Re: [Xen-devel] problem about changing state to XenbusStateClosed resulting in vbd entry removed from xenstore

[Max Zhen <Max.Zhen@xxxxxxx>]

> > + 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.
>  
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