Re: [PATCH v2 11/23] drivers/virtio/virtio_balloon: stop using balloon_page_push/pop()

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Thu, Jan 15, 2026 at 10:20:01AM +0100, David Hildenbrand (Red Hat) wrote:
> Let's stop using these functions so we can remove them. They look like
> belonging to the balloon API for managing the device balloon list when
> really they are just simple helpers only used by virtio-balloon.
>
> Let's just inline them and switch to a proper
> list_for_each_entry_safe().
>
> Signed-off-by: David Hildenbrand (Red Hat) <david@kernel.org>

Overall LGTM, some small enquiry really below. So:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

> ---
>  drivers/virtio/virtio_balloon.c | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 15c1cf5fd249c..6ae00de78b61b 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -242,8 +242,8 @@ static void set_page_pfns(struct virtio_balloon *vb,
>  static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
>  {
>  	unsigned int num_allocated_pages;
> +	struct page *page, *next;
>  	unsigned int num_pfns;
> -	struct page *page;
>  	LIST_HEAD(pages);
>
>  	/* We can only do one array worth at a time. */
> @@ -262,14 +262,15 @@ static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
>  			break;
>  		}
>
> -		balloon_page_push(&pages, page);

Seems this function is unused now, wonder if you remove in a subsequent patch?
If not should remove :)

Just had a look at it and what a silly function, guess was used for kinda
'self-documenting' that it was a balloon page insertion.

> +		list_add(&page->lru, &pages);
>  	}
>
>  	mutex_lock(&vb->balloon_lock);
>
>  	vb->num_pfns = 0;
>
> -	while ((page = balloon_page_pop(&pages))) {
> +	list_for_each_entry_safe(page, next, &pages, lru) {
> +		list_del(&page->lru);
>  		balloon_page_enqueue(&vb->vb_dev_info, page);
>
>  		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
> @@ -474,15 +475,19 @@ static inline s64 towards_target(struct virtio_balloon *vb)
>  static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
>  					     unsigned long num_to_return)
>  {
> -	struct page *page;
> -	unsigned long num_returned;
> +	unsigned long num_returned = 0;
> +	struct page *page, *next;
> +
> +	if (unlikely(!num_to_return))
> +		return 0;
>
>  	spin_lock_irq(&vb->free_page_list_lock);
> -	for (num_returned = 0; num_returned < num_to_return; num_returned++) {
> -		page = balloon_page_pop(&vb->free_page_list);
> -		if (!page)
> -			break;
> +
> +	list_for_each_entry_safe(page, next, &vb->free_page_list, lru) {
> +		list_del(&page->lru);
>  		__free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
> +		if (++num_returned == num_to_return)
> +			break;
>  	}
>  	vb->num_free_page_blocks -= num_returned;
>  	spin_unlock_irq(&vb->free_page_list_lock);
> @@ -717,7 +722,7 @@ static int get_free_page_and_send(struct virtio_balloon *vb)
>  		}
>  		virtqueue_kick(vq);
>  		spin_lock_irq(&vb->free_page_list_lock);
> -		balloon_page_push(&vb->free_page_list, page);
> +		list_add(&page->lru, &vb->free_page_list);
>  		vb->num_free_page_blocks++;
>  		spin_unlock_irq(&vb->free_page_list_lock);
>  	} else {
> --
> 2.52.0
>