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Date:   Mon, 9 Sep 2019 18:14:55 +0200
From:   Stefan Hajnoczi <stefanha@redhat.com>
To:     piaojun <piaojun@huawei.com>
Cc:     Miklos Szeredi <miklos@szeredi.hu>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        linux-kernel@vger.kernel.org, virtio-fs@redhat.com,
        linux-fsdevel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [Virtio-fs] [PATCH 00/18] virtiofs: Fix various races and
 cleanups round 1
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On Sun, Sep 08, 2019 at 07:53:55PM +0800, piaojun wrote:
>=20
>=20
> On 2019/9/6 19:52, Miklos Szeredi wrote:
> > On Fri, Sep 6, 2019 at 12:36 PM Stefan Hajnoczi <stefanha@redhat.com> w=
rote:
> >>
> >> On Fri, Sep 06, 2019 at 10:15:14AM +0200, Miklos Szeredi wrote:
> >>> On Thu, Sep 5, 2019 at 9:49 PM Vivek Goyal <vgoyal@redhat.com> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> Michael Tsirkin pointed out issues w.r.t various locking related TODO
> >>>> items and races w.r.t device removal.
> >>>>
> >>>> In this first round of cleanups, I have taken care of most pressing
> >>>> issues.
> >>>>
> >>>> These patches apply on top of following.
> >>>>
> >>>> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git#virt=
iofs-v4
> >>>>
> >>>> I have tested these patches with mount/umount and device removal usi=
ng
> >>>> qemu monitor. For example.
> >>>
> >>> Is device removal mandatory?  Can't this be made a non-removable
> >>> device?  Is there a good reason why removing the virtio-fs device
> >>> makes sense?
> >>
> >> Hot plugging and unplugging virtio PCI adapters is common.  I'd very
> >> much like removal to work from the beginning.
> >=20
> > Can you give an example use case?
>=20
> I think VirtFS migration need hot plugging, or it may cause QEMU crash
> or some problems.

Live migration is currently unsupported.  Hot unplugging the virtio-fs
device would allow the guest to live migrate successfully, so it's a
useful feature to work around the missing live migration support.

Is this what you mean?

Stefan

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