Re: [Qemu-devel] qemu-img needs "-O host_device" describing

[Kevin Wolf]

Am 30.09.2009 23:27, schrieb Adrian Bridgett:
> I've been trying to convert some personal KVM qemu (raw) file images
> to raw LVs using kvm-img -O raw.  There's a short version and long
> version of this tale.
> 
> The short version is "here is a patch to add '-O host_device' to the
> manpage", perhaps we should also warn if "kvm-img convert -O raw" is
> used on a block device (or even just automatically use host_device?)
> 
> The long version is that first of all I changed block/raw-posix.c so
> that it didn't try and ftruncat() block devices and then eventually
> tracked down why "kvm-img convert -O raw" fails to block devices (it
> seeks past holes effectively which is good on files, but not block
> devices).

What is the result of this patch? Will raw instead of host_device work
without an error message for devices? If so, I'm against the change.
It's dangerous: qemu-img would leave zero blocks unchanged instead of
overwriting them with zeros, silently corrupting the converted data.

> Digging a bit deeper I found reference to "host_device" type and it
> turns out that using that as an output format fixes both these issues
> - with only one buglet - a hopefully irrelevant error:
> 
>   kvm-img convert -O host_device /var/lib/vm/bishop-disk 
> /dev/rootvg/bishop-disk 
>   Unknown option 'size'

Yes, this is a bug in the host_device definition. I'll send a fix.

Your documentation fix looks fine. Can you resubmit it in a new
(top-level) mail with [PATCH] in its subject and a Signed-off-by line in
it? Only this way the maintainers will pick it up.

Kevin