Re: btrfs-progs: btrfs dev usa as non-root is wrong and should just abort

[Russell Coker <russell@coker.com.au>]

On Thursday, 11 July 2024 07:13:25 AEST Qu Wenruo wrote:
> 在 2024/7/10 21:22, Russell Coker 写道:
> > Below is the difference between running btrfs dev usa as root and non-root
> > on a laptop with kernel 6.8.12-amd64.  When run as non-root it gets
> > everything wrong and in my tests I have never been able to see it give
> > nay accurate data as non-root.  I think it should just abort with an
> > error in that situation, there's no point in giving a wrong answer.
> > 
> > # btrfs dev usa /
> > /dev/mapper/root, ID: 1
> > 
> >     Device size:           476.37GiB
> >     Device slack:            1.50KiB
> >     Data,single:           216.01GiB
> >     Metadata,DUP:            6.00GiB
> >     System,DUP:             64.00MiB
> >     Unallocated:           254.29GiB
> > 
> > $ btrfs dev usa /
> > WARNING: cannot read detailed chunk info, per-device usage will not be
> > shown, run as root
> > /dev/mapper/root, ID: 1
> > 
> >     Device size:           952.73MiB
> >     Device slack:           16.00EiB
> >     Unallocated:           476.37GiB
> 
> Mind to post the raw result?
> 
> The 16EiB output definitely means something wrong.
> 
> So far the result looks like btrfs-progs is interpret the result wrong
> with some offset of the result.
> 
> In my case, non-root call of "btrfs dev usage" always shows the slack as
> 0, and unallocated as N/A, so the 16EiB looks like some shift.

# btrfs dev usa -b /
/dev/mapper/root, ID: 1
   Device size:          511493395968
   Device slack:               1536
   Data,single:          231936622592
   Metadata,DUP:         6442450944
   System,DUP:             67108864
   Unallocated:          273047212032

$ btrfs dev usa -b /
WARNING: cannot read detailed chunk info, per-device usage will not be shown, 
run as root
/dev/mapper/root, ID: 1
   Device size:           999010539
   Device slack:         18446743563215167723
   Unallocated:          511493394432

> And what's the version of the btrfs-progs?

The Debian package version is 6.6.3-1.2+b1.

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