[pve-devel] [PATCH v2 qemu-server] add check to resize disk if current size could not be determined

[Thomas Lamprecht]

On 09.09.19 12:39, Tim Marx wrote:
> This check ensures that disks aren't unintentionally shrunken, if the
> size is zero due to an underlying problem.
> ---
> * fix indentation
> 
>  PVE/API2/Qemu.pm | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/PVE/API2/Qemu.pm b/PVE/API2/Qemu.pm
> index 245de80..e6f3cce 100644
> --- a/PVE/API2/Qemu.pm
> +++ b/PVE/API2/Qemu.pm
> @@ -3511,6 +3511,8 @@ __PACKAGE__->register_method({
>  	    PVE::Storage::activate_volumes($storecfg, [$volid]);
>  	    my $size = PVE::Storage::volume_size_info($storecfg, $volid, 5);
> 
> +	    die "volume $volid does not exists\n" if !$size;

Hmm, but I _can_ create a 0 size disk image:

# qemu-img create -f qcow2 test.qcow2 0
Formatting 'test.qcow2', fmt=qcow2 size=0 cluster_size=65536 lazy_refcounts=off refcount_bits=16
# qemu-img info test.qcow2
image: test.qcow2
file format: qcow2
virtual size: 0 (0 bytes)
disk size: 192K
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false


while a bit strange, it's possible and the single real use case I'd then
have would be to resize it to some actual positive value.. Also ".. does
not exists" is then not true.

How about: parse stderr in qemu.img info too, with that you should be
able to check if a file really does not exists (`qemu-img info` does not
exits with <> 0 in that case but prints on stderr) and if not then set
$size and $used to undef? Then we can do a defined-ness check here...