Re: [Qemu-devel] [PATCH 0/4] block: Warn about usage of growing formats over non-growable protocols

[Max Reitz <mreitz@redhat.com>]

On 12.07.2014 00:23, Max Reitz wrote:
> Some image formats (e.g. qcow2) require the underlying file to grow on
> write accesses, but this is in fact not supported by all protocols (e.g.
> nbd does not). If such a format requiring file growth is used
> non-read-only over a protocol which does not support this, a warning
> should be issued.
>
> This warning is issued for example whenever one tries to export a qcow2
> image over nbd-server and use the export from qemu.
>
> We could make this an error, but I decided not to in order to retain
> "compatibility" (although if this warning is emitted, the user should
> have already complained about I/O errors on write accesses, so it's
> questionable what behavior this should be compatible to).
>
> While at it, make BDS.growable actually indicate what it is (as far as I
> understood) supposed to: Whether the BDS supports writes beyond the end
> of the disk size (which then automatically increase that disk size).
>
>
> Max Reitz (4):
>    block: Correct bs->growable
>    block: Introduce requires_growing_file
>    iotests: Make some qemu-io commands read-only
>    iotests: Skip read and write in 040 for length=0
>
>   block.c                    | 11 +++++++++++
>   block/blkdebug.c           |  2 ++
>   block/blkverify.c          |  2 ++
>   block/cow.c                |  1 +
>   block/iscsi.c              |  2 ++
>   block/nbd.c                |  2 ++
>   block/qcow.c               |  1 +
>   block/qcow2.c              |  2 ++
>   block/qed.c                |  1 +
>   block/raw_bsd.c            |  1 +
>   block/vdi.c                |  2 ++
>   block/vhdx.c               |  2 ++
>   block/vmdk.c               |  1 +
>   block/vpc.c                |  2 ++
>   include/block/block_int.h  |  4 ++++
>   tests/qemu-iotests/040     | 18 +++++++++++-------
>   tests/qemu-iotests/072     |  9 ++++++++-
>   tests/qemu-iotests/072.out |  1 +
>   tests/qemu-iotests/089     |  2 +-
>   19 files changed, 57 insertions(+), 9 deletions(-)

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