Re: [PATCH v1 4/4] page_reporting: change PAGE_REPORTING_DEFAULT_ORDER to -1

["David Hildenbrand (Arm)" <david@kernel.org>]

On 2/27/26 15:06, Yuvraj Sakshith wrote:
> PAGE_REPORTING_DEFAULT_ORDER is now set to zero. This means,
> pages of order zero cannot be reported to a client/driver -- as zero
> is used to signal a fallback to MAX_PAGE_ORDER.
> 
> Change PAGE_REPORTING_DEFAULT_ORDER to (-1),
> so that zero can be used as a valid order with which pages can
> be reported.
> 
> Signed-off-by: Yuvraj Sakshith <yuvraj.sakshith@oss.qualcomm.com>
> ---
>  include/linux/page_reporting.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h
> index a7e3e30f2..3eb3e26d8 100644
> --- a/include/linux/page_reporting.h
> +++ b/include/linux/page_reporting.h
> @@ -7,7 +7,7 @@
>  
>  /* This value should always be a power of 2, see page_reporting_cycle() */
>  #define PAGE_REPORTING_CAPACITY		32
> -#define PAGE_REPORTING_DEFAULT_ORDER	0
> +#define PAGE_REPORTING_DEFAULT_ORDER	(-1)

No need for the ().

Wondering whether we now also want to do in this patch:


diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index f0042d5743af..d432aadf9d07 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -11,8 +11,7 @@
 #include "page_reporting.h"
 #include "internal.h"

-/* Initialize to an unsupported value */
-unsigned int page_reporting_order = -1;
+unsigned int page_reporting_order = PAGE_REPORTING_DEFAULT_ORDER;

 static int page_order_update_notify(const char *val, const struct
kernel_param *kp)
 {
@@ -369,7 +368,7 @@ int page_reporting_register(struct
page_reporting_dev_info *prdev)
         * pageblock_order.
         */

-       if (page_reporting_order == -1) {
+       if (page_reporting_order == PAGE_REPORTING_DEFAULT_ORDER) {



(and wondering whether we should have called it
PAGE_REPORTING_USE_DEFAULT_ORDER to make it clearer that it is not an
actual order. Leaving that up to you :) )

-- 
Cheers,

David