Re: [pve-devel] [PATCH storage] plugin: file size info: use fallback for actual size

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 28/11/2022 um 16:55 schrieb Fiona Ebner:
> The actual-size property is an optional property in the QAPI
> definition for ImageInfo. If it's not set, simply use the information
> from stat() as a fallback. This is essentially the same
> raw_get_allocated_file_size() in QEMU does anyways.
> 
> Reported in the community forum:
> https://forum.proxmox.com/threads/118443/post-513421
> 
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
> 
> Thanks to Mira for setting up a GlusterFS instance and discussing the
> issue with me!
> 
> I'm not sure why QEMU fails here, didn't see much that could go wrong
> beside the fstat() call failing. But our stat() call in the beginning
> of file_size_info already succeeded at that point :/ The mysteries of
> QEMU+GlusterFS.
> 
> Also, it's a bit strange to call qemu-img info regardless of whether
> the image is a VM image or not. E.g., this results in the format
> property for backups to always be raw, rather than the backup format.
> Should we change that (for 8.0)?
> 
>  PVE/Storage/Plugin.pm | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
> index 8a41df1..7773ac3 100644
> --- a/PVE/Storage/Plugin.pm
> +++ b/PVE/Storage/Plugin.pm
> @@ -899,6 +899,7 @@ sub file_size_info {
>      }
>  
>      my ($size, $format, $used, $parent) = $info->@{qw(virtual-size format actual-size backing-filename)};
> +    $used ||= $st->blocks * 512;

in general OK, but can we really be sure that blocks are always 512 bytes?

>  
>      ($size) = ($size =~ /^(\d+)$/) or die "size '$size' not an integer\n"; # untaint
>      # coerce back from string