller than 100 megs don't bother caching the
 	 * block group.