On 09/13/2011 09:54 AM, Alex Bligh wrote:
> Paolo,
>
> --On 13 September 2011 09:49:01 +0200 Paolo Bonzini
> <[email protected]> wrote:
>
>> On 09/13/2011 09:47 AM, Folkert van Heusden wrote:
>>>> It might be a good way to get a flags-passing mechanism acceptable to
>>>> > Paul et al ready.
>>> Will that change the protocol-handshake as currently implemented? E.g.
>>> the 4 bytes with flags.
>>
>> No, it's only in the kernel module side. I think Paul in the end agreed
>> about a new ioctl when I posted my TRIM patches to LKML.
>
> Unless I'm missing something (quite possible):
>
> 1. The kernel module must not send TRIM requests to a server unless the
> server can accept them.
>
> 2. Therefore the server must advertise it can support TRIM (somehow). This
> requires a userspace change to the server.
>
> 3. As the negotiation is carried out by the userspace client, the userspace
> client must support that negotiation, as well as make the ioctl() to
> the kernel to turn (1) above on and off. That's a userspace change to
> the client.
>
> These are pretty minor (or in the case of (2) non-existent if you aren't
> actually supporting TRIM on the default server), but still need to be
> done I think.

Yeah, I misunderstood what Folkert wrote (or at least I wasn't clear 
enough).  The protocol doesn't change, but just like FLUSH+FUA there is 
an additional flags bit that the server must set in order to enable the 
feature.

Paolo


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