linux-kernel - Re: [PATCH v3 7/7] virtio_balloon: Stop calling page_address() in free

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Message-ID: <20250904173824-mutt-send-email-mst@kernel.org>
Date: Thu, 4 Sep 2025 17:38:30 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-block@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
	linux-efi@...r.kernel.org, virtualization@...ts.linux.dev,
	David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH v3 7/7] virtio_balloon: Stop calling page_address() in
 free_pages()

On Wed, Sep 03, 2025 at 11:59:21AM -0700, Vishal Moola (Oracle) wrote:
> free_pages() should be used when we only have a virtual address. We
> should call __free_pages() directly on our page instead.
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
>  drivers/virtio/virtio_balloon.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index eae65136cdfb..7f3fd72678eb 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -488,8 +488,7 @@ static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
>  		page = balloon_page_pop(&vb->free_page_list);
>  		if (!page)
>  			break;
> -		free_pages((unsigned long)page_address(page),
> -			   VIRTIO_BALLOON_HINT_BLOCK_ORDER);
> +		__free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
>  	}
>  	vb->num_free_page_blocks -= num_returned;
>  	spin_unlock_irq(&vb->free_page_list_lock);
> @@ -719,8 +718,7 @@ static int get_free_page_and_send(struct virtio_balloon *vb)
>  	if (vq->num_free > 1) {
>  		err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
>  		if (unlikely(err)) {
> -			free_pages((unsigned long)p,
> -				   VIRTIO_BALLOON_HINT_BLOCK_ORDER);
> +			__free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
>  			return err;
>  		}
>  		virtqueue_kick(vq);
> @@ -733,7 +731,7 @@ static int get_free_page_and_send(struct virtio_balloon *vb)
>  		 * The vq has no available entry to add this page block, so
>  		 * just free it.
>  		 */
> -		free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
> +		__free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
>  	}
>  
>  	return 0;
> -- 
> 2.51.0