mm, treewide: redefine MAX_ORDER sanely

MAX_ORDER currently defined as number of orders page allocator supports:
user can ask buddy allocator for page order between 0 and MAX_ORDER-1.

This definition is counter-intuitive and lead to number of bugs all over
the kernel.

Change the definition of MAX_ORDER to be inclusive: the range of orders
user can ask from buddy allocator is 0..MAX_ORDER now.

[kirill@shutemov.name: fix min() warning]
  Link: https://lkml.kernel.org/r/20230315153800.32wib3n5rickolvh@box
[akpm@linux-foundation.org: fix another min_t warning]
[kirill@shutemov.name: fixups per Zi Yan]
  Link: https://lkml.kernel.org/r/20230316232144.b7ic4cif4kjiabws@box.shutemov.name
[akpm@linux-foundation.org: fix underlining in docs]
  Link: https://lore.kernel.org/oe-kbuild-all/202303191025.VRCTk6mP-lkp@intel.com/
Link: https://lkml.kernel.org/r/20230315113133.11326-11-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>	[powerpc]
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

5 files changed, 12 insertions, 12 deletions

diff --git a/include/drm/ttm/ttm_pool.h b/include/drm/ttm/ttm_pool.h
index ef09b23d29e3..8ce14f9d202a 100644
--- a/include/drm/ttm/ttm_pool.h
+++ b/include/drm/ttm/ttm_pool.h
@@ -72,7 +72,7 @@ struct ttm_pool {
 	bool use_dma32;
 
 	struct {
-		struct ttm_pool_type orders[MAX_ORDER];
+		struct ttm_pool_type orders[MAX_ORDER + 1];
 	} caching[TTM_NUM_CACHING_TYPES];
 };
 
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 7c977d234aba..8fb7d91cd0b1 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -818,7 +818,7 @@ static inline unsigned huge_page_shift(struct hstate *h)
 
 static inline bool hstate_is_gigantic(struct hstate *h)
 {
-	return huge_page_order(h) >= MAX_ORDER;
+	return huge_page_order(h) > MAX_ORDER;
 }
 
 static inline unsigned int pages_per_huge_page(const struct hstate *h)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index bf8786d45b31..35b11cc210d9 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -26,11 +26,11 @@
 
 /* Free memory management - zoned buddy allocator.  */
 #ifndef CONFIG_ARCH_FORCE_MAX_ORDER
-#define MAX_ORDER 11
+#define MAX_ORDER 10
 #else
 #define MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
 #endif
-#define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1))
+#define MAX_ORDER_NR_PAGES (1 << MAX_ORDER)
 
 /*
  * PAGE_ALLOC_COSTLY_ORDER is the order at which allocations are deemed
@@ -93,7 +93,7 @@ static inline bool migratetype_is_mergeable(int mt)
 }
 
 #define for_each_migratetype_order(order, type) \
-	for (order = 0; order < MAX_ORDER; order++) \
+	for (order = 0; order <= MAX_ORDER; order++) \
 		for (type = 0; type < MIGRATE_TYPES; type++)
 
 extern int page_group_by_mobility_disabled;
@@ -922,7 +922,7 @@ struct zone {
 	CACHELINE_PADDING(_pad1_);
 
 	/* free areas of different sizes */
-	struct free_area	free_area[MAX_ORDER];
+	struct free_area	free_area[MAX_ORDER + 1];
 
 	/* zone flags, see below */
 	unsigned long		flags;
@@ -1745,7 +1745,7 @@ static inline bool movable_only_nodes(nodemask_t *nodes)
 #define SECTION_BLOCKFLAGS_BITS \
 	((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
 
-#if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
+#if (MAX_ORDER + PAGE_SHIFT) > SECTION_SIZE_BITS
 #error Allocator MAX_ORDER exceeds SECTION_SIZE
 #endif
 
diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index 5f1ae07d724b..e83c4c095041 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -41,14 +41,14 @@ 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, MAX_ORDER - 1)
+#define pageblock_order		min_t(unsigned int, HUGETLB_PAGE_ORDER, MAX_ORDER)
 
 #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
 
 #else /* CONFIG_HUGETLB_PAGE */
 
 /* If huge pages are not used, group by MAX_ORDER_NR_PAGES */
-#define pageblock_order		(MAX_ORDER-1)
+#define pageblock_order		MAX_ORDER
 
 #endif /* CONFIG_HUGETLB_PAGE */
 
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 45af70315a94..aa4575ef2965 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -284,7 +284,7 @@ static inline unsigned int arch_slab_minalign(void)
  * (PAGE_SIZE*2).  Larger requests are passed to the page allocator.
  */
 #define KMALLOC_SHIFT_HIGH	(PAGE_SHIFT + 1)
-#define KMALLOC_SHIFT_MAX	(MAX_ORDER + PAGE_SHIFT - 1)
+#define KMALLOC_SHIFT_MAX	(MAX_ORDER + PAGE_SHIFT)
 #ifndef KMALLOC_SHIFT_LOW
 #define KMALLOC_SHIFT_LOW	5
 #endif
@@ -292,7 +292,7 @@ static inline unsigned int arch_slab_minalign(void)
 
 #ifdef CONFIG_SLUB
 #define KMALLOC_SHIFT_HIGH	(PAGE_SHIFT + 1)
-#define KMALLOC_SHIFT_MAX	(MAX_ORDER + PAGE_SHIFT - 1)
+#define KMALLOC_SHIFT_MAX	(MAX_ORDER + PAGE_SHIFT)
 #ifndef KMALLOC_SHIFT_LOW
 #define KMALLOC_SHIFT_LOW	3
 #endif
@@ -305,7 +305,7 @@ static inline unsigned int arch_slab_minalign(void)
  * be allocated from the same page.
  */
 #define KMALLOC_SHIFT_HIGH	PAGE_SHIFT
-#define KMALLOC_SHIFT_MAX	(MAX_ORDER + PAGE_SHIFT - 1)
+#define KMALLOC_SHIFT_MAX	(MAX_ORDER + PAGE_SHIFT)
 #ifndef KMALLOC_SHIFT_LOW
 #define KMALLOC_SHIFT_LOW	3
 #endif