On 9 Aug 2021, at 10:12, Alexander Duyck wrote: > On Mon, Aug 9, 2021 at 12:25 AM David Hildenbrand wrote: >> >> On 05.08.21 21:02, Zi Yan wrote: >>> From: Zi Yan >>> >>> page_reporting_order was set to MAX_ORDER, which is always smaller than >>> a memory section size. An upcoming change will make MAX_ORDER larger >>> than a memory section size. Set page_reporting_order to >>> PFN_SECTION_SHIFT to match existing size assumption. >>> >>> Signed-off-by: Zi Yan >>> Cc: David Hildenbrand >>> Cc: linux-mm@kvack.org >>> Cc: linux-kernel@vger.kernel.org >>> --- >>> mm/page_reporting.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/mm/page_reporting.c b/mm/page_reporting.c >>> index 382958eef8a9..dc4a2d699862 100644 >>> --- a/mm/page_reporting.c >>> +++ b/mm/page_reporting.c >>> @@ -11,7 +11,8 @@ >>> #include "page_reporting.h" >>> #include "internal.h" >>> >>> -unsigned int page_reporting_order = MAX_ORDER; >>> +/* Set page_reporting_order at section size */ >>> +unsigned int page_reporting_order = PFN_SECTION_SHIFT; >>> module_param(page_reporting_order, uint, 0644); >>> MODULE_PARM_DESC(page_reporting_order, "Set page reporting order"); >>> >>> >> >> If you look closely, this is only a placeholder and will get overwritten >> in page_reporting_register(). I don't recall why we have the module >> parameter at all. Most probably, to adjust the reporting order after we >> already registered a user. Can't we just initialize that to 0 ? > > Yeah, it is pretty much there for debugging in the event that we are > on an architecture that is misconfigured. MAX_ORDER is changed to a boot time variable in Patch 15, thus cannot be used for page_reporting_order initialization after that. Thanks for David’s explanation. I will initialize page_reporting_order to 0 and fix the commit message. — Best Regards, Yan, Zi