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

Lorenzo Stoakes
2026-01-15T12:29:04Z

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
>