Map btrfs logical extent to physical extent
btrfs-map-logical <options> <device>
btrfs-map-logical can be used to find out what the physical offsets are on the mirrors, the result is dumped into stdout in default.
Mainly used for debug purpose.
Logical extent to map.
Copy of the extent to read(usually 1 or 2).
Output file to hold the extent.
Number of bytes to read.
btrfs-map-logical will return 0 if no error happened. If any problems happened, 1 will be returned.