pre job bitmap disable:
[
  {
    "type": "block-dirty-bitmap-disable",
    "data": {
      "node": "libvirt-3-format",
      "name": "b"
    }
  }
]
merge bitmpas:
[
  {
    "type": "block-dirty-bitmap-enable",
    "data": {
      "node": "libvirt-3-format",
      "name": "b"
    }
  },
  {
    "type": "block-dirty-bitmap-add",
    "data": {
      "node": "libvirt-3-format",
      "name": "c",
      "persistent": true,
      "disabled": true,
      "granularity": 65536
    }
  },
  {
    "type": "block-dirty-bitmap-merge",
    "data": {
      "node": "libvirt-3-format",
      "target": "c",
      "bitmaps": [
        {
          "node": "libvirt-2-format",
          "name": "c"
        }
      ]
    }
  }
]