[PATCH RFC 06/19] mm: introduce for_each_free_list()

[Brendan Jackman <jackmanb@google.com>]

Later patches will rearrange the free areas, but there are a couple of
places that iterate over them with the assumption that they have the
current structure.

It seems ideally, code outside of mm should not be directly aware of
struct free_area in the first place, but that awareness seems relatively
harmless so just make the minimal change.

Now instead of letting users manually iterate over the free lists, just
provide a macro to do that. Then adopt that macro in a couple of places.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 include/linux/mmzone.h  |  7 +++++--
 kernel/power/snapshot.c |  8 ++++----
 mm/mm_init.c            | 11 +++++++----
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3e51190a55e4c..fc4d499fbbd2b 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -123,9 +123,12 @@ static inline bool migratetype_is_mergeable(int mt)
 	return mt < MIGRATE_PCPTYPES;
 }
 
-#define for_each_migratetype_order(order, type) \
+#define for_each_free_list(list, zone, order) \
 	for (order = 0; order < NR_PAGE_ORDERS; order++) \
-		for (type = 0; type < MIGRATE_TYPES; type++)
+		for (unsigned int type = 0; \
+		     list = &zone->free_area[order].free_list[type], \
+		     type < MIGRATE_TYPES; \
+		     type++) \
 
 extern int page_group_by_mobility_disabled;
 
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 0a946932d5c17..29a053d447c31 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1244,8 +1244,9 @@ unsigned int snapshot_additional_pages(struct zone *zone)
 static void mark_free_pages(struct zone *zone)
 {
 	unsigned long pfn, max_zone_pfn, page_count = WD_PAGE_COUNT;
+	struct list_head *free_list;
 	unsigned long flags;
-	unsigned int order, t;
+	unsigned int order;
 	struct page *page;
 
 	if (zone_is_empty(zone))
@@ -1269,9 +1270,8 @@ static void mark_free_pages(struct zone *zone)
 			swsusp_unset_page_free(page);
 	}
 
-	for_each_migratetype_order(order, t) {
-		list_for_each_entry(page,
-				&zone->free_area[order].free_list[t], buddy_list) {
+	for_each_free_list(free_list, zone, order) {
+		list_for_each_entry(page, free_list, buddy_list) {
 			unsigned long i;
 
 			pfn = page_to_pfn(page);
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 61d983d23f553..a748fb6d6555d 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1432,11 +1432,14 @@ static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx,
 
 static void __meminit zone_init_free_lists(struct zone *zone)
 {
-	unsigned int order, t;
-	for_each_migratetype_order(order, t) {
-		INIT_LIST_HEAD(&zone->free_area[order].free_list[t]);
+	struct list_head *list;
+	unsigned int order;
+
+	for_each_free_list(list, zone, order)
+		INIT_LIST_HEAD(list);
+
+	for (order = 0; order < NR_PAGE_ORDERS; order++)
 		zone->free_area[order].nr_free = 0;
-	}
 
 #ifdef CONFIG_UNACCEPTED_MEMORY
 	INIT_LIST_HEAD(&zone->unaccepted_pages);

-- 
2.51.2