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[67.164.59.41]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2468f5de849sm112338435ad.141.2025.08.27.11.29.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Aug 2025 11:29:24 -0700 (PDT) Date: Wed, 27 Aug 2025 11:29:22 -0700 From: "Vishal Moola (Oracle)" To: David Hildenbrand Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , "Michael S. Tsirkin" Subject: Re: [PATCH v2 7/7] virtio_balloon: Stop calling page_address() in free_pages() Message-ID: References: <20250826205617.1032945-1-vishal.moola@gmail.com> <20250826205617.1032945-8-vishal.moola@gmail.com> <5ee2b684-94d9-40be-b01c-b0538ced33bc@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="vepaSp8giM4exkxF" Content-Disposition: inline In-Reply-To: <5ee2b684-94d9-40be-b01c-b0538ced33bc@redhat.com> --vepaSp8giM4exkxF Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Aug 27, 2025 at 02:01:01PM +0200, David Hildenbrand wrote: > On 26.08.25 22:56, 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) > > --- > > drivers/virtio/virtio_balloon.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > > index eae65136cdfb..d4e6865ce355 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); > > I think you missed another nastiness of similar kind in > get_free_page_and_send() where we do > > p = page_address(page); > > Just to call > > free_pages((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER); Thanks for catching that. Andrew can you fold the attached patch into this one please? It looks like the page_address() call is needed for other things, but since we're changing the file we might as well clean these up as well. I imagine theres more of these lingering in the kernel, but theres so many callers and I only looked for the ones that were calling page_address() inline :(. --vepaSp8giM4exkxF Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename=0001-virtio_ballon-Call-__free_pages-in-get_free_page_and.patch >From a7d439154c7990418da976e5864b91fce9d49d58 Mon Sep 17 00:00:00 2001 From: "Vishal Moola (Oracle)" Date: Wed, 27 Aug 2025 11:10:22 -0700 Subject: [PATCH] virtio_ballon: Call __free_pages() in get_free_page_and_send() 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) --- drivers/virtio/virtio_balloon.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index d4e6865ce355..7f3fd72678eb 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -718,8 +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); @@ -732,7 +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 --vepaSp8giM4exkxF--