From: Michal Hocko <mhocko@suse.cz>
Date: Tue, 10 Jan 2012 23:08:02 +0000 (-0800)
Subject: mm: fix off-by-two in __zone_watermark_ok()
X-Git-Tag: v3.3-rc1~113^2~95
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=df0a6daa01fa3856c08f4274d4f21a8092caa480;p=linux.git

mm: fix off-by-two in __zone_watermark_ok()

Commit 88f5acf88ae6 ("mm: page allocator: adjust the per-cpu counter
threshold when memory is low") changed the form how free_pages is
calculated but it forgot that we used to do free_pages - ((1 << order) -
1) so we ended up with off-by-two when calculating free_pages.

Reported-by: Wang Sheng-Hui <shhuiw@gmail.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4f95bcf0f2b1..59153da58c69 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1525,7 +1525,7 @@ static bool __zone_watermark_ok(struct zone *z, int order, unsigned long mark,
 	long min = mark;
 	int o;
 
-	free_pages -= (1 << order) + 1;
+	free_pages -= (1 << order) - 1;
 	if (alloc_flags & ALLOC_HIGH)
 		min -= min / 2;
 	if (alloc_flags & ALLOC_HARDER)