In this commit:

commit fedc37448fb1be5d03e420ca7791d4286893d5ec
Author: SeongJae Park <sjpark@amazon.de>
Date:   Tue Aug 10 16:55:51 2021 +1000

    mm/idle_page_tracking: make PG_idle reusable

diff --git a/mm/Kconfig b/mm/Kconfig
index 504336de9a1e..d0b85dc12429 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -739,10 +739,18 @@ config DEFERRED_STRUCT_PAGE_INIT
          lifetime of the system until these kthreads finish the
          initialisation.

+config PAGE_IDLE_FLAG
+       bool "Add PG_idle and PG_young flags"
+       help
+         This feature adds PG_idle and PG_young flags in 'struct page'.  PTE
+         Accessed bit writers can set the state of the bit in the flags to let
+         other PTE Accessed bit readers don't disturbed.

This needs to be converted to proper, or at least comprehensible, English....