Re: [PATCH v2 1/4] mm/page_reporting: add PAGE_REPORTING_ORDER_UNSPECIFIED

[David Hildenbrand (Arm)]

On 3/2/26 12:17, Yuvraj Sakshith wrote:
> Drivers can pass order of pages to be reported while
> registering itself. Today, this is a magic number, 0.
> 
> Label this with PAGE_REPORTING_ORDER_UNSPECIFIED and
> check for it when the driver is being registered.
> 
> This macro will be used in relevant drivers next.
> 
> Signed-off-by: Yuvraj Sakshith <yuvraj.sakshith@xxxxxxxxxxxxxxxx>
> ---
>  include/linux/page_reporting.h |  1 +
>  mm/page_reporting.c            | 14 +++++---------
>  2 files changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h
> index fe648dfa3..d1886c657 100644
> --- a/include/linux/page_reporting.h
> +++ b/include/linux/page_reporting.h
> @@ -7,6 +7,7 @@
>  
>  /* This value should always be a power of 2, see page_reporting_cycle() */
>  #define PAGE_REPORTING_CAPACITY		32
> +#define PAGE_REPORTING_ORDER_UNSPECIFIED	0
>  
>  struct page_reporting_dev_info {
>  	/* function that alters pages to make them "reported" */
> diff --git a/mm/page_reporting.c b/mm/page_reporting.c
> index e4c428e61..51cd88faf 100644
> --- a/mm/page_reporting.c
> +++ b/mm/page_reporting.c
> @@ -12,7 +12,7 @@
>  #include "internal.h"
>  
>  /* Initialize to an unsupported value */
> -unsigned int page_reporting_order = -1;
> +unsigned int page_reporting_order = PAGE_REPORTING_ORDER_UNSPECIFIED;
>  
>  static int page_order_update_notify(const char *val, const struct kernel_param *kp)
>  {
> @@ -25,12 +25,7 @@ static int page_order_update_notify(const char *val, const struct kernel_param *
>  
>  static const struct kernel_param_ops page_reporting_param_ops = {
>  	.set = &page_order_update_notify,
> -	/*
> -	 * For the get op, use param_get_int instead of param_get_uint.
> -	 * This is to make sure that when unset the initialized value of
> -	 * -1 is shown correctly
> -	 */
> -	.get = &param_get_int,
> +	.get = &param_get_uint,
>  };
>  
>  module_param_cb(page_reporting_order, &page_reporting_param_ops,
> @@ -369,8 +364,9 @@ int page_reporting_register(struct page_reporting_dev_info *prdev)
>  	 * pageblock_order.
>  	 */
>  
> -	if (page_reporting_order == -1) {
> -		if (prdev->order > 0 && prdev->order <= MAX_PAGE_ORDER)
> +	if (page_reporting_order == PAGE_REPORTING_ORDER_UNSPECIFIED) {
> +		if (prdev->order != PAGE_REPORTING_ORDER_UNSPECIFIED &&
> +			prdev->order <= MAX_PAGE_ORDER)
>  			page_reporting_order = prdev->order;
>  		else
>  			page_reporting_order = pageblock_order;

I think the change to page_reporting_order (and param_get_int) should
come after patch #4.

Otherwise, you temporarily change the semantics of
page_reporting_param_ops() etc.

So you should perform the page_reporting_order changes either in patch
#4 or in a new patch #5.

Apart from that LGTM.

-- 
Cheers,

David