Re: [Qemu-devel] [PATCH] [UPDATED] Add host_device support to qemu-img.

[Anthony Liguori <aliguori@us.ibm.com>]

Nolan wrote:
> This patch allows the use a host_device as the destination for "qemu-img
> convert".
>
> I added a ->bdrv_create function host_device.  It merely verifies that
> the device exists and is large enough.
>
> A check is needed in the qemu-img convert loop to ensure that we write
> out all 0 sectors to the host_device.  Otherwise they end up with stale
> garbage where all zero sectors were expected.
>
> I also made the check against bdrv_is_allocated enabled for everything
> _except_ host devices, since there is no point in making the block
> backend write a bunch of zeros just so that we can memcmp them
> immediately afterwards.  Host devices can't benefit from this because
> there is no way to differentiate between a sector being unallocated
> because it was never written, or because it was written with all zeros
> and then made a trip through qemu-img convert.
>
> Finally, there is an unrelated fix for a typo in the error message
> printed if the destination device does not support ->bdrv_create.
>
> Signed-off-by: Nolan Leake <nolan <at> sigbus.net>
>   
Applied.  Thanks.

Regards,

Anthony Liguori