[PATCH v2] mm: rename CONFIG_PAGE_BLOCK_ORDER to CONFIG_PAGE_BLOCK_MAX_ORDER.

[Zi Yan <ziy@nvidia.com>]

The config is in fact an additional upper limit of pageblock_order, so
rename it to avoid confusion.

Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Juan Yescas <jyescas@google.com>
---
From v1[1]:
1. used a new name: PAGE_BLOCK_MAX_ORDER,
2. added the missing PAGE_BLOCK_ORDER rename in mm/mm_init.c[2]
3. dropped the Fixes tag.

[1] https://lore.kernel.org/linux-mm/20250603154843.1565239-1-ziy@nvidia.com/
[2] https://lore.kernel.org/linux-mm/202506042058.XgvABCE0-lkp@intel.com/

 include/linux/mmzone.h          | 14 +++++++-------
 include/linux/pageblock-flags.h |  8 ++++----
 mm/Kconfig                      | 15 ++++++++-------
 mm/mm_init.c                    |  2 +-
 4 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 283913d42d7b..5bec8b1d0e66 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -38,19 +38,19 @@
 #define NR_PAGE_ORDERS (MAX_PAGE_ORDER + 1)
 
 /* Defines the order for the number of pages that have a migrate type. */
-#ifndef CONFIG_PAGE_BLOCK_ORDER
-#define PAGE_BLOCK_ORDER MAX_PAGE_ORDER
+#ifndef CONFIG_PAGE_BLOCK_MAX_ORDER
+#define PAGE_BLOCK_MAX_ORDER MAX_PAGE_ORDER
 #else
-#define PAGE_BLOCK_ORDER CONFIG_PAGE_BLOCK_ORDER
-#endif /* CONFIG_PAGE_BLOCK_ORDER */
+#define PAGE_BLOCK_MAX_ORDER CONFIG_PAGE_BLOCK_MAX_ORDER
+#endif /* CONFIG_PAGE_BLOCK_MAX_ORDER */
 
 /*
  * The MAX_PAGE_ORDER, which defines the max order of pages to be allocated
- * by the buddy allocator, has to be larger or equal to the PAGE_BLOCK_ORDER,
+ * by the buddy allocator, has to be larger or equal to the PAGE_BLOCK_MAX_ORDER,
  * which defines the order for the number of pages that can have a migrate type
  */
-#if (PAGE_BLOCK_ORDER > MAX_PAGE_ORDER)
-#error MAX_PAGE_ORDER must be >= PAGE_BLOCK_ORDER
+#if (PAGE_BLOCK_MAX_ORDER > MAX_PAGE_ORDER)
+#error MAX_PAGE_ORDER must be >= PAGE_BLOCK_MAX_ORDER
 #endif
 
 /*
diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index e73a4292ef02..6297c6343c55 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -41,18 +41,18 @@ extern unsigned int pageblock_order;
  * Huge pages are a constant size, but don't exceed the maximum allocation
  * granularity.
  */
-#define pageblock_order		MIN_T(unsigned int, HUGETLB_PAGE_ORDER, PAGE_BLOCK_ORDER)
+#define pageblock_order		MIN_T(unsigned int, HUGETLB_PAGE_ORDER, PAGE_BLOCK_MAX_ORDER)
 
 #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
 
 #elif defined(CONFIG_TRANSPARENT_HUGEPAGE)
 
-#define pageblock_order		MIN_T(unsigned int, HPAGE_PMD_ORDER, PAGE_BLOCK_ORDER)
+#define pageblock_order		MIN_T(unsigned int, HPAGE_PMD_ORDER, PAGE_BLOCK_MAX_ORDER)
 
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 
-/* If huge pages are not used, group by PAGE_BLOCK_ORDER */
-#define pageblock_order		PAGE_BLOCK_ORDER
+/* If huge pages are not used, group by PAGE_BLOCK_MAX_ORDER */
+#define pageblock_order		PAGE_BLOCK_MAX_ORDER
 
 #endif /* CONFIG_HUGETLB_PAGE */
 
diff --git a/mm/Kconfig b/mm/Kconfig
index 65089552e124..3afac26d3594 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1017,8 +1017,8 @@ config ARCH_FORCE_MAX_ORDER
 # the default page block order is MAX_PAGE_ORDER (10) as per
 # include/linux/mmzone.h.
 #
-config PAGE_BLOCK_ORDER
-	int "Page Block Order"
+config PAGE_BLOCK_MAX_ORDER
+	int "Page Block Order Upper Limit"
 	range 1 10 if ARCH_FORCE_MAX_ORDER = 0
 	default 10 if ARCH_FORCE_MAX_ORDER = 0
 	range 1 ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER != 0
@@ -1026,12 +1026,13 @@ config PAGE_BLOCK_ORDER
 	help
 	  The page block order refers to the power of two number of pages that
 	  are physically contiguous and can have a migrate type associated to
-	  them. The maximum size of the page block order is limited by
-	  ARCH_FORCE_MAX_ORDER.
+	  them. The maximum size of the page block order is at least limited by
+	  ARCH_FORCE_MAX_ORDER/MAX_PAGE_ORDER.
 
-	  This config allows overriding the default page block order when the
-	  page block order is required to be smaller than ARCH_FORCE_MAX_ORDER
-	  or MAX_PAGE_ORDER.
+	  This config adds a new upper limit of default page block
+	  order when the page block order is required to be smaller than
+	  ARCH_FORCE_MAX_ORDER/MAX_PAGE_ORDER or other limits
+	  (see include/linux/pageblock-flags.h for details).
 
 	  Reducing pageblock order can negatively impact THP generation
 	  success rate. If your workloads use THP heavily, please use this
diff --git a/mm/mm_init.c b/mm/mm_init.c
index f2944748f526..02f41e2bdf60 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1509,7 +1509,7 @@ static inline void setup_usemap(struct zone *zone) {}
 /* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
 void __init set_pageblock_order(void)
 {
-	unsigned int order = PAGE_BLOCK_ORDER;
+	unsigned int order = PAGE_BLOCK_MAX_ORDER;
 
 	/* Check that pageblock_nr_pages has not already been setup */
 	if (pageblock_order)
-- 
2.47.2