[PATCH 1/6] mm/page_alloc: fix same zone check in __pageblock_pfn_to_page()

[js1304]

From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

There is a system that node's pfn are overlapped like as following.

-----pfn-------->
N0 N1 N2 N0 N1 N2

Therefore, we need to care this overlapping when iterating pfn range.

In __pageblock_pfn_to_page(), there is a check for this but it's
not sufficient. This check cannot distinguish the case that zone id
is the same but node id is different. This patch fixes it.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
 mm/page_alloc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8120f07..93293b4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1173,8 +1173,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
 
 	end_page = pfn_to_page(end_pfn);
 
-	/* This gives a shorter code than deriving page_zone(end_page) */
-	if (page_zone_id(start_page) != page_zone_id(end_page))
+	if (zone != page_zone(end_page))
 		return NULL;
 
 	return start_page;
-- 
1.9.1