utility to manage mappings of dm-writeboost devices

 Writeboost is a utility to activate dm-writeboost device mappings.
 .
 dm-writeboost is an OS-level IO controller that builds logs from in-coming
 writes (data and metadata) and then writes the logs sequentially similar
 to log-structured filesystem. As a further extension, dm-writeboost
 supports read-caching which also writes data sequentially.