Re: [PATCH V6 17/19] virtio_ring: factor out split indirect detaching logic

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Sep 19, 2025 at 03:31:52PM +0800, Jason Wang wrote:
> Factor out the split indirect descriptor detaching logic in order to
> make it be reused by the in order support.
> 
> Acked-by: Eugenio Pérez <eperezma@redhat.com>
> Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++----------------
>  1 file changed, 35 insertions(+), 28 deletions(-)


it is just a refactoring but the code can be prettified a bit. see
below. you can make it a separate patch if you prefer but i think
it is ok to do here.

> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index f376f717c8e4..5aa0cd785362 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -771,11 +771,42 @@ static bool virtqueue_kick_prepare_split(struct vring_virtqueue *vq)
>  	return needs_kick;
>  }
>  
> +static void detach_indirect_split(struct vring_virtqueue *vq,
> +				  unsigned int head)
> +{
> +	struct vring_desc_extra *extra = vq->split.desc_extra;
> +	struct vring_desc *indir_desc =
> +	       vq->split.desc_state[head].indir_desc;

We no longer need to split this.
It was like this because it was indented.
By itself  it fits under 80 chars even without and
that is no longer a hard limit.

> +	unsigned int j;
> +	u32 len, num;
> +
> +	/* Free the indirect table, if any, now that it's unmapped. */
> +	if (!indir_desc)
> +		return;


en empty line won't hurt here.

> +	len = vq->split.desc_extra[head].len;
> +
> +	BUG_ON(!(vq->split.desc_extra[head].flags &
> +			VRING_DESC_F_INDIRECT));

same thing here. no need to wrap anymore.


> +	BUG_ON(len == 0 || len % sizeof(struct vring_desc));
> +
> +	num = len / sizeof(struct vring_desc);
> +
> +	extra = (struct vring_desc_extra *)&indir_desc[num];
> +
> +	if (vq->use_map_api) {
> +		for (j = 0; j < num; j++)
> +			vring_unmap_one_split(vq, &extra[j]);
> +	}

use of {} questionable. we can keep it if you prefer though.

> +
> +	kfree(indir_desc);
> +	vq->split.desc_state[head].indir_desc = NULL;
> +}
> +
>  static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
>  			     void **ctx)
>  {
>  	struct vring_desc_extra *extra;
> -	unsigned int i, j;
> +	unsigned int i;
>  	__virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
>  
>  	/* Clear data ptr. */
> @@ -799,34 +830,10 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
>  	/* Plus final descriptor */
>  	vq->vq.num_free++;
>  
> -	if (vq->indirect) {
> -		struct vring_desc *indir_desc =
> -				vq->split.desc_state[head].indir_desc;
> -		u32 len, num;
> -
> -		/* Free the indirect table, if any, now that it's unmapped. */
> -		if (!indir_desc)
> -			return;
> -		len = vq->split.desc_extra[head].len;
> -
> -		BUG_ON(!(vq->split.desc_extra[head].flags &
> -				VRING_DESC_F_INDIRECT));
> -		BUG_ON(len == 0 || len % sizeof(struct vring_desc));
> -
> -		num = len / sizeof(struct vring_desc);
> -
> -		extra = (struct vring_desc_extra *)&indir_desc[num];
> -
> -		if (vq->use_map_api) {
> -			for (j = 0; j < num; j++)
> -				vring_unmap_one_split(vq, &extra[j]);
> -		}
> -
> -		kfree(indir_desc);
> -		vq->split.desc_state[head].indir_desc = NULL;
> -	} else if (ctx) {
> +	if (vq->indirect)
> +		detach_indirect_split(vq, head);
> +	else if (ctx)
>  		*ctx = vq->split.desc_state[head].indir_desc;
> -	}
>  }
>  
>  static bool virtqueue_poll_split(const struct vring_virtqueue *vq,
> -- 
> 2.31.1