linux-kernel - Re: [PATCH v1 11/23] drivers/virtio/virtio_balloon: stop using balloon_page

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Message-ID: <20251021165854-mutt-send-email-mst@kernel.org>
Date: Tue, 21 Oct 2025 16:59:10 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...ts.ozlabs.org,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	linux-doc@...r.kernel.org, virtualization@...ts.linux.dev,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oscar Salvador <osalvador@...e.de>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>, Jonathan Corbet <corbet@....net>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jerrin Shaji George <jerrin.shaji-george@...adcom.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Zi Yan <ziy@...dia.com>
Subject: Re: [PATCH v1 11/23] drivers/virtio/virtio_balloon: stop using
 balloon_page_push/pop()

On Tue, Oct 21, 2025 at 02:59:16PM +0200, David Hildenbrand wrote:
> Let's stop using these function

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 <david@...hat.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 f7d6a4a6e54f5..4b22de6a5f845 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);
> +		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 {
> -- 
> 2.51.0