On 2/26/26 08:01, Yuvraj Sakshith wrote:
> Drivers registering with page reporting used zero
> as a way to signal page_reporting_order to be set
> as a default value (either passed as a param or
> MAX_PAGE_ORDER).
>
> Since page_reporting_order can now have zero as
> valid order, default fallback value send by drivers
> to page reporting is now -1.
>
> Signed-off-by: Yuvraj Sakshith <[email protected]>
> ---
> drivers/virtio/virtio_balloon.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 74fe59f5a..3cc3dc28a 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -1044,6 +1044,20 @@ static int virtballoon_probe(struct virtio_device
> *vdev)
> goto out_unregister_oom;
> }
>
> + /*
> + * page_reporting_register() takes the order either
> + * from the driver or the commandline. If neither
> + * are provided, it falls back to MAX_PAGE_ORDER.
> + *
> + * Order given by the driver is required to be in the
> + * range [0, MAX_PAGE_ORDER].
> + *
> + * One way for the driver to not provide any order
> + * is by setting it to -1.
> + */
> +
> + vb->pr_dev_info.order = -1;
That overly-long comment indicates that we can do better.
What about the following:
Patch #1: Introduce PAGE_REPORTING_DEFAULT_ORDER
diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h
index fe648dfa3a7c..3e21bfbb49a4 100644
--- a/include/linux/page_reporting.h
+++ b/include/linux/page_reporting.h
@@ -8,6 +8,9 @@
/* This value should always be a power of 2, see page_reporting_cycle() */
#define PAGE_REPORTING_CAPACITY 32
+/* Specifying this value as minimal reporting order selects the default. */
+#define PAGE_REPORTING_DEFAULT_ORDER 0
+
struct page_reporting_dev_info {
/* function that alters pages to make them "reported" */
int (*report)(struct page_reporting_dev_info *prdev,
diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index f0042d5743af..d5191cb6b31c 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -370,7 +370,8 @@ int page_reporting_register(struct page_reporting_dev_info
*prdev)
*/
if (page_reporting_order == -1) {
- if (prdev->order > 0 && prdev->order <= MAX_PAGE_ORDER)
+ if (prdev->order != PAGE_REPORTING_DEFAULT_ORDER &&
+ prdev->order <= MAX_PAGE_ORDER)
page_reporting_order = prdev->order;
else
page_reporting_order = pageblock_order;
Patch #2: Use the define in hyperv
Patch #3: Use the define in virtio-balloon
Patch #4: Change PAGE_REPORTING_DEFAULT_ORDER to "MAX_PAGE_ORDER + 1" or sth.
like that.
Then I think you can just drop the comment in virtballoon_probe() completely.
--
Cheers,
David
