disk_space: Support btrfs backend #2159
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Btrfs is too smart for the statvfs based backend (i.e., only counting blocks leads to wrong numbers). For example, a btrfs disk with a lot of de-duplicated blocks (via the copy on write mechanism) might have a drastically over-reported disk usage. The btrfs backend is currently implemented by parsing the output of the `btrfs filesystem usage --raw` command. This is suboptimal, as this now relies on the command output not changing. Vendoring the algorithm used internally by the `btrfs` command does not seem to be a reasonable alternative, considering that the code[1] is rather complex, low level and would require semi-constant maintenance. Additionally, the c code would need bindings to be usable from rust. I assume, that the `btrfs` command output will stay rather similar in the future, as a lot of tools rely on directly parsing it (see the various scripts in the issue, this commit fixes). [1]: https://github.com/kdave/btrfs-progs/blob/eeab081e9d9fbdf4583122ed1caedf541383cf2d/cmds/filesystem-usage.c#L442 Fixes: greshake#1654
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Btrfs is too smart for the statvfs based backend (i.e., only counting blocks leads to wrong numbers).
For example, a btrfs disk with a lot of de-duplicated blocks (via the copy on write mechanism) might have a drastically over-reported disk usage.
The btrfs backend is currently implemented by parsing the output of the
btrfs filesystem usage --rawcommand. This is suboptimal, as this now relies on the command output not changing.Vendoring the algorithm used internally by the
btrfscommand does not seem to be a reasonable alternative, considering that the code1 is rather complex, low level and would require semi-constant maintenance. Additionally, the c code would need bindings to be usable from rust.I assume, that the
btrfscommand output will stay rather similar in the future, as a lot of tools rely on directly parsing it (see the various scripts in the issue, this commit fixes).Fixes: #1654