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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 38403C4740A for ; Mon, 9 Sep 2019 16:18:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18F4621920 for ; Mon, 9 Sep 2019 16:18:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388889AbfIIQSW (ORCPT ); Mon, 9 Sep 2019 12:18:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60264 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388828AbfIIQSV (ORCPT ); Mon, 9 Sep 2019 12:18:21 -0400 Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 87B89155DB for ; Mon, 9 Sep 2019 16:18:21 +0000 (UTC) Received: by mail-qk1-f199.google.com with SMTP id t26so16971360qkt.0 for ; Mon, 09 Sep 2019 09:18:21 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=xd5J0j1O8RM23sIIIj9h2xCJg8OqHfg7OWxpv2iexsc=; b=nqmr2ChURNValWE59O90cwF7CRoCCwijyx3xqJj0RbAud5v6M6gZiSB3ixuArwBFPv JfeYhPvKzoHrxRa3737keER/aEqb7vz30ZBBKmgYnbtzEj6HChW+WAJOKsu9xox9Nwp7 R7FUeshMQEfXWP4rsGQwCmOs2nsitdbJ6tzCooDS4IL8c0w9+eJdvueYxyvStCX5Eqp/ uk0IGeO/5LoyHAie0DSVXHVzwQfJULUEwlHb84tsDM7UMglEwywJioJ38vkl2/WA0MKA msEijPq3jPq+BN50/LvCqOX670QNN4iz2Jn0t1zXKzLUpAgIfw5xE1rHRj8cY4meZvDm lQPg== X-Gm-Message-State: APjAAAVSj8BANpSgt9E323TrFx1JC0oif752DDpEZ25+JKOD7sdxm2vB Lb4sW/bfoVJXAbDDM39XeBanRUczKH68815I+h928mHtJ5/cyIn5zAT7Ps4hK1JRS9bvVLKPl8Z essLwEYT6kpVVDNBfmcwytvZWzA== X-Received: by 2002:aed:316d:: with SMTP id 100mr442786qtg.20.1568045900873; Mon, 09 Sep 2019 09:18:20 -0700 (PDT) X-Google-Smtp-Source: APXvYqxvZ3BxEyb3pt+fbqjr5qKBJvhxJopIJiuMLcQ+RPNA0muqjQbM1NQBmU9ZKN8evHR3WQQZoA== X-Received: by 2002:aed:316d:: with SMTP id 100mr442761qtg.20.1568045900648; Mon, 09 Sep 2019 09:18:20 -0700 (PDT) Received: from redhat.com ([80.74.107.118]) by smtp.gmail.com with ESMTPSA id c14sm8927771qta.80.2019.09.09.09.18.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Sep 2019 09:18:19 -0700 (PDT) Date: Mon, 9 Sep 2019 12:18:13 -0400 From: "Michael S. Tsirkin" To: Stefan Hajnoczi Cc: piaojun , Miklos Szeredi , linux-kernel@vger.kernel.org, virtio-fs@redhat.com, linux-fsdevel@vger.kernel.org, virtualization@lists.linux-foundation.org, Vivek Goyal Subject: Re: [Virtio-fs] [PATCH 00/18] virtiofs: Fix various races and cleanups round 1 Message-ID: <20190909121604-mutt-send-email-mst@kernel.org> References: <20190905194859.16219-1-vgoyal@redhat.com> <20190906103613.GH5900@stefanha-x1.localdomain> <866a1469-2c4b-59ce-cf3f-32f65e861b99@huawei.com> <20190909161455.GG20875@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190909161455.GG20875@stefanha-x1.localdomain> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Sep 09, 2019 at 06:14:55PM +0200, 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? > > Stefan Exactly. That's what I also said. To add to that, hotplug can not be negotiated, so it's not a feature we can easily add down the road if old guests crash on unplug. Thus a driver that does not support unplug should not claim to support removal. -- MST