Re: [Qemu-devel] [PATCH 2/2] qemu-nbd: Add --image-size option

[Paolo Bonzini]

On 20/09/2016 13:12, Daniel P. Berrange wrote:
> On Tue, Sep 20, 2016 at 11:59:28AM +0200, Paolo Bonzini wrote:
>>
>>
>> On 20/09/2016 11:41, Tomáš Golembiovský wrote:
>>> When image is part of the file it makes sense to limit the length of the
>>> image in the file. Otherwise it is assumed that the image spans to the
>>> end of the file. This assumption may lead to reads/writes outside of the
>>> image and thus lead to errors or data corruption.
>>>
>>> To limit the assumed image size new option is introduced.
>>
>> The patch makes sense, but I think the commit message is incorrect
>> because this bug is already fixed by patch 1.  Also, the option in the
>> help is --device-size, not --image-size; I would just call it --size.
> 
> I don't think it makes sense as a special case in qemu-nbd.
> 
> It feels like this is better done by extending the 'raw'
> block driver with 'offset' and 'length' parameters. You
> can then layer the 'raw' block driver over any existing
> QEMU blocker driver, anywhere in QEMU / tools that accept
> a block device description. No need to add extra parameters
> to any of the programs.

This makes sense too (and then --offset and partitions can be
implemented on top).

Paolo