Re: [PATCH V8 17/19] virtio_ring: factor out split indirect detaching logic

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

On Mon, Oct 20, 2025 at 03:10:01PM +0800, Jason Wang wrote:
> Factor out the split indirect descriptor detaching logic in order to
> allow it to 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(-)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index c59e27e2ad68..0f07a6637acb 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;

so extra is initialized here ....

> +	struct vring_desc *indir_desc =
> +	       vq->split.desc_state[head].indir_desc;
> +	unsigned int j;
> +	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];


only to be over-written here.

what's up with this?

> +
> +	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;
> +}
> +