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

[Adrian Bridgett]

On Thu, Oct  1, 2009 at 11:57:02 +0200 (+0200), Kevin Wolf wrote:
> Am 30.09.2009 23:27, schrieb Adrian Bridgett:
[snip]
> > 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.

Yep - that's exactly what happens - I was going to send a subsequent
one to stop qemu-img convert from skipping past unallocated blocks -
but then found the host_device format and that sorted it all out,
sorry if that wasn't clear.  I do wonder if -O raw should warn when
run against output devices which aren't regular files though.

> 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.

Absolutely, thanks for the help :-)

Adrian
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