[Devel] [PATCH RH9 08/10] drivers/vhost: add API to queue work at virtqueue worker

[Konstantin Khorenko]

On 16.08.2022 09:44, Andrey Zhadchenko wrote:
> Add routines to queue works on virtqueue assigned workers
> 
> https://jira.sw.ru/browse/PSBM-139414
> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
> ---
>   drivers/vhost/vhost.c | 22 ++++++++++++++++++++++
>   drivers/vhost/vhost.h |  5 +++++
>   2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 965299b0c0a3..5cf3d8eccfff 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -274,6 +274,17 @@ static void vhost_worker_flush(struct vhost_worker *w)
>   	wait_for_completion(&flush.wait_event);
>   }
>   
> +void vhost_work_flush_vq(struct vhost_virtqueue *vq)
> +{
> +	struct vhost_worker *w = READ_ONCE(vq->worker);
> +
> +	if (!w)
> +		return;
> +
> +	vhost_worker_flush(w);
> +}
> +EXPORT_SYMBOL_GPL(vhost_work_flush_vq);
> +
>   /* Flush any work that has been scheduled. When calling this, don't hold any
>    * locks that are also used by the callback. */
>   void vhost_poll_flush(struct vhost_poll *poll)
> @@ -293,6 +304,17 @@ void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
>   }
>   EXPORT_SYMBOL_GPL(vhost_work_queue);
>   
> +void vhost_work_queue_vq(struct vhost_virtqueue *vq, struct vhost_work *work)
> +{
> +	struct vhost_worker *w = READ_ONCE(vq->worker);
> +
> +	if (!w)
> +		return;

Why if we try to queue a work and fail because of no worker - there is nothing to worry about?

> +
> +	vhost_work_queue_at_worker(w, work);
> +}
> +EXPORT_SYMBOL_GPL(vhost_work_queue_vq);
> +
>   /* A lockless hint for busy polling code to exit the loop */
>   bool vhost_has_work(struct vhost_dev *dev)
>   {
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 9632f6501617..dc7428c26cbe 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -142,6 +142,11 @@ struct vhost_virtqueue {
>   	struct vhost_worker *worker;
>   };
>   
> +/* Queue the work on virtqueue assigned worker */
> +void vhost_work_queue_vq(struct vhost_virtqueue *vq, struct vhost_work *work);
> +/* Flush virtqueue assigned worker */
> +void vhost_work_flush_vq(struct vhost_virtqueue *vq);
> +
>   struct vhost_msg_node {
>     union {
>   	  struct vhost_msg msg;