[PATCH 15/18] virtiofs: Make virtio_fs object refcounted

Stefan Hajnoczi
2019-09-06T12:03:09Z

On Thu, Sep 05, 2019 at 03:48:56PM -0400, 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 at redhat.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 virtiofs_put(struct virtio_fs *fs)

Why do the two function names above contain "virtiofs" instead
of "virtio_fs"?  I'm not sure if this is intentional and is
supposed to
mean something, but it's confusing.

> +{
> +	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)

Minor issue: this function name is confusingly similar to
virtiofs_put().  Please rename to virtio_fs_fiq_put().
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