/usr/bin/btrfs-map-logical: unrecognized option '--help'
usage: btrfs-map-logical [options] device

Map logical address on a device

-l OFFSET                 logical extent to map
-c COPY                   copy of the extent to read (usually 1 or 2)
-o FILE                   output file to hold the extent
-b BYTES                  number of bytes to read