linux-kernel - Re: [Virtio-fs] [PATCH 15/18] virtiofs: Make virtio

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Date:   Mon, 9 Sep 2019 11:35:37 -0400
From:   Vivek Goyal <vgoyal@...hat.com>
To:     piaojun <piaojun@...wei.com>
Cc:     linux-fsdevel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, miklos@...redi.hu,
        mst@...hat.com, linux-kernel@...r.kernel.org, virtio-fs@...hat.com
Subject: Re: [Virtio-fs] [PATCH 15/18] virtiofs: Make virtio_fs object
 refcounted

On Sun, Sep 08, 2019 at 07:10:03PM +0800, piaojun wrote:
> 
> 
> On 2019/9/6 3:48, Vivek Goyal wrote:
> > This object is used both by fuse_connection as well virt device. So make
> > this object reference counted and that makes it easy to define life cycle
> > of the object.
> > 
> > Now deivce can be removed while filesystem is still mounted. This will
> > cleanup all the virtqueues but virtio_fs object will still be around and
> > will be cleaned when filesystem is unmounted and sb/fc drops its reference.
> > 
> > Removing a device also stops all virt queues and any new reuqest gets
> > error -ENOTCONN. All existing in flight requests are drained before
> > ->remove returns.
> > 
> > Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
> > ---
> >  fs/fuse/virtio_fs.c | 52 +++++++++++++++++++++++++++++++++++++--------
> >  1 file changed, 43 insertions(+), 9 deletions(-)
> > 
> > diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> > index 01bbf2c0e144..29ec2f5bbbe2 100644
> > --- a/fs/fuse/virtio_fs.c
> > +++ b/fs/fuse/virtio_fs.c
> > @@ -37,6 +37,7 @@ struct virtio_fs_vq {
> >  
> >  /* A virtio-fs device instance */
> >  struct virtio_fs {
> > +	struct kref refcount;
> >  	struct list_head list;    /* on virtio_fs_instances */
> >  	char *tag;
> >  	struct virtio_fs_vq *vqs;
> > @@ -63,6 +64,27 @@ static inline struct fuse_pqueue *vq_to_fpq(struct virtqueue *vq)
> >  	return &vq_to_fsvq(vq)->fud->pq;
> >  }
> >  
> > +static void release_virtiofs_obj(struct kref *ref)
> > +{
> > +	struct virtio_fs *vfs = container_of(ref, struct virtio_fs, refcount);
> > +
> > +	kfree(vfs->vqs);
> > +	kfree(vfs);
> > +}
> > +
> > +static void virtio_fs_put(struct virtio_fs *fs)
> > +{
> > +	mutex_lock(&virtio_fs_mutex);
> > +	kref_put(&fs->refcount, release_virtiofs_obj);
> > +	mutex_unlock(&virtio_fs_mutex);
> > +}
> > +
> > +static void virtio_fs_put(struct fuse_iqueue *fiq)
> > +{
> > +	struct virtio_fs *vfs = fiq->priv;
> > +	virtiofs_put(vfs);
> > +}
> 
> It's a little confusing that virtiofs_put() looks like virtiofs_put(),
> and could we use __virtio_fs_put to replace virtio_fs_put?

Fixed this in follow up patch I posted.

https://www.redhat.com/archives/virtio-fs/2019-September/msg00091.html

Vivek