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>

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>
Michal Hocko · Linus Torvalds
1 parent 9571a98290
Showing 1 changed file with 1 additions and 1 deletions Side-by-side Diff
mm/page_alloc.c
@@ -1525,7 +1525,7 @@
 	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)
...	...	@@ -1525,7 +1525,7 @@
1525	1525	long min = mark;
1526	1526	int o;
1527	1527
1528		- free_pages -= (1 << order) + 1;
	1528	+ free_pages -= (1 << order) - 1;
1529	1529	if (alloc_flags & ALLOC_HIGH)
1530	1530	min -= min / 2;
1531	1531	if (alloc_flags & ALLOC_HARDER)