Re: [PATCH 1/2] tcm_vhost: Wait for pending requests in vhost_scsi_flush()

[Asias He <asias@redhat.com>]

On Mon, Mar 11, 2013 at 01:53:56PM +0200, Michael S. Tsirkin wrote:
> On Mon, Mar 11, 2013 at 12:36:37PM +0100, Paolo Bonzini wrote:
> > Il 11/03/2013 06:09, Asias He ha scritto:
> > > This patch makes vhost_scsi_flush() wait for all the pending requests
> > > issued before the flush operation to be finished.
> > 
> > There is no protection against issuing concurrent flush operations.  If
> > we later would like to make the flush a ioctl (for example for migration
> > purposes),
> 
> For migration I think we need to stop vhost, flush isn't useful
> if we keep submitting requests afterwards.
> 
> > it would be confusing, and I'm not sure how you could extend
> > the during_flush machinery.
> > 
> > What about making vhost_scsi_flush() wait for all pending requests,
> > including those issues during the flush operation?  Then you can easily
> > support concurrent flushes; just add a waitqueue and wake_up_all at the
> > end of the flush operation.
> > 
> > BTW, adding such a ioctl as part of this patch would probably be a good
> > thing to do anyway.
> > 
> > Paolo
> 
> Please keep it separate, it's painful enough that we have a driver
> with to established userspace, I don't want to add ioctls
> until it's used by some upstream.

Let's add the ioctls later.

> -- 
> MST

-- 
Asias