[pve-devel] [PATCH qemu-server] Revert "resize_vm: request new size from storage after resizing"

[Fabian Ebner]

On 3/6/20 7:55 PM, Thomas Lamprecht wrote:
> On 3/4/20 10:51 AM, Fabian Ebner wrote:
>> This reverts commit b5490d8a98e5e7328eb4cebb0ae0b60e6d406c38.
>>
>> When resizing a volume of a running VM, a qmp block_resize command
>> is issued. This is non-blocking, so the size on the storage immediately
>> after issuing the command might still be the old one.
>>
>> This is part of the issue reported in bug #2621.
>>
>> Signed-off-by: Fabian Ebner <f.ebner at proxmox.com>
>> ---
>>   PVE/API2/Qemu.pm | 3 +--
>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/PVE/API2/Qemu.pm b/PVE/API2/Qemu.pm
>> index caca430..d0dd2dc 100644
>> --- a/PVE/API2/Qemu.pm
>> +++ b/PVE/API2/Qemu.pm
>> @@ -3586,8 +3586,7 @@ __PACKAGE__->register_method({
>>   
>>   	    PVE::QemuServer::qemu_block_resize($vmid, "drive-$disk", $storecfg, $volid, $newsize);
>>   
>> -	    my $effective_size = eval { PVE::Storage::volume_size_info($storecfg, $volid, 3); };
>> -	    $drive->{size} = $effective_size // $newsize;
>> +	    $drive->{size} = $newsize;
>>   	    $conf->{$disk} = PVE::QemuServer::print_drive($drive);
>>   
>>   	    PVE::QemuConfig->write_config($vmid, $conf);
>>
> 
> don't we want to await that operation to be finished?

AFAIU the QMP command has been fully issued, i.e. we already got a 
response from the QMP socket. So the operation is blocking from a 
QMP-interaction perspective, but not from the backing storage's perspective.
I can see that my commit message is not clear about that. With a local 
filesystem I couldn't trigger the issue, but with a GluserFS storage it 
happens consistently on my setup.

> Or let the storage backend tell us
> anyway what aligned/rounded-up size it requested from qemu-img, zfs, ...?
> 

But for GlusterFS that can be the old size.
Do you mean let volume_resize return the new size it used? It already 
returns something else (see the following) and changing that would be a 
breaking change.

Message for commit c1175c9264b57302d64fb697af589578d537d1e6 in qemu-server:

     add qemu_block_resize

     this call storage plugin resize first.
     storage plugin will
       return undef if we don't need to call qmp block_resize
     or
      return 1 if we need to call qmp block_resize