Date: Tue, 3 Sep 2019 13:15:16 -0400
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20190903111628-mutt-send-email-mst@kernel.org>
References: <20190821173742.24574-1-vgoyal@redhat.com>
	<CAJfpegvPTxkaNhXWhiQSprSJqyW1cLXeZEz6x_f0PxCd-yzHQg@mail.gmail.com>
	<20190903041507-mutt-send-email-mst@kernel.org>
	<20190903140752.GA10983@redhat.com>
	<20190903101001-mutt-send-email-mst@kernel.org>
	<20190903141851.GC10983@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190903141851.GC10983@redhat.com>
Subject: Re: [Virtio-fs] [PATCH v3 00/13] virtio-fs: shared file system for
 virtual machines
List-Id: Development discussions about virtio-fs <virtio-fs.redhat.com>
List-Unsubscribe: <https://www.redhat.com/mailman/options/virtio-fs>,
	<mailto:virtio-fs-request@redhat.com?subject=unsubscribe>
List-Archive: <https://www.redhat.com/archives/virtio-fs>
List-Post: <mailto:virtio-fs@redhat.com>
List-Help: <mailto:virtio-fs-request@redhat.com?subject=help>
List-Subscribe: <https://www.redhat.com/mailman/listinfo/virtio-fs>,
	<mailto:virtio-fs-request@redhat.com?subject=subscribe>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>, Jason Wang <jasowang@redhat.com>, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, virtio-fs@redhat.com, linux-fsdevel@vger.kernel.org

On Tue, Sep 03, 2019 at 10:18:51AM -0400, Vivek Goyal wrote:
> On Tue, Sep 03, 2019 at 10:12:16AM -0400, Michael S. Tsirkin wrote:
> > On Tue, Sep 03, 2019 at 10:07:52AM -0400, Vivek Goyal wrote:
> > > On Tue, Sep 03, 2019 at 04:31:38AM -0400, Michael S. Tsirkin wrote:
> > > 
> > > [..]
> > > > +	/* TODO lock */
> > > > give me pause.
> > > > 
> > > > Cleanup generally seems broken to me - what pauses the FS
> > > 
> > > I am looking into device removal aspect of it now. Thinking of adding
> > > a reference count to virtiofs device and possibly also a bit flag to
> > > indicate if device is still alive. That way, we should be able to cleanup
> > > device more gracefully.
> > 
> > Generally, the way to cleanup things is to first disconnect device from
> > linux so linux won't send new requests, wait for old ones to finish.
> 
> I was thinking of following.
> 
> - Set a flag on device to indicate device is dead and not queue new
>   requests. Device removal call can set this flag.
> 
> - Return errors when fs code tries to queue new request.
> 
> - Drop device creation reference in device removal path. If device is
>   mounted at the time of removal, that reference will still be active
>   and device state will not be cleaned up in kernel yet.
> 
> - User unmounts the fs, and that will drop last reference to device and
>   will lead to cleanup of in kernel state of the device.
> 
> Does that sound reasonable.
> 
> Vivek

Just we aware of the fact that virtio device, all vqs etc
will be gone by the time remove returns.


-- 
MST