@yangdongsheng As for simplify combination, I think I did a confusing trick here. :)
The more readable cfg should be:
```
                - fs_pool:
                    vol_download_upload_pool_type = "fs"
                    vol_download_upload_pool_name = "fs-pool"
                    vol_download_upload_pool_target = "fs-pool"
                    vol_download_upload_vol_name = "fs-vol"
                    variants:
                        - fs1:
                            no acl_test
                        - fs2:
                            only acl_test
                            action_lookup = "connect_driver:QEMU vol_name:fs-vol"
```

if I write it this way, two new filters: 'fs1' and 'fs2' will be introduced.