Re: [Qemu-devel] [PATCH] qcow2: Add full image preallocation option

[Stefan Hajnoczi]

On Thu, Jan 27, 2011 at 11:45:55AM -0600, Anthony Liguori wrote:
> On 01/27/2011 09:52 AM, Kevin Wolf wrote:
> >This adds a preallocation=full mode to qcow2 image creation, which does not
> >only allocate metadata for the whole image, but also writes zeros to it,
> >creating a non-sparse image file.
> 
> The writing zeros bit is in order to support physical devices?
> Would it be better to have a flag in BlockDriverState that indicated
> whether uninitialized sectors could be assumed to be zero filled and
> key off of that?

There is already:
int bdrv_has_zero_init(BlockDriverState *bs);

Stefan