Re: [Nbd] Question about the expected behaviour of nbd-server for async ops

[Goswin von Brederlow <goswin-v-b@...186...>]

Alex Bligh <alex@...872...> writes:

> --On 30 May 2011 14:13:04 +0200 Goswin von Brederlow
> <goswin-v-b@...186...> wrote:
>
>>> I don't think that not supporting extremely large requests is going to
>>> be a problem in practice, providing we return a proper error code.
>>
>> Maybe there should be an option field for this so client and server can
>> agree on a reasonable size. The client MUST then split larger requests
>> into smaller chunks.
>
> Note you will need to fix the kernel module (I think) if you want to limit
> the maximum size of a request. I am not aware of any current limit
> on the size of a request (other than 2^32 bytes).

Indeed. If the protocol has the feature to query the maximum request
size then the kernel will need a new ioctl to pass that to the nbd modul
and the nbd module will need some logic to split requests.

But as Wouter says it is a verry rare problem so there is no hurry to
implement this right away. But since it does seem to happen in some
situations I think it should be considered in the protocol.

MfG
        Goswin