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Date: Thu, 31 Jan 2019 15:25:02 +0000
From: Anthony PERARD <anthony.perard@citrix.com>
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Subject: Re: [Qemu-devel] [PATCH v2] xen-block: handle resize callback
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To: Paul Durrant <Paul.Durrant@citrix.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "qemu-block@nongnu.org" <qemu-block@nongnu.org>, "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>, Stefan Hajnoczi <stefanha@redhat.com>, Stefano Stabellini <sstabellini@kernel.org>, Kevin Wolf <kwolf@redhat.com>, Max Reitz <mreitz@redhat.com>

On Thu, Jan 31, 2019 at 03:22:18PM +0000, Paul Durrant wrote:
> > -----Original Message-----
> > From: Anthony PERARD [mailto:anthony.perard@citrix.com]
> > Sent: 31 January 2019 15:21
> > To: Paul Durrant <Paul.Durrant@citrix.com>
> > Cc: qemu-devel@nongnu.org; qemu-block@nongnu.org; xen-
> > devel@lists.xenproject.org; Stefan Hajnoczi <stefanha@redhat.com>; Stefano
> > Stabellini <sstabellini@kernel.org>; Kevin Wolf <kwolf@redhat.com>; Max
> > Reitz <mreitz@redhat.com>
> > Subject: Re: [PATCH v2] xen-block: handle resize callback
> > 
> > On Wed, Jan 30, 2019 at 04:19:48PM +0000, Paul Durrant wrote:
> > > Some frontend drivers will handle dynamic resizing of PV disks, so set
> > up
> > > the BlockDevOps resize_cb() method during xen_block_realize() to allow
> > > this to be done.
> > >
> > > Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> > > ---
> > 
> > 
> > > +    /*
> > > +     * Mimic the behaviour of Linux xen-blkback and re-write the state
> > > +     * to trigger the frontend watch.
> > > +     */
> > > +    xen_device_backend_set_state(xendev, backend_state);
> > 
> > :(, that function doesn't write the state again if it hasn't changed.
> > So in my testing, Linux never did anything.
> 
> Gah! I forgot about that. Alright, it's going to have to be a bit more crude.

more crude > Yes, I tried to ignore the check in _set_state and end-up
with an infinit loop.

-- 
Anthony PERARD