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From: Vivek Goyal <vgoyal@redhat.com>
To: Miklos Szeredi <miklos@szeredi.hu>
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 08:08:17 -0400	[thread overview]
Message-ID: <20190906120817.GA22083@redhat.com> (raw)
In-Reply-To: <CAJfpegudNVZitQ5L8gPvA45mRPFDk9fhyboceVW6xShpJ4mLww@mail.gmail.com>

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.

Thanks
Vivek

  reply	other threads:[~2019-09-06 12:08 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 [this message]
2019-09-06 13:55         ` Miklos Szeredi
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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