Re: [Qemu-block] [Qemu-devel] [PATCH v2 3/3] block: Introduce BlockDriver.requires_growing_file

[Eric Blake]

On 03/19/2015 01:03 PM, Max Reitz wrote:
> This flag is set if write accesses to BDSs managed by the respective
> driver may lead to writes beyond the end of the underlying file BDS,
> expecting it to increase its size accordingly.
> 
> This behavior, however, is only supported by protocol BDSs having the
> BDS.growing flag set. If they do not, emit a warning.
> 
> An example of such a misconfiguration is exporting a qcow2 file using
> the reference NBD server implementation, which cannot interpret the
> qcow2 format and will thus expose it directly over the network. When
> accessing that export with qemu, qemu's qcow2 driver may try to allocate
> clusters over the NBD connection, writing to addresses beyond the size
> of the NBD export, which will then fail (without the user knowing why,
> without this warning).
> 
> Signed-off-by: Max Reitz <address@hidden>
> ---
>  block.c                   | 16 ++++++++++++++++
>  block/qcow.c              |  1 +
>  block/qcow2.c             |  2 ++
>  block/qed.c               |  1 +
>  block/vdi.c               |  2 ++
>  block/vhdx.c              |  2 ++
>  block/vmdk.c              |  1 +
>  block/vpc.c               |  2 ++
>  include/block/block_int.h |  4 ++++
>  9 files changed, 31 insertions(+)
> 

Reviewed-by: Eric Blake <address@hidden>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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