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

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2024/7/11 13:12, Russell Coker 写道:
> 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

The device size is 4K aligned.

I guess it's some older fs? As newer mkfs would always round down to the
sector size.


>     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.
>

It may be easier to debug by trying a newer version of btrfs-progs.

And since I'm not sure if it's the unalignment causing problems, you may
want to resize the fs by:

# btrfs device resize -1M <mnt>

Then resize to max (which should always align the fs correctly):

# btrfs device resize max <mnt>

And then check if the size is aligned to 4K and if the problem has changed.

Thanks,
Qu