linux-kernel - Re: [Virtio-fs] [PATCH 00/18] virtiofs: Fix various races and cleanups round 1

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Date:   Tue, 10 Sep 2019 07:52:14 +0800
From:   piaojun <piaojun@...wei.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>
CC:     Miklos Szeredi <miklos@...redi.hu>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        <linux-kernel@...r.kernel.org>, <virtio-fs@...hat.com>,
        <linux-fsdevel@...r.kernel.org>,
        <virtualization@...ts.linux-foundation.org>,
        Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [Virtio-fs] [PATCH 00/18] virtiofs: Fix various races and
 cleanups round 1



On 2019/9/10 0:14, Stefan Hajnoczi wrote:
> On Sun, Sep 08, 2019 at 07:53:55PM +0800, piaojun wrote:
>>
>>
>> On 2019/9/6 19:52, Miklos Szeredi wrote:
>>> On Fri, Sep 6, 2019 at 12:36 PM Stefan Hajnoczi <stefanha@...hat.com> wrote:
>>>>
>>>> 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@...hat.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#virtiofs-v4
>>>>>>
>>>>>> I have tested these patches with mount/umount and device removal using
>>>>>> 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.
>>>
>>> Can you give an example use case?
>>
>> 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?

Agreed, migration support is necessary for user, and hot
plugging/unplugging is also common for virtio device.

Jun