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 02:29:38 AEST Boris Burkov wrote:
> Also wrong, but at least it's the "size" number?!
> 
> btrfs device usage (and btrfs filesystem usage) usually give
> pretty reasonable results without root on my systems, so this is sort of
> surprising to me, especially since it looks like we both have the same
> trivial raid/volume setup and you are on a relatively new kernel.
> e.g., on my system running 6.9:

I'm surprised that it worked for anyone, my experience was that it fails on 
all systems and I had assumed that was the general experience.

> Does the same discrepancy happen for you when running
> 'btrfs filesystem usage /' with and without root? That command gives me
> lots of useful, interesting output without root. e.g.,

For me btrfs fi usa gives me almost everything as non-root.  A bogus value for 
device slack is the only thing wrong.

# btrfs fi usa /
Overall:
    Device size:		476.37GiB
    Device allocated:		222.07GiB
    Device unallocated:		254.29GiB
    Device missing:		    0.00B
    Device slack:		  1.50KiB
    Used:			209.94GiB
    Free (estimated):		263.99GiB	(min: 136.84GiB)
    Free (statfs, df):		263.99GiB
    Data ratio:			     1.00
    Metadata ratio:		     2.00
    Global reserve:		385.50MiB	(used: 0.00B)
    Multiple profiles:		       no

Data,single: Size:216.01GiB, Used:206.31GiB (95.51%)
   /dev/mapper/root	216.01GiB

Metadata,DUP: Size:3.00GiB, Used:1.81GiB (60.50%)
   /dev/mapper/root	  6.00GiB

System,DUP: Size:32.00MiB, Used:48.00KiB (0.15%)
   /dev/mapper/root	 64.00MiB

Unallocated:
   /dev/mapper/root	254.29GiB

$ btrfs fi usa /
WARNING: cannot read detailed chunk info, per-device usage will not be shown, 
run as root
Overall:
    Device size:		476.37GiB
    Device allocated:		222.07GiB
    Device unallocated:		254.29GiB
    Device missing:		    0.00B
    Device slack:		 16.00EiB
    Used:			209.94GiB
    Free (estimated):		263.99GiB	(min: 136.84GiB)
    Free (statfs, df):		263.99GiB
    Data ratio:			     1.00
    Metadata ratio:		     2.00
    Global reserve:		385.50MiB	(used: 0.00B)
    Multiple profiles:		       no

Data,single: Size:216.01GiB, Used:206.31GiB (95.51%)

Metadata,DUP: Size:3.00GiB, Used:1.81GiB (60.50%)

System,DUP: Size:32.00MiB, Used:48.00KiB (0.15%)

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