linux-kernel - Re: [PATCH V6 15/19] virtio_ring: factor out core logic of buffer detaching

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Message-ID: <20250921134159-mutt-send-email-mst@kernel.org>
Date: Sun, 21 Sep 2025 13:42:47 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: xuanzhuo@...ux.alibaba.com, eperezma@...hat.com,
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 15/19] virtio_ring: factor out core logic of buffer
 detaching

On Fri, Sep 19, 2025 at 03:31:50PM +0800, Jason Wang wrote:
> Factor out core logic of buffer detaching and leave the id population
> to the caller so in order can just call the core logic.
> 
> Acked-by: Eugenio Pérez <eperezma@...hat.com>
> Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/virtio/virtio_ring.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 0949675a3d12..a83d08070e8a 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1662,8 +1662,8 @@ static bool virtqueue_kick_prepare_packed(struct vring_virtqueue *vq)
>  	return needs_kick;
>  }
>  
> -static void detach_buf_packed(struct vring_virtqueue *vq,
> -			      unsigned int id, void **ctx)
> +static void detach_buf_packed_in_order(struct vring_virtqueue *vq,
> +				       unsigned int id, void **ctx)
>  {
>  	struct vring_desc_state_packed *state = NULL;
>  	struct vring_packed_desc *desc;
> @@ -1674,8 +1674,6 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
>  	/* Clear data ptr. */
>  	state->data = NULL;
>  
> -	vq->packed.desc_extra[state->last].next = vq->free_head;
> -	vq->free_head = id;
>  	vq->vq.num_free += state->num;
>  
>  	if (unlikely(vq->use_map_api)) {
> @@ -1712,6 +1710,17 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
>  	}
>  }
>  
> +static void detach_buf_packed(struct vring_virtqueue *vq,
> +			      unsigned int id, void **ctx)
> +{
> +	struct vring_desc_state_packed *state = &vq->packed.desc_state[id];
> +
> +	vq->packed.desc_extra[state->last].next = vq->free_head;
> +	vq->free_head = id;
> +
> +	return detach_buf_packed_in_order(vq, id, ctx);
> +}
> +

Wait what? return in a void function?
How does this compile? I'm guessing it's tweaked by a follow
up patch?


>  static inline bool is_used_desc_packed(const struct vring_virtqueue *vq,
>  				       u16 idx, bool used_wrap_counter)
>  {
> -- 
> 2.31.1