Re: btrfs thinks fs is full, though 11GB should be still free

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

On 2023/12/12 08:53, Christoph Anton Mitterer wrote:
> Hey Qu
>
> On Tue, 2023-12-12 at 07:27 +1030, Qu Wenruo wrote:
>> Is your current mounted subvolume the fs tree? Or already the data
>> subvolume?
>
> Well actually both, I always have a "service" mountpoint of the root
> volume as well, and just unmounted that to no confuse with "double"
> mount entries.
>
> In reality it looks like:
> # mount | grep vdb
> /dev/vdb on /data/main type btrfs (rw,noatime,space_cache=v2,subvolid=257,subvol=/data)
> /dev/vdb on /data/btrfs-top-level-subvolumes/data-main type btrfs (rw,noatime,space_cache=v2,subvolid=5,subvol=/)
>
> But all data (except for 2 empty dirs, where on other systems I would
> place btrbk snapshots) is in the data subvolume:
>
> data/btrfs-top-level-subvolumes/data-main# ls -al
> total 16
> drwxr-xr-x 1 root root 26 Feb 21  2023 .
> drwxr-xr-x 1 root root 30 Nov  9 23:49 ..
> drwxr-xr-x 1 root root 20 Feb 21  2023 data
> drwx------ 1 root root 10 Feb 21  2023 snapshots
> /data/btrfs-top-level-subvolumes/data-main# du --apparent-size --total -s --si *
> 29G	data
> 10	snapshots
> 29G	total
>
>
>> If the latter case, there are some files you can not access from your
>> current mount point.
>
> No it's not that (that would have been quite embarrassing ^^).
> /data/btrfs-top-level-subvolumes/data-main# tree -a snapshots/
> snapshots/
> └── btrbk
>
> 2 directories, 0 files
>
>
>> Thus it's recommended to use qgroup to show a correct full view of
>> the
>> used space by each subvolume.
>
> Uhm... qgroups? How would they help me here?

Shows exactly which subvolumes uses how many bytes, including orphan
ones which is pending for deletion.

Thanks,
Qu
>
> Cheers,
> Chris.
>