[RFC PATCH 6/9] use atomic for free_area[order].nr_free

[Aaron Lu]

Since we will make free path run concurrently, free_area[].nr_free has
to be atomic.

Signed-off-by: Aaron Lu <aaron...@intel.com>
---
 include/linux/mmzone.h |  2 +-
 mm/page_alloc.c        | 12 ++++++------
 mm/vmstat.c            |  4 ++--
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 84cfa56e2d19..e66b8c63d5d1 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -95,7 +95,7 @@ extern int page_group_by_mobility_disabled;
 
 struct free_area {
        struct list_head        free_list[MIGRATE_TYPES];
-       unsigned long           nr_free;
+       atomic_long_t           nr_free;
 };
 
 struct pglist_data;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d0b954783f1d..dff3edc60d71 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -701,7 +701,7 @@ static inline void add_to_buddy_common(struct page *page, 
struct zone *zone,
                                        unsigned int order)
 {
        set_page_order(page, order);
-       zone->free_area[order].nr_free++;
+       atomic_long_inc(&zone->free_area[order].nr_free);
 }
 
 static inline void add_to_buddy_head(struct page *page, struct zone *zone,
@@ -728,7 +728,7 @@ static inline void remove_from_buddy(struct page *page, 
struct zone *zone,
                                        unsigned int order)
 {
        list_del(&page->lru);
-       zone->free_area[order].nr_free--;
+       atomic_long_dec(&zone->free_area[order].nr_free);
        rmv_page_order(page);
 }
 
@@ -2225,7 +2225,7 @@ int find_suitable_fallback(struct free_area *area, 
unsigned int order,
        int i;
        int fallback_mt;
 
-       if (area->nr_free == 0)
+       if (atomic_long_read(&area->nr_free) == 0)
                return -1;
 
        *can_steal = false;
@@ -3178,7 +3178,7 @@ bool __zone_watermark_ok(struct zone *z, unsigned int 
order, unsigned long mark,
                struct free_area *area = &z->free_area[o];
                int mt;
 
-               if (!area->nr_free)
+               if (atomic_long_read(&area->nr_free) == 0)
                        continue;
 
                for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
@@ -5029,7 +5029,7 @@ void show_free_areas(unsigned int filter, nodemask_t 
*nodemask)
                        struct free_area *area = &zone->free_area[order];
                        int type;
 
-                       nr[order] = area->nr_free;
+                       nr[order] = atomic_long_read(&area->nr_free);
                        total += nr[order] << order;
 
                        types[order] = 0;
@@ -5562,7 +5562,7 @@ 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]);
-               zone->free_area[order].nr_free = 0;
+               atomic_long_set(&zone->free_area[order].nr_free, 0);
        }
 }
 
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 06d79271a8ae..c1985550bb9f 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1030,7 +1030,7 @@ static void fill_contig_page_info(struct zone *zone,
                unsigned long blocks;
 
                /* Count number of free blocks */
-               blocks = zone->free_area[order].nr_free;
+               blocks = atomic_long_read(&zone->free_area[order].nr_free);
                info->free_blocks_total += blocks;
 
                /* Count free base pages */
@@ -1353,7 +1353,7 @@ static void frag_show_print(struct seq_file *m, pg_data_t 
*pgdat,
 
        seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
        for (order = 0; order < MAX_ORDER; ++order)
-               seq_printf(m, "%6lu ", zone->free_area[order].nr_free);
+               seq_printf(m, "%6lu ", 
atomic_long_read(&zone->free_area[order].nr_free));
        seq_putc(m, '\n');
 }
 
-- 
2.17.1