From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5BF56C4740A for ; Mon, 9 Sep 2019 23:52:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 39EF620674 for ; Mon, 9 Sep 2019 23:52:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731115AbfIIXwT (ORCPT ); Mon, 9 Sep 2019 19:52:19 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:2254 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730370AbfIIXwT (ORCPT ); Mon, 9 Sep 2019 19:52:19 -0400 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 16035839126179043B18; Tue, 10 Sep 2019 07:52:17 +0800 (CST) Received: from [10.177.253.249] (10.177.253.249) by smtp.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.439.0; Tue, 10 Sep 2019 07:52:15 +0800 Subject: Re: [Virtio-fs] [PATCH 00/18] virtiofs: Fix various races and cleanups round 1 To: Stefan Hajnoczi References: <20190905194859.16219-1-vgoyal@redhat.com> <20190906103613.GH5900@stefanha-x1.localdomain> <866a1469-2c4b-59ce-cf3f-32f65e861b99@huawei.com> <20190909161455.GG20875@stefanha-x1.localdomain> CC: Miklos Szeredi , "Michael S. Tsirkin" , , , , , Vivek Goyal From: piaojun Message-ID: <5D76E5AE.3090006@huawei.com> Date: Tue, 10 Sep 2019 07:52:14 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20190909161455.GG20875@stefanha-x1.localdomain> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.253.249] X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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 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 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