Re: [Qemu-devel] qemu-img convert with block driver without .bdrv_create (like iscsi)

[ronnie sahlberg]

On Thu, Oct 25, 2012 at 1:02 AM, Kevin Wolf <address@hidden> wrote:
> Am 25.10.2012 09:52, schrieb Paolo Bonzini:
>> Il 25/10/2012 09:46, Kevin Wolf ha scritto:
>>>>> 1)add a .bdrv_create in block/iscsi.c ?
>>>>>
>>>>> (like host_device block driver, only open/close the device and check if 
>>>>> size if big enough)
>>> Yes, this is the right way.
>>
>> Could it be a default implementation of .bdrv_create (i.e. something
>> you'd do in bdrv_create if the protocol doesn't have it)?
>
> No, there are block drivers that really can't create images. They should
> keep failing.

Technically, you can not create new LUNs via the iscsi protocol
itself, you can only access pre-existing luns
that have been created by some out-of-band method.

So basically, with iscsi you can only ever access already preexisting luns.

In that case I think requiring a .bdrv_create feels wrong. We are not
creating a new LUN here but just opening an already existing LUN.


What about changing bdrv_create() so that IF there is no .bdrv_create
method, then assume it might be a pre-existing file in which case we
fallback to use .bdrv_open instead.

regards
ronnie sahlberg