I don't publish the patched because aren't in a good shape. However I
really like the output. The example is a filesystem based on three
disks of 3GB.

It is clear that:
- - RAID0 uses all the disks
- - RAID1 uses two different disks

Comments are welcome.

Known bugs:
- - if a filesystem uses a disk but there is any chunk, the disk is not
shown (solvable)
- - this command need root capability (I use the BTRFS_IOC_TREE_SEARCH
to get the chunk info; so that is unavoidable)


ghigo@emulato:~$ sudo ./btrfs fi df /mnt/btrfs1/
[sudo] password for ghigo:
Path: /mnt/btrfs1
Summary:
  Disk_size:               9.00GB
  Disk_allocated:          1.83GB
  Disk_unallocated:        7.17GB
  Used:                  284.00KB
  Free_(Estimated):        6.76GB       (Max: 8.54GB, min: 4.96GB)
  Data_to_disk_ratio:        75 %

Allocated_area:
  Data,RAID0: Size:921.75MB, Used:256.00KB
     /dev/vdc     307.25MB
     /dev/vdb     307.25MB
     /dev/vdd     307.25MB

  Data,Single: Size:8.00MB, Used:0.00
     /dev/vdb       8.00MB

  System,RAID1: Size:8.00MB, Used:4.00KB
     /dev/vdd       8.00MB
     /dev/vdc       8.00MB

  System,Single: Size:4.00MB, Used:0.00
     /dev/vdb       4.00MB

  Metadata,RAID1: Size:460.94MB, Used:24.00KB
     /dev/vdb     460.94MB
     /dev/vdd     460.94MB

  Metadata,Single: Size:8.00MB, Used:0.00
     /dev/vdb       8.00MB

  Unused:
     /dev/vdb       2.23GB
     /dev/vdc       2.69GB
     /dev/vdd       2.24GB

Couple minor things, in order of personal opinion of severity:

* Devices should be listed in a consistent order; device names are
just too consistently similar

* System chunks shouldn't be listed between data and metadata; really,
they're just noise 99% of the time anyway

* I think it may be more useful to display each disk, with the
profiles in use underneath.  With a larger number of disks, that would
make it _much_ easier to tell at-a-glance what is currently on a disk
(that I may want to remove, or which I may suspect to be unreliable).

* I'd rename "Unused" to "Unallocated" for consistency with the section title

* (and I still detest the_underscores_between_all_the_words; it
doesn't make parsing significantly easier, and it's an eyesore)

* Three coats of blue paint plus a clear-coat is the One True Paint-Job.