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From: Miklos Szeredi <miklos@szeredi.hu>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
	linux-fsdevel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, virtio-fs@redhat.com,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 00/18] virtiofs: Fix various races and cleanups round 1
Date: Fri, 6 Sep 2019 15:55:21 +0200	[thread overview]
Message-ID: <CAJfpegsL4PLvROr58vtjmyvQu-F17X3xoKCztP2H0fog0xUXhA@mail.gmail.com> (raw)
In-Reply-To: <20190906120817.GA22083@redhat.com>

On Fri, Sep 6, 2019 at 2:08 PM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> On Fri, Sep 06, 2019 at 01:52:41PM +0200, Miklos Szeredi wrote:
> > On Fri, Sep 6, 2019 at 12:36 PM Stefan Hajnoczi <stefanha@redhat.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@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#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?
>
> David Gilbert mentioned this could be useful if daemon stops responding
> or dies. One could remove device. That will fail all future requests
> and allow unmounting filesystem.
>
> Havind said that, current implementation will help in above situation
> only if there are no pending requests. If there are pending requests
> and daemon stops responding, then removal will hang too, as we wait
> for draining the queues.
>
> So at some point of time, we also need some sort of timeout functionality
> where we end requests with error after a timeout.
>
> I feel we should support removing device at some point of time. But its
> not necessarily a must have feature for first round.

If there's no compelling reason to do it in the first round, than I'd
prefer to not do it.   More complexity -> more bugs.

Thanks,
Miklos

  reply	other threads:[~2019-09-06 13:55 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-05 19:48 [PATCH 00/18] virtiofs: Fix various races and cleanups round 1 Vivek Goyal
2019-09-05 19:48 ` [PATCH 01/18] virtiofs: Remove request from processing list before calling end Vivek Goyal
2019-09-06 10:40   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 02/18] virtiofs: Check whether hiprio queue is connected at submission time Vivek Goyal
2019-09-06 10:43   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 03/18] virtiofs: Pass fsvq instead of vq as parameter to virtio_fs_enqueue_req Vivek Goyal
2019-09-06 10:44   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 04/18] virtiofs: Check connected state for VQ_REQUEST queue as well Vivek Goyal
2019-09-06 10:45   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 05/18] Maintain count of in flight requests for VQ_REQUEST queue Vivek Goyal
2019-09-06 10:46   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 06/18] virtiofs: ->remove should not clean virtiofs fuse devices Vivek Goyal
2019-09-06 10:47   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 07/18] virtiofs: Stop virtiofs queues when device is being removed Vivek Goyal
2019-09-06 10:47   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 08/18] virtiofs: Drain all pending requests during ->remove time Vivek Goyal
2019-09-06 10:52   ` Stefan Hajnoczi
2019-09-06 14:17     ` Vivek Goyal
2019-09-06 14:18       ` Michael S. Tsirkin
2019-09-09 16:10         ` Stefan Hajnoczi
2019-09-08 10:11   ` [Virtio-fs] " piaojun
2019-09-05 19:48 ` [PATCH 09/18] virtiofs: Add an helper to start all the queues Vivek Goyal
2019-09-06 10:54   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 10/18] virtiofs: Do not use device managed mem for virtio_fs and virtio_fs_vq Vivek Goyal
2019-09-06 10:56   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 11/18] virtiofs: stop and drain queues after sending DESTROY Vivek Goyal
2019-09-06 11:50   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 12/18] virtiofs: Use virtio_fs_free_devs() in error path Vivek Goyal
2019-09-06 11:51   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 13/18] virtiofs: Do not access virtqueue in request submission path Vivek Goyal
2019-09-06 11:52   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 14/18] virtiofs: Add a fuse_iqueue operation to put() reference Vivek Goyal
2019-09-06 12:00   ` Stefan Hajnoczi
2019-09-06 13:35     ` Vivek Goyal
2019-09-05 19:48 ` [PATCH 15/18] virtiofs: Make virtio_fs object refcounted Vivek Goyal
2019-09-06 12:03   ` Stefan Hajnoczi
2019-09-06 13:50     ` Vivek Goyal
2019-09-09 16:12       ` Stefan Hajnoczi
2019-09-08 11:10   ` [Virtio-fs] " piaojun
2019-09-09 15:35     ` Vivek Goyal
2019-09-05 19:48 ` [PATCH 16/18] virtiofs: Use virtio_fs_mutex for races w.r.t ->remove and mount path Vivek Goyal
2019-09-06 12:05   ` Stefan Hajnoczi
2019-09-06 13:51     ` Vivek Goyal
2019-09-09 16:13       ` Stefan Hajnoczi
2019-09-08 11:19   ` [Virtio-fs] " piaojun
2019-09-05 19:48 ` [PATCH 17/18] virtiofs: Remove TODO to quiesce/end_requests Vivek Goyal
2019-09-06 12:06   ` Stefan Hajnoczi
2019-09-05 19:48 ` [PATCH 18/18] virtiofs: Remove TODO item from virtio_fs_free_devs() Vivek Goyal
2019-09-06 12:06   ` Stefan Hajnoczi
2019-09-06  8:15 ` [PATCH 00/18] virtiofs: Fix various races and cleanups round 1 Miklos Szeredi
2019-09-06 10:36   ` Stefan Hajnoczi
2019-09-06 11:52     ` Miklos Szeredi
2019-09-06 12:08       ` Vivek Goyal
2019-09-06 13:55         ` Miklos Szeredi [this message]
2019-09-06 13:57         ` Michael S. Tsirkin
2019-09-06 14:11           ` Miklos Szeredi
2019-09-06 14:17             ` Michael S. Tsirkin
2019-09-08 11:53       ` [Virtio-fs] " piaojun
2019-09-09 16:14         ` Stefan Hajnoczi
2019-09-09 16:18           ` Michael S. Tsirkin
2019-09-09 23:52           ` piaojun
2019-09-06 13:37 ` Michael S. Tsirkin

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