Re: [Qemu-devel] RFC: raw device support for block device targets

[Kevin Wolf <kwolf@redhat.com>]

Am 11.12.2011 11:45, schrieb Alex Bligh:
> 
> 
> --On 8 December 2011 13:40:57 +0100 Kevin Wolf <kwolf@redhat.com> wrote:
> 
>>> qemu-img convert appears to support block devices as input, but not
>>> as output. That is irritating, as when using qemu-img convert to
>>> convert qcow to raw on a block partition, an intermediate file has
>>> to be used, which slows things down and pointlessly uses disk space.
>>>
>>> The problem is that ftruncate() is being called on the output file
>>> in order ensure it is sufficiently large, and this fails on
>>> block devices.
> ...
>>
>> Creating an image on a block device shouldn't even call raw_create(),
>> but only hdev_create(), which doesn't try to truncate the device, but
>> just uses lseek to make sure that it's large enough.
>>
>> Which qemu version are you using and what's your command line?
> 
> I was testing on:
> 
> amb@alex-test:~$ qemu-img --version
> qemu-img version 0.12.3, Copyright (c) 2004-2008 Fabrice Bellard

That's the problem. It should work since 0.13.

Kevin