Re: [PATCH v2 1/2] qcow2: Force preallocation with data-file-raw

[Eric Blake]

On 3/26/21 9:55 AM, Max Reitz wrote:
> Setting the qcow2 data-file-raw bit means that you can ignore the
> qcow2 metadata when reading from the external data file.  It does not
> mean that you have to ignore it, though.  Therefore, the data read must
> be the same regardless of whether you interpret the metadata or whether
> you ignore it, and thus the L1/L2 tables must all be present and give a
> 1:1 mapping.
> 
> This patch changes 244's output: First, the qcow2 file is larger right
> after creation, because of metadata preallocation.  Second, the qemu-img
> map output changes: Everything that was not explicitly discarded or
> zeroed is now a data area.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2.c              | 34 ++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/244.out |  9 ++++-----
>  2 files changed, 38 insertions(+), 5 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

I think this counts as a bug fix worthy of inclusion in 6.0.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org