In case of a raid5/6 filesystem 'btrfs fi us' returns wrong values
without the root capabilities:
$ sudo btrfs fi us /tmp/raid5fs # as root
Overall:
Device size: 3.00GiB
Device allocated: 1.51GiB <--- OK
Device unallocated: 1.49GiB <--- OK
Device missing: 0.00B
Device slack: 0.00B
Used: 769.03MiB <--- OK
Free (estimated): 1.32GiB (min: 1.32GiB) <-OK
Free (statfs, df): 1.32GiB
Data ratio: 1.50 <--- OK
Metadata ratio: 1.50 <--- OK
Global reserve: 5.50MiB (used: 0.00B)
Multiple profiles: no
[...]
$ btrfs fi us /tmp/raid5fs # as user
WARNING: cannot read detailed chunk info, per-device usage will not be shown, run as root
Overall:
Device size: 3.00GiB
Device allocated: 0.00B <--- WRONG
Device unallocated: 3.00GiB <--- WRONG
Device missing: 0.00B
Device slack: 0.00B
Used: 0.00B <--- WRONG
Free (estimated): 0.00B (min: 8.00EiB) <- WRONG
Free (statfs, df): 1.32GiB
Data ratio: 0.00 <--- WRONG
Metadata ratio: 0.00 <--- WRONG
Global reserve: 5.50MiB (used: 0.00B)
Multiple profiles: no
[...]
The reason is that the BTRFS_IOC_SPACE_INFO ioctl doesn't return enough
information. To bypass it a scan of the chunks is required when a
raid5/6 profile is present.
To avoid providing wrong information, in case of a raid5/6 filesystem
without the root capabilities the "btrfs fi us" is not executed at all
and a warning with a suggestion to run it as root is printed.
$ ./btrfs fi us /tmp/t/
WARNING: cannot read detailed chunk info, per-device usage will not be shown, run as root
WARNING: due to the presence of a raid5/raid6 profile, we cannots compute some values;
WARNING: run as root instead.
Signed-off-by: Goffredo Baroncelli <kreijack@libero.it>
Signed-off-by: David Sterba <dsterba@suse.com>
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