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Date: Fri, 5 Dec 2014 09:35:38 -0500
From: Jeff Cody <jcody@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] vhdx: Return true for bdrv_has_zero_init
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To: Kevin Wolf <kwolf@redhat.com>
Cc: amulya.lokesha@emc.com, qemu-devel@nongnu.org, stefanha@redhat.com, mreitz@redhat.com

On Fri, Dec 05, 2014 at 12:07:19PM +0100, Kevin Wolf wrote:
> Am 05.12.2014 um 11:26 hat Kevin Wolf geschrieben:
> > Like for most other image formats, vhdx images read as all zero in qemu
> > after their creation (we're taking advantage from the fact that qemu has
> > just created the image, because PAYLOAD_BLOCK_NOT_PRESENT actually means
> > undefined rather than zeroed according to the spec).
> 
> Brain fart, self-NACK.
> 
> This obviously means that 'qemu-img convert' still can't leave zeros in
> the source file unwritten in the destination, otherwise we're corrupting
> data. qemu would still read them correctly, but other implementations
> might not.
> 
> We'd have to write the BAT for dynamic images with PAYLOAD_BLOCK_ZERO
> for all clusters before we can make this change.
> 
> Jeff, do you want to fix this?
>

Yes, I'll go ahead and put together a patch(es) for that.