[PATCH v4 2/4] cma: fix counting of isolated pages

[Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>]

Isolated free pages shouldn't be accounted to NR_FREE_PAGES counter.
Fix it by properly decreasing/increasing NR_FREE_PAGES counter in
set_migratetype_isolate()/unset_migratetype_isolate() and removing
counter adjustment for isolated pages from free_one_page() and
split_free_page().

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 mm/page_alloc.c     |  9 +++++++--
 mm/page_isolation.c | 12 +++++++++---
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e9da55c..6a59e42 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -691,7 +691,8 @@ static void free_one_page(struct zone *zone, struct page *page, int order,
 	zone->pages_scanned = 0;
 
 	__free_one_page(page, zone, order, migratetype);
-	__mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
+	if (unlikely(migratetype != MIGRATE_ISOLATE))
+		__mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
 	spin_unlock(&zone->lock);
 }
 
@@ -1397,6 +1398,7 @@ int split_free_page(struct page *page, bool check_wmark)
 	unsigned int order;
 	unsigned long watermark;
 	struct zone *zone;
+	int mt;
 
 	BUG_ON(!PageBuddy(page));
 
@@ -1414,7 +1416,10 @@ int split_free_page(struct page *page, bool check_wmark)
 	list_del(&page->lru);
 	zone->free_area[order].nr_free--;
 	rmv_page_order(page);
-	__mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
+
+	mt = get_pageblock_migratetype(page);
+	if (unlikely(mt != MIGRATE_ISOLATE))
+		__mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
 
 	/* Split into individual pages */
 	set_page_refcounted(page);
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 247d1f1..3ca1716 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -76,8 +76,12 @@ int set_migratetype_isolate(struct page *page)
 
 out:
 	if (!ret) {
+		unsigned long nr_pages;
+
 		set_pageblock_isolate(page);
-		move_freepages_block(zone, page, MIGRATE_ISOLATE);
+		nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
+
+		__mod_zone_page_state(zone, NR_FREE_PAGES, -nr_pages);
 	}
 
 	spin_unlock_irqrestore(&zone->lock, flags);
@@ -89,12 +93,14 @@ out:
 void unset_migratetype_isolate(struct page *page, unsigned migratetype)
 {
 	struct zone *zone;
-	unsigned long flags;
+	unsigned long flags, nr_pages;
+
 	zone = page_zone(page);
 	spin_lock_irqsave(&zone->lock, flags);
 	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 		goto out;
-	move_freepages_block(zone, page, migratetype);
+	nr_pages = move_freepages_block(zone, page, migratetype);
+	__mod_zone_page_state(zone, NR_FREE_PAGES, nr_pages);
 	restore_pageblock_isolate(page, migratetype);
 out:
 	spin_unlock_irqrestore(&zone->lock, flags);
-- 
1.7.11.3

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