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

Commit 88f5acf ("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 <[email protected]> Signed-off-by: Michal Hocko <[email protected]> Acked-by: Mel Gorman <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
leemgs · Jan 11, 2012 · df0a6da · df0a6da
1 parent 9571a98
commit df0a6da
Showing 1 changed file with 1 addition and 1 deletion.
diff --git 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)