quoted

  btrfs send introduced a part of code to read kernel-data
  from user-end using pipe. We need this part of code to be
  useable outside of send sub-cmd, so that developing
  service sub-cmd can use it.

What's 'service sub-cmd' please?

   at the moment 'btrfs service history <mnt>|<dev>'
   to show logs of maintenance.
   comments/suggestions welcome.

Thanks
-Anand