From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 1/2] tcm_vhost: Wait for pending requests in
	vhost_scsi_flush()
Date: Mon, 11 Mar 2013 13:53:56 +0200
Message-ID: <20130311115356.GD23359@redhat.com>
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, target-devel@vger.kernel.org, Stefan Hajnoczi <stefanha@redhat.com>
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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.

-- 
MST