Re: [RFC pve-container 1/1] mountpoint backup: allow changing backup flag at runtime

["Thomas Ellmenreich" <t.ellmenreich@proxmox.com>]

On Mon Aug 31, 2026 at 12:36 PM CEST, Filip Schauer wrote:

[snip]

>> +# Checks whether the changed properties can be applied at runtime. It only
>> +# returns true if all changes can be applied in this way. If even one
>> +# property cannot be applied, returns false to ensure changes are applied
>> +# as a unit.
>> +my $mountpoint_config_fast_plug_safe = sub {
>> +    my ($new, $old) = @_;
>> +    my @fast_plug_safe_keys = ("backup");
>> +
>> +    for my $key (uniq(keys %$new, keys %$old)) {
>> +        next if first { $_ eq $key } @fast_plug_safe_keys;
>> +        return 0 if ($new->{$key} // '') ne ($old->{$key} // '');
>
>  From testing I noticed that when toggling `backup` on a mount point
> specifying a custom `idmap`, the `backup` property is still marked as
> pending.
> The reason seems to be that this is comparing array references. Even if
> the arrays both hold the same data, the references still differ.

Ack, thanks for this, stupid mistake.

>
>> +    }
>> +
>> +    1;
>> +};
>> +
>>   sub apply_pending_mountpoint {
>>       my ($class, $vmid, $conf, $opt, $storecfg, $running) = @_;
>>   
>>       my $mp = $class->parse_volume($opt, $conf->{pending}->{$opt});
>>       my $old = $conf->{$opt};
>> +
>> +    if (exists($conf->{$opt}) && $running) {
>> +        if ($mountpoint_config_fast_plug_safe->($mp, $class->parse_volume($opt, $old))) {
>> +            return;
>> +        }
>> +        die "skip\n"; # don't try to hotplug over existing mp
>
> Doesn't this make the later `die "skip\n" if $running && defined($old);`
> unreachable?

Good catch, yes. I think it will be unreachable, although I'm not sure what to
do with the open #TODO, especially since I don't quite understand what the
exact meaning of "changing" is in this context.

```perl
if ($mp->{type} eq 'volume' && $mp->{volume} =~ $PVE::LXC::NEW_DISK_RE) {
    # more code
} else {
    die "skip\n" if $running && defined($old); # TODO: "changing" mount points?
    # more code
}
```

[snip]