mm, treewide: introduce NR_PAGE_ORDERS

NR_PAGE_ORDERS defines the number of page orders supported by the page
allocator, ranging from 0 to MAX_ORDER, MAX_ORDER + 1 in total.

NR_PAGE_ORDERS assists in defining arrays of page orders and allows for
more natural iteration over them.

[kirill.shutemov@linux.intel.com: fixup for kerneldoc warning]
  Link: https://lkml.kernel.org/r/20240101111512.7empzyifq7kxtzk3@box
Link: https://lkml.kernel.org/r/20231228144704.14033-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

15 files changed, 42 insertions, 41 deletions

diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index 78e4d2e7ba144..3f8769e46b07a 100644
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -172,7 +172,7 @@ variables.
 Offset of the free_list's member. This value is used to compute the number
 of free pages.
 
-Each zone has a free_area structure array called free_area[MAX_ORDER + 1].
+Each zone has a free_area structure array called free_area[NR_PAGE_ORDERS].
 The free_list represents a linked list of free page blocks.
 
 (list_head, next|prev)
@@ -189,8 +189,8 @@ Offsets of the vmap_area's members. They carry vmalloc-specific
 information. Makedumpfile gets the start address of the vmalloc region
 from this.
 
-(zone.free_area, MAX_ORDER + 1)
--------------------------------
+(zone.free_area, NR_PAGE_ORDERS)
+--------------------------------
 
 Free areas descriptor. User-space tools use this value to iterate the
 free_area ranges. MAX_ORDER is used by the zone buddy allocator.
diff --git a/arch/arm64/kvm/hyp/include/nvhe/gfp.h b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
index fe5472a184a37..97c527ef53c2a 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/gfp.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
@@ -16,7 +16,7 @@ struct hyp_pool {
 	 * API at EL2.
 	 */
 	hyp_spinlock_t lock;
-	struct list_head free_area[MAX_ORDER + 1];
+	struct list_head free_area[NR_PAGE_ORDERS];
 	phys_addr_t range_start;
 	phys_addr_t range_end;
 	unsigned short max_order;
diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
index 08ffd17d5ec34..523a6e5ee9251 100644
--- a/arch/sparc/kernel/traps_64.c
+++ b/arch/sparc/kernel/traps_64.c
@@ -897,7 +897,7 @@ void __init cheetah_ecache_flush_init(void)
 
 	/* Now allocate error trap reporting scoreboard. */
 	sz = NR_CPUS * (2 * sizeof(struct cheetah_err_info));
-	for (order = 0; order <= MAX_ORDER; order++) {
+	for (order = 0; order < NR_PAGE_ORDERS; order++) {
 		if ((PAGE_SIZE << order) >= sz)
 			break;
 	}
diff --git a/drivers/gpu/drm/ttm/tests/ttm_device_test.c b/drivers/gpu/drm/ttm/tests/ttm_device_test.c
index b1b423b68cdf1..19eaff22e6ae0 100644
--- a/drivers/gpu/drm/ttm/tests/ttm_device_test.c
+++ b/drivers/gpu/drm/ttm/tests/ttm_device_test.c
@@ -175,7 +175,7 @@ static void ttm_device_init_pools(struct kunit *test)
 
 	if (params->pools_init_expected) {
 		for (int i = 0; i < TTM_NUM_CACHING_TYPES; ++i) {
-			for (int j = 0; j <= MAX_ORDER; ++j) {
+			for (int j = 0; j < NR_PAGE_ORDERS; ++j) {
 				pt = pool->caching[i].orders[j];
 				KUNIT_EXPECT_PTR_EQ(test, pt.pool, pool);
 				KUNIT_EXPECT_EQ(test, pt.caching, i);
diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
index fe610a3cace00..d183bb97c526c 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -65,11 +65,11 @@ module_param(page_pool_size, ulong, 0644);
 
 static atomic_long_t allocated_pages;
 
-static struct ttm_pool_type global_write_combined[MAX_ORDER + 1];
-static struct ttm_pool_type global_uncached[MAX_ORDER + 1];
+static struct ttm_pool_type global_write_combined[NR_PAGE_ORDERS];
+static struct ttm_pool_type global_uncached[NR_PAGE_ORDERS];
 
-static struct ttm_pool_type global_dma32_write_combined[MAX_ORDER + 1];
-static struct ttm_pool_type global_dma32_uncached[MAX_ORDER + 1];
+static struct ttm_pool_type global_dma32_write_combined[NR_PAGE_ORDERS];
+static struct ttm_pool_type global_dma32_uncached[NR_PAGE_ORDERS];
 
 static spinlock_t shrinker_lock;
 static struct list_head shrinker_list;
@@ -568,7 +568,7 @@ void ttm_pool_init(struct ttm_pool *pool, struct device *dev,
 
 	if (use_dma_alloc || nid != NUMA_NO_NODE) {
 		for (i = 0; i < TTM_NUM_CACHING_TYPES; ++i)
-			for (j = 0; j <= MAX_ORDER; ++j)
+			for (j = 0; j < NR_PAGE_ORDERS; ++j)
 				ttm_pool_type_init(&pool->caching[i].orders[j],
 						   pool, i, j);
 	}
@@ -601,7 +601,7 @@ void ttm_pool_fini(struct ttm_pool *pool)
 
 	if (pool->use_dma_alloc || pool->nid != NUMA_NO_NODE) {
 		for (i = 0; i < TTM_NUM_CACHING_TYPES; ++i)
-			for (j = 0; j <= MAX_ORDER; ++j)
+			for (j = 0; j < NR_PAGE_ORDERS; ++j)
 				ttm_pool_type_fini(&pool->caching[i].orders[j]);
 	}
 
@@ -656,7 +656,7 @@ static void ttm_pool_debugfs_header(struct seq_file *m)
 	unsigned int i;
 
 	seq_puts(m, "\t ");
-	for (i = 0; i <= MAX_ORDER; ++i)
+	for (i = 0; i < NR_PAGE_ORDERS; ++i)
 		seq_printf(m, " ---%2u---", i);
 	seq_puts(m, "\n");
 }
@@ -667,7 +667,7 @@ static void ttm_pool_debugfs_orders(struct ttm_pool_type *pt,
 {
 	unsigned int i;
 
-	for (i = 0; i <= MAX_ORDER; ++i)
+	for (i = 0; i < NR_PAGE_ORDERS; ++i)
 		seq_printf(m, " %8u", ttm_pool_type_count(&pt[i]));
 	seq_puts(m, "\n");
 }
@@ -776,7 +776,7 @@ int ttm_pool_mgr_init(unsigned long num_pages)
 	spin_lock_init(&shrinker_lock);
 	INIT_LIST_HEAD(&shrinker_list);
 
-	for (i = 0; i <= MAX_ORDER; ++i) {
+	for (i = 0; i < NR_PAGE_ORDERS; ++i) {
 		ttm_pool_type_init(&global_write_combined[i], NULL,
 				   ttm_write_combined, i);
 		ttm_pool_type_init(&global_uncached[i], NULL, ttm_uncached, i);
@@ -816,7 +816,7 @@ void ttm_pool_mgr_fini(void)
 {
 	unsigned int i;
 
-	for (i = 0; i <= MAX_ORDER; ++i) {
+	for (i = 0; i < NR_PAGE_ORDERS; ++i) {
 		ttm_pool_type_fini(&global_write_combined[i]);
 		ttm_pool_type_fini(&global_uncached[i]);
 
diff --git a/include/drm/ttm/ttm_pool.h b/include/drm/ttm/ttm_pool.h
index 30a347e5aa114..4490d43c63e33 100644
--- a/include/drm/ttm/ttm_pool.h
+++ b/include/drm/ttm/ttm_pool.h
@@ -74,7 +74,7 @@ struct ttm_pool {
 	bool use_dma32;
 
 	struct {
-		struct ttm_pool_type orders[MAX_ORDER + 1];
+		struct ttm_pool_type orders[NR_PAGE_ORDERS];
 	} caching[TTM_NUM_CACHING_TYPES];
 };
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index c18c53353b50f..1ea7636dfb765 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -35,6 +35,8 @@
 
 #define IS_MAX_ORDER_ALIGNED(pfn) IS_ALIGNED(pfn, MAX_ORDER_NR_PAGES)
 
+#define NR_PAGE_ORDERS (MAX_ORDER + 1)
+
 /*
  * PAGE_ALLOC_COSTLY_ORDER is the order at which allocations are deemed
  * costly to service.  That is between allocation orders which should
@@ -96,7 +98,7 @@ 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 < NR_PAGE_ORDERS; order++) \
 		for (type = 0; type < MIGRATE_TYPES; type++)
 
 extern int page_group_by_mobility_disabled;
@@ -933,7 +935,7 @@ struct zone {
 	CACHELINE_PADDING(_pad1_);
 
 	/* free areas of different sizes */
-	struct free_area	free_area[MAX_ORDER + 1];
+	struct free_area	free_area[NR_PAGE_ORDERS];
 
 #ifdef CONFIG_UNACCEPTED_MEMORY
 	/* Pages to be accepted. All pages on the list are MAX_ORDER */
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index d4313b53837e3..56cf4ad7abbba 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -802,7 +802,7 @@ static int __init crash_save_vmcoreinfo_init(void)
 	VMCOREINFO_OFFSET(list_head, prev);
 	VMCOREINFO_OFFSET(vmap_area, va_start);
 	VMCOREINFO_OFFSET(vmap_area, list);
-	VMCOREINFO_LENGTH(zone.free_area, MAX_ORDER + 1);
+	VMCOREINFO_LENGTH(zone.free_area, NR_PAGE_ORDERS);
 	log_buf_vmcoreinfo_setup();
 	VMCOREINFO_LENGTH(free_area.free_list, MIGRATE_TYPES);
 	VMCOREINFO_NUMBER(NR_FREE_PAGES);
diff --git a/lib/test_meminit.c b/lib/test_meminit.c
index 0ae35223d7733..0dc173849a542 100644
--- a/lib/test_meminit.c
+++ b/lib/test_meminit.c
@@ -93,7 +93,7 @@ static int __init test_pages(int *total_failures)
 	int failures = 0, num_tests = 0;
 	int i;
 
-	for (i = 0; i <= MAX_ORDER; i++)
+	for (i = 0; i < NR_PAGE_ORDERS; i++)
 		num_tests += do_alloc_pages_order(i, &failures);
 
 	REPORT_FAILURES_IN_FN();
diff --git a/mm/compaction.c b/mm/compaction.c
index de15a2ef0af57..24f8eb4d62604 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2229,7 +2229,7 @@ static enum compact_result __compact_finished(struct compact_control *cc)
 
 	/* Direct compactor: Is a suitable page free? */
 	ret = COMPACT_NO_SUITABLE_PAGE;
-	for (order = cc->order; order <= MAX_ORDER; order++) {
+	for (order = cc->order; order < NR_PAGE_ORDERS; order++) {
 		struct free_area *area = &cc->zone->free_area[order];
 		bool can_steal;
 
diff --git a/mm/kmsan/init.c b/mm/kmsan/init.c
index ffedf4dbc49d7..103e2e88ea033 100644
--- a/mm/kmsan/init.c
+++ b/mm/kmsan/init.c
@@ -96,7 +96,7 @@ void __init kmsan_init_shadow(void)
 struct metadata_page_pair {
 	struct page *shadow, *origin;
 };
-static struct metadata_page_pair held_back[MAX_ORDER + 1] __initdata;
+static struct metadata_page_pair held_back[NR_PAGE_ORDERS] __initdata;
 
 /*
  * Eager metadata allocation. When the memblock allocator is freeing pages to
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5526797b7f960..ccecf6158ae43 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1560,7 +1560,7 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
 	struct page *page;
 
 	/* Find a page of the appropriate size in the preferred list */
-	for (current_order = order; current_order <= MAX_ORDER; ++current_order) {
+	for (current_order = order; current_order < NR_PAGE_ORDERS; ++current_order) {
 		area = &(zone->free_area[current_order]);
 		page = get_page_from_free_area(area, migratetype);
 		if (!page)
@@ -1934,7 +1934,7 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
 			continue;
 
 		spin_lock_irqsave(&zone->lock, flags);
-		for (order = 0; order <= MAX_ORDER; order++) {
+		for (order = 0; order < NR_PAGE_ORDERS; order++) {
 			struct free_area *area = &(zone->free_area[order]);
 
 			page = get_page_from_free_area(area, MIGRATE_HIGHATOMIC);
@@ -2044,8 +2044,7 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype,
 	return false;
 
 find_smallest:
-	for (current_order = order; current_order <= MAX_ORDER;
-							current_order++) {
+	for (current_order = order; current_order < NR_PAGE_ORDERS; current_order++) {
 		area = &(zone->free_area[current_order]);
 		fallback_mt = find_suitable_fallback(area, current_order,
 				start_migratetype, false, &can_steal);
@@ -3000,7 +2999,7 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
 		return true;
 
 	/* For a high-order request, check at least one suitable page is free */
-	for (o = order; o <= MAX_ORDER; o++) {
+	for (o = order; o < NR_PAGE_ORDERS; o++) {
 		struct free_area *area = &z->free_area[o];
 		int mt;
 
@@ -6628,7 +6627,7 @@ bool is_free_buddy_page(struct page *page)
 	unsigned long pfn = page_to_pfn(page);
 	unsigned int order;
 
-	for (order = 0; order <= MAX_ORDER; order++) {
+	for (order = 0; order < NR_PAGE_ORDERS; order++) {
 		struct page *page_head = page - (pfn & ((1 << order) - 1));
 
 		if (PageBuddy(page_head) &&
@@ -6683,7 +6682,7 @@ bool take_page_off_buddy(struct page *page)
 	bool ret = false;
 
 	spin_lock_irqsave(&zone->lock, flags);
-	for (order = 0; order <= MAX_ORDER; order++) {
+	for (order = 0; order < NR_PAGE_ORDERS; order++) {
 		struct page *page_head = page - (pfn & ((1 << order) - 1));
 		int page_order = buddy_order(page_head);
 
diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index b021f482a4cb3..66369cc5279bf 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -276,7 +276,7 @@ page_reporting_process_zone(struct page_reporting_dev_info *prdev,
 		return err;
 
 	/* Process each free list starting from lowest order/mt */
-	for (order = page_reporting_order; order <= MAX_ORDER; order++) {
+	for (order = page_reporting_order; order < NR_PAGE_ORDERS; order++) {
 		for (mt = 0; mt < MIGRATE_TYPES; mt++) {
 			/* We do not pull pages from the isolate free list */
 			if (is_migrate_isolate(mt))
diff --git a/mm/show_mem.c b/mm/show_mem.c
index ba0808d6917f9..8dcfafbd283c1 100644
--- a/mm/show_mem.c
+++ b/mm/show_mem.c
@@ -352,8 +352,8 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
 
 	for_each_populated_zone(zone) {
 		unsigned int order;
-		unsigned long nr[MAX_ORDER + 1], flags, total = 0;
-		unsigned char types[MAX_ORDER + 1];
+		unsigned long nr[NR_PAGE_ORDERS], flags, total = 0;
+		unsigned char types[NR_PAGE_ORDERS];
 
 		if (zone_idx(zone) > max_zone_idx)
 			continue;
@@ -363,7 +363,7 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
 		printk(KERN_CONT "%s: ", zone->name);
 
 		spin_lock_irqsave(&zone->lock, flags);
-		for (order = 0; order <= MAX_ORDER; order++) {
+		for (order = 0; order < NR_PAGE_ORDERS; order++) {
 			struct free_area *area = &zone->free_area[order];
 			int type;
 
@@ -377,7 +377,7 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
 			}
 		}
 		spin_unlock_irqrestore(&zone->lock, flags);
-		for (order = 0; order <= MAX_ORDER; order++) {
+		for (order = 0; order < NR_PAGE_ORDERS; order++) {
 			printk(KERN_CONT "%lu*%lukB ",
 			       nr[order], K(1UL) << order);
 			if (nr[order])
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 1437ca2f28c5f..03ead31c46a01 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1059,7 +1059,7 @@ static void fill_contig_page_info(struct zone *zone,
 	info->free_blocks_total = 0;
 	info->free_blocks_suitable = 0;
 
-	for (order = 0; order <= MAX_ORDER; order++) {
+	for (order = 0; order < NR_PAGE_ORDERS; order++) {
 		unsigned long blocks;
 
 		/*
@@ -1476,7 +1476,7 @@ static void frag_show_print(struct seq_file *m, pg_data_t *pgdat,
 	int order;
 
 	seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
-	for (order = 0; order <= MAX_ORDER; ++order)
+	for (order = 0; order < NR_PAGE_ORDERS; ++order)
 		/*
 		 * Access to nr_free is lockless as nr_free is used only for
 		 * printing purposes. Use data_race to avoid KCSAN warning.
@@ -1505,7 +1505,7 @@ static void pagetypeinfo_showfree_print(struct seq_file *m,
 					pgdat->node_id,
 					zone->name,
 					migratetype_names[mtype]);
-		for (order = 0; order <= MAX_ORDER; ++order) {
+		for (order = 0; order < NR_PAGE_ORDERS; ++order) {
 			unsigned long freecount = 0;
 			struct free_area *area;
 			struct list_head *curr;
@@ -1545,7 +1545,7 @@ static void pagetypeinfo_showfree(struct seq_file *m, void *arg)
 
 	/* Print header */
 	seq_printf(m, "%-43s ", "Free pages count per migrate type at order");
-	for (order = 0; order <= MAX_ORDER; ++order)
+	for (order = 0; order < NR_PAGE_ORDERS; ++order)
 		seq_printf(m, "%6d ", order);
 	seq_putc(m, '\n');
 
@@ -2181,7 +2181,7 @@ static void unusable_show_print(struct seq_file *m,
 	seq_printf(m, "Node %d, zone %8s ",
 				pgdat->node_id,
 				zone->name);
-	for (order = 0; order <= MAX_ORDER; ++order) {
+	for (order = 0; order < NR_PAGE_ORDERS; ++order) {
 		fill_contig_page_info(zone, order, &info);
 		index = unusable_free_index(order, &info);
 		seq_printf(m, "%d.%03d ", index / 1000, index % 1000);
@@ -2233,7 +2233,7 @@ static void extfrag_show_print(struct seq_file *m,
 	seq_printf(m, "Node %d, zone %8s ",
 				pgdat->node_id,
 				zone->name);
-	for (order = 0; order <= MAX_ORDER; ++order) {
+	for (order = 0; order < NR_PAGE_ORDERS; ++order) {
 		fill_contig_page_info(zone, order, &info);
 		index = __fragmentation_index(order, &info);
 		seq_printf(m, "%2d.%03d ", index / 1000, index % 1000);