[pve-devel] [PATCH pve-storage v2] fix #6561: zfspool: track refquota for subvolumes via user properties

[Shannon Sterz]

Superseeded-by: https://lore.proxmox.com/pve-devel/20250729121151.159797-1-s.sterz@proxmox.com/T/#u

On Tue Jul 29, 2025 at 11:41 AM CEST, Shannon Sterz wrote:
> zfs itself does not track the refquota per snapshot so we need handle
> this ourselves. otherwise rolling back a volume that has been resize
> since the snapshot, will retain the new size. this is problematic, as
> it means the value in the guest config does not longer match the size
> of the disk on the storage.
>
> this implementation tries to do so by leveraging a user property per
> snapshot.
>
> Reported-by: Lukas Wagner <l.wagner at proxmox.com>
> Suggested-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
> Signed-off-by: Shannon Sterz <s.sterz at proxmox.com>
> ---
>  src/PVE/Storage/ZFSPoolPlugin.pm | 44 +++++++++++++++++++++++++++++++-
>  1 file changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/src/PVE/Storage/ZFSPoolPlugin.pm b/src/PVE/Storage/ZFSPoolPlugin.pm
> index cdf5868..d329abc 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\@$snap");
> +
> +    # if this is a subvol, track refquota information via user properties. zfs
> +    # does not track this property for snapshosts and consequently does not roll
> +    # it back. so track this information manually.
> +    if ($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 +522,29 @@ sub volume_snapshot_rollback {
>
>      my $msg = $class->zfs_request($scfg, undef, 'rollback', "$scfg->{pool}/$vname\@$snap");
>
> +    # if this is a subvol, check if we tracked the refquota manually via user
> +    # properties and if so, set it appropriatelly again.
> +    if ($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