Android A/B updates allows roll back of updates that fail to boot, rolling back system, vendor partitions. BUT if update modifies the userdata partition before failing, cannot roll back modifications, and Android does not support updated userdata with old system/vendor partitions. If the file system supports snapshots, use them! We are adding snapshot support to F2FS. If no filesystem support, consider a block level solution. We will discuss a dm-snap based solution vs a new solution from Google called dm-bow.