Re: problem about changing state to XenbusStateClosed resulting in vbd entry removed from xenstore

[Max Zhen <Max.Zhen@Sun.COM>]

>>+ Is there any other way to flush all the I/O to the disk?
>>Currently, the only way to flush the I/Os is to change the frontend
>>state to XenbusStateClosed.
>>Since changing the state to XenbusStateClosed is a dangerous thing to do
>>(cause all the vbd interface information to be removed), I cannot just
>>flush the I/O, while keep the frontend and backend connected.
>>Could there be any new state or command to do that?
>>    
>>
>
>A block-detach should be switching the backend to XenbusStateClosing, which
>the frontend will observe, allowing it to flush remaining I/O.  Only when the
>frontend is done should it switch to Closed, which will then be seen by the
>backend and then the backend can finish up and close itself.
>
>Are you not seeing this?
>  
>
Yes, I've seen this.
But, the key point is that how to flush the I/O without disconnecting 
between frontend and backend.
It seems to me that I/O flushing is more like a command, say, 
BLKIF_OP_FLUSH, than changing the driver to various states, especially 
XenbusStateClosing/Closed.

Any idea?

Thanks,
Max

>Cheers,
>
>Ewan.
>  
>