Re: [Qemu-block] [Qemu-devel] [PATCH] raw-posix: add 'offset' and 'size' options

[Eric Blake]

On 10/04/2016 04:15 AM, Daniel P. Berrange wrote:
> On Tue, Oct 04, 2016 at 10:57:49AM +0200, Kevin Wolf wrote:
>> Am 03.10.2016 um 13:07 hat Tomáš Golembiovský geschrieben:
>>>>>>> +    if (((bs->drv != &bdrv_file) || !bs->read_only) &&    
>>>>>>
>>>>>> Why the check against bdrv_file ?  
>>>>>
>>>>> To limit it only to files. Maybe there is better way to do that? The
>>>>> devices have a nasty habit to change the size. Sure, this can happen to
>>>>> file too, e.g. if somebody truncates the file outside QEMU. But that's
>>>>> rather a bad behaviour. For devices changing the size may be perfectly
>>>>> valid operation, e.g. replacing CD in drive or card in a card reader.  
>>>>
>>>> The raw driver is usable over any storage backend (file, rbd, iscsi,
>>>> etc, etc) and it is valid to want to use a offset/size parameter in
>>>> combination with any of them. So we should not restrict it to just
>>>> files.
>>
>> Just to clear up some confusion here: There are the file/host_device/...
>> protocol drivers, which only access local files. These are implemented
>> in raw-posix.c, i.e. the file that this patch is touching. raw-win32.c
>> implements the same kind of file access for Windows.
> 
> This naming is constantly confusing - is there any appetite for renaming
> those to 'file-posix.c' and 'file-win32.c', and raw_bsd.c to raw.c ?

I would welcome that naming change.  The mix of - vs. _ is bad enough;
and _bsd makes me think BSD (non-Linux) rather than shared block device
code.

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

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