[PATCH] Properly account for freed pages in free_pages_bulk() andwhen allocating high-order pages in buffered_rmqueue() V2

[Mel Gorman]

free_pages_bulk() updates the number of free pages in the zone but it is
assuming that the pages being freed are order-0. While this is currently
always true, it's wrong to assume the order is 0. This patch fixes the problem.

buffered_rmqueue() is not updating NR_FREE_PAGES when allocating pages with
__rmqueue(). As a result, high-order allocation will appear to increase
the number of free pages leading to the situation where the free page count
exceeds available RAM. This patch accounts for those allocated pages properly.

This is a fix for page-allocator-update-nr_free_pages-only-as-necessary.patch.

Changelog since V1
  o Change 1UL to 1 as it's unnecessary in this case to be unsigned long

Reported-by: Zhang, Yanmin <yanmin_zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
--- 
 mm/page_alloc.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5dd2d59..59eb2e1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -545,7 +545,7 @@ static void free_pages_bulk(struct zone *zone, int count,
 	zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
 	zone->pages_scanned = 0;
 
-	__mod_zone_page_state(zone, NR_FREE_PAGES, count);
+	__mod_zone_page_state(zone, NR_FREE_PAGES, count << order);
 	while (count--) {
 		struct page *page;
 
@@ -1151,6 +1151,7 @@ again:
 	} else {
 		spin_lock_irqsave(&zone->lock, flags);
 		page = __rmqueue(zone, order, migratetype);
+		__mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << order));
 		spin_unlock(&zone->lock);
 		if (!page)
 			goto failed;
--
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