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Re: [Qemu-devel] [PATCH v2 3/3] block: Introduce BlockDriver.requires_gr
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v2 3/3] block: Introduce BlockDriver.requires_growing_file |
Date: |
Thu, 19 Mar 2015 14:18:46 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 |
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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