Re: [pve-devel] [PATCH qemu-server 1/3] fix #2816: restore: remove timeout when allocating disks

[Dominik Csapak <d.csapak@proxmox.com>]

comment inline:

On 9/12/23 11:16, Fiona Ebner wrote:
> 10 minutes is not long enough when disks are large and/or network
> storages are used when preallocation is not disabled. The default is
> metadata preallocation for qcow2, so there are still reports of the
> issue [0][1]. If allocation really does not finish like the comment
> describing the timeout feared, just let the user cancel it.
> 
> Also note that when restoring a PBS backup, there is no timeout for
> disk allocation, and there don't seem to be any user complaints yet.
> 
> The 5 second timeout for receiving the config from vma is kept,
> because certain corruptions in the VMA header can lead to the
> operation hanging there.
> 
> There is no need for the $tmp variable before setting back the old
> timeout, because that is at least one second, so we'll always be able
> to set the $oldtimeout variable to undef in time in practice.
> Currently, there shouldn't even be an outer timeout in the first
> place, because the only call path leading to here is via the create
> API (also used by qmrestore), both of which don't set a timeout.
> 
> [0]: https://forum.proxmox.com/threads/126825/
> [1]: https://forum.proxmox.com/threads/128093/
> 
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
>   PVE/QemuServer.pm | 9 +++------
>   1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index bf1de179..05283562 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -7483,14 +7483,11 @@ sub restore_vma_archive {
>   		$devinfo->{$devname} = { size => $size, dev_id => $dev_id };
>   	    } elsif ($line =~ m/^CTIME: /) {
>   		# we correctly received the vma config, so we can disable
> -		# the timeout now for disk allocation (set to 10 minutes, so
> -		# that we always timeout if something goes wrong)
> -		alarm(600);
> +		# the timeout now for disk allocation
> +		alarm($oldtimeout || 0);
> +		$oldtimeout = undef;


this part looks wrong to me, because AFAIU you want to disable the timeout
(by canceling the alarm), but what you do here is to set it to $oldtimeout
if that was set before?

i guess what we want to do here is:

----
alarm(0);
<... do stuff ...>
alarm($oldtimeout || 0);
$oldtimeout = undef;
----

?


>   		&$print_devmap();
>   		print $fifofh "done\n";
> -		my $tmp = $oldtimeout || 0;
> -		$oldtimeout = undef;
> -		alarm($tmp);
>   		close($fifofh);
>   		$fifofh = undef;
>   	    }