int ret;
        u64 offset;
        u64 max_extent_size;
-
-       bool (*use_bitmap_op)(struct btrfs_free_space_ctl *,
-                             struct btrfs_free_space *);
+       struct btrfs_free_space_op test_free_space_ops = {
+               .recalc_thresholds = cache->free_space_ctl->op->recalc_thresholds,
+               .use_bitmap = test_use_bitmap,
+       };
+       struct btrfs_free_space_op *orig_free_space_ops;
 
        test_msg("Running space stealing from bitmap to extent\n");
 
         * that forces use of bitmaps as soon as we have at least 1
         * extent entry.
         */
-       use_bitmap_op = cache->free_space_ctl->op->use_bitmap;
-       cache->free_space_ctl->op->use_bitmap = test_use_bitmap;
+       orig_free_space_ops = cache->free_space_ctl->op;
+       cache->free_space_ctl->op = &test_free_space_ops;
 
        /*
         * Extent entry covering free space range [128Mb - 256Kb, 128Mb - 128Kb[
        if (ret)
                return ret;
 
-       cache->free_space_ctl->op->use_bitmap = use_bitmap_op;
+       cache->free_space_ctl->op = orig_free_space_ops;
        __btrfs_remove_free_space_cache(cache->free_space_ctl);
 
        return 0;