Re: [pve-devel] [PATCH qemu-server 2/6] drive: factor out read-only helper

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

On June 7, 2021 11:29 am, Stefan Reiter wrote:
> On 6/4/21 11:47 AM, Fabian Grünbichler wrote:
>> we also need it for efidisks.
>> 
>> Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
>> ---
>>   PVE/QemuServer.pm       |  8 ++------
>>   PVE/QemuServer/Drive.pm | 10 ++++++++++
>>   2 files changed, 12 insertions(+), 6 deletions(-)
>> 
>> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
>> index 25ac052..0d49415 100644
>> --- a/PVE/QemuServer.pm
>> +++ b/PVE/QemuServer.pm
>> @@ -48,7 +48,7 @@ use PVE::QemuServer::Helpers qw(min_version config_aware_timeout);
>>   use PVE::QemuServer::Cloudinit;
>>   use PVE::QemuServer::CGroup;
>>   use PVE::QemuServer::CPUConfig qw(print_cpu_device get_cpu_options);
>> -use PVE::QemuServer::Drive qw(is_valid_drivename drive_is_cloudinit drive_is_cdrom parse_drive print_drive);
>> +use PVE::QemuServer::Drive qw(is_valid_drivename drive_is_cloudinit drive_is_cdrom drive_is_read_only parse_drive print_drive);
>>   use PVE::QemuServer::Machine;
>>   use PVE::QemuServer::Memory;
>>   use PVE::QemuServer::Monitor qw(mon_cmd);
>> @@ -3662,11 +3662,7 @@ sub config_to_command {
>>   	my $drive_cmd = print_drive_commandline_full($storecfg, $vmid, $drive, $pbs_name);
>>   
>>   	# extra protection for templates, but SATA and IDE don't support it..
>> -	my $read_only = PVE::QemuConfig->is_template($conf)
>> -	    && $drive->{interface} ne 'sata'
>> -	    && $drive->{interface} ne 'ide';
>> -
>> -	$drive_cmd .= ',readonly=on' if $read_only;
>> +	$drive_cmd .= ',readonly=on' if drive_is_read_only($conf, $drive);
>>   
>>   	push @$devices, '-drive',$drive_cmd;
>>   	push @$devices, '-device', print_drivedevice_full(
>> diff --git a/PVE/QemuServer/Drive.pm b/PVE/QemuServer/Drive.pm
>> index 146a4ab..0408e32 100644
>> --- a/PVE/QemuServer/Drive.pm
>> +++ b/PVE/QemuServer/Drive.pm
>> @@ -12,6 +12,7 @@ our @EXPORT_OK = qw(
>>   is_valid_drivename
>>   drive_is_cloudinit
>>   drive_is_cdrom
>> +drive_is_read_only
>>   parse_drive
>>   print_drive
>>   );
>> @@ -422,6 +423,15 @@ sub drive_is_cdrom {
>>       return $drive && $drive->{media} && ($drive->{media} eq 'cdrom');
>>   }
>>   
>> +sub drive_is_read_only {
> 
> I really don't like this name, this checks if the drive *should* be 
> read-only, and only related to template backups, not in general.

yeah, `drive_should_be_read_only` would be more apt, but also sounds 
wrong. I did have the non-template case in mind as well (e.g., adding a 
'ro' flag to the drive in our VM config as a future addon, like we have 
for container mountpoints).

> 
> Maybe 'drive_template_read_only'?
> 
> The function does two pretty unrelated things in general IMO, so maybe 
> it would be clearer to do the is_template check at call site and make 
> this 'drive_supports_read_only', even if it causes a little bit more 
> duplication.

would work as well. or we drop all of it and no longer mark any drives 
as read-only, if we use the patch that adds '-snapshot' for 
'start-template-for-backup'? at the risk of re-doing it if we ever add a 
'ro' property for individual regular disks/drives..

> 
>> +    my ($conf, $drive) = @_;
>> +
>> +    return 0 if !PVE::QemuConfig->is_template($conf);
>> +
>> +    # don't support being marked read-only
>> +    return $drive->{interface} ne 'sata' && $drive->{interface} ne 'ide';
>> +}
>> +
>>   # ideX = [volume=]volume-id[,media=d][,cyls=c,heads=h,secs=s[,trans=t]]
>>   #        [,snapshot=on|off][,cache=on|off][,format=f][,backup=yes|no]
>>   #        [,rerror=ignore|report|stop][,werror=enospc|ignore|report|stop]
>> 
>