bug#80516: df --total returns wrong values

Hi Thomas,

Rorschach <[email protected]> writes:

> The `df --total` command returns incorrect values for total disk space
> (total, used, available, etc.). It simply adds all values without
> considering whether they are already in use. See the CSV file (output of
> `df --total`) and the LibreOffice Calc spreadsheet, where the values are
> calculated correctly by excluding duplicates.

I am copying the 'df' output you shared, so that others on the mailing
list can see it more easily:

    Dateisystem	Typ	Größe	Benutzt	Verf.	Verw%	Eingehängt auf
    dev	devtmpfs	32G	0	32G	0%	/dev
    run	tmpfs	32G	2,4M	32G	1%	/run
    efivarfs	efivarfs	128K	47K	77K	38%	/sys/firmware/efi/efivars
    /dev/sda2	btrfs	222G	126G	94G	58%	/
    tmpfs	tmpfs	32G	0	32G	0%	/dev/shm
    none	tmpfs	1,0M	0	1,0M	0%	/run/credentials/systemd-journald.service
    none	tmpfs	1,0M	0	1,0M	0%	/run/credentials/systemd-resolved.service
    /dev/sda2	btrfs	222G	126G	94G	58%	/srv
    /dev/sda2	btrfs	222G	126G	94G	58%	/var/tmp
    /dev/sda2	btrfs	222G	126G	94G	58%	/root
    /dev/sda2	btrfs	222G	126G	94G	58%	/var/log
    /dev/sda2	btrfs	222G	126G	94G	58%	/home
    /dev/sda2	btrfs	222G	126G	94G	58%	/var/cache
    tmpfs	tmpfs	32G	76K	32G	1%	/tmp
    /dev/sda1	vfat	2,0G	440M	1,6G	22%	/boot
    /dev/sdb1	ntfs3	932G	583G	349G	63%	/home/tom/Daten
    tmpfs	tmpfs	6,3G	72K	6,3G	1%	/run/user/1000
    total	-	2,6T	1,5T	1,2T	57%	-

It looks like the duplicate entries you mention are btrfs subvolumes. If
so, that is the expected behavior, albeit a bit awkward.

I will link a good explanation that Pádraig Brady wrote, instead of
poorly paraphrasing it [1].

Collin

[1] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=17676#8