Re: [Qemu-devel] [PATCH] qemu-io: add flag to mark files growable

[Kevin Wolf <kwolf@redhat.com>]

Christoph Hellwig schrieb:
> On Mon, Jul 06, 2009 at 12:40:06PM +0200, Kevin Wolf wrote:
>> Ok, you are right. raw was the only exception because it could be used
>> as a protocol even though it didn't have a protocol name.
>>
>> Looks fine to me then if you enforce the limitation instead of only
>> printing an error message and opening the image anyway. Not printing the
>> error and opening the image would be fine either. I just don't like
>> error messages without errors.
> 
> Well, the primary use of qemu-iotests is to try out the I/O patterns,
> and the -g option is to check out we do the correct thing for growable
> files, so I'd really prefer it to fail if we're not allow to actually
> make it growable.

Perfectly reasonable. But then make it really fail.

> Now one think I could do is to just add a growable flag to the
> BlockDriver to make it explicit.  Currently only raw files (in the posix
> and win32 flavours) would set it.

Good point actually, your current logic is wrong: raw-win32 doesn't have
the file protocol. I'm not sure though if introducing a new flag just
for qemu-io is right. After all qemu-io should test what the drivers
provide to qemu and not extend them to work with qemu-io. Currently the
drivers don't have the concept of non-growable images.

>  That would also fix the bug what we
> currenly allow to grow host devices even if we can't.

How that? The host device drivers don't have a protocol name, do they?

Kevin