[pve-devel] [PATCH pve-storage] fix #6561: zfspool: track refquota for subvolumes via user properties

[Shannon Sterz]

On Mon Jul 28, 2025 at 4:43 PM CEST, Shannon Sterz wrote:
> zfs itself does not track the refquota per snapshot so we need handle
> this ourselves. this implementation tries to do so by leveraging a
> user property per snapshot.
>
> Signed-off-by: Shannon Sterz <s.sterz at proxmox.com>
> ---
>
> this approach is not backward compatible, meaning that changes to volume
> sizes between snapshot before this patch will still be affected by this
> issue. however, it is fairly self-contained, does not require us to rely
> on the container config and works well with replication.
>
> we could fall back to resetting the refquota higher up in the call chain
> in case the storage doesn't manage to do it by itself. however, that
> comes with the potential downside of users messing with their configs
> und us resizing the disk when we shouldn't.
>
>  src/PVE/Storage/ZFSPoolPlugin.pm | 46 +++++++++++++++++++++++++++++++-
>  1 file changed, 45 insertions(+), 1 deletion(-)
>
> diff --git a/src/PVE/Storage/ZFSPoolPlugin.pm b/src/PVE/Storage/ZFSPoolPlugin.pm
> index cdf5868..2474b7f 100644
> --- a/src/PVE/Storage/ZFSPoolPlugin.pm
> +++ b/src/PVE/Storage/ZFSPoolPlugin.pm
> @@ -482,9 +482,28 @@ sub volume_size_info {
>  sub volume_snapshot {
>      my ($class, $scfg, $storeid, $volname, $snap) = @_;
>
> -    my $vname = ($class->parse_volname($volname))[1];
> +    my (undef, $vname, undef, undef, undef, undef, $format) = $class->parse_volname($volname);
>
>      $class->zfs_request($scfg, undef, 'snapshot', "$scfg->{pool}/$vname\@$snap");
> +
> +    # if this is a subvol, track refquota information with snapshot, as zfs does
> +    # not track this property via snapshosts and consequently does not roll it
> +    # back
> +    if ($format eq 'subvol') {
> +        my $refquota = $class->zfs_request(
> +            $scfg, undef, 'get', 'refquota', '-o', 'value', '-Hp', "$scfg->{pool}/$vname",
> +        );
> +
> +        chomp($refquota);
> +
> +        $class->zfs_request(
> +            $scfg,
> +            undef,
> +            'set',
> +            "pve-storage:refquota=${refquota}",
> +            "$scfg->{pool}/$vname\@$snap",
> +        );
> +    }
>  }
>
>  sub volume_snapshot_delete {
> @@ -503,6 +522,31 @@ sub volume_snapshot_rollback {
>
>      my $msg = $class->zfs_request($scfg, undef, 'rollback', "$scfg->{pool}/$vname\@$snap");
>
> +    if ($format eq 'subvol') {
> +    }
> +
> +    # if this is a subvol, check if we tracked the refquota manually via user properties and if so,
> +    # set it appropriatelly again
> +    if ($format eq 'subvol') {
> +        my $refquota = $class->zfs_request(
> +            $scfg,
> +            undef,
> +            'get',
> +            'pve-storage:refquota',
> +            '-o',
> +            'value',
> +            '-Hp',
> +            "$scfg->{pool}/$vname\@$snap",
> +        );
> +
> +        chomp($refquota);
> +
> +        if ($refquota =~ m/^\d+$/) {
> +            $class->zfs_request($scfg, undef, 'set', "refquota=${refquota}",
> +                "$scfg->{pool}/$vname");
> +        }
> +    }
> +
>      # we have to unmount rollbacked subvols, to invalidate wrong kernel
>      # caches, they get mounted in activate volume again
>      # see zfs bug #10931 https://github.com/openzfs/zfs/issues/10931
> --
> 2.47.2

Sorry just noticed i forgot to add the following trailers:

Reported-by: Lukas Wagner <l.wagner at proxmox.com>
Suggested-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>