memcg: fix off-by-one when calculating swap cgroup map length

It allocated one more page than necessary if @max_pages was a multiple of
SC_PER_PAGE.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 4eb05302e2e1..5524e8bd7437 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -475,7 +475,7 @@ int swap_cgroup_swapon(int type, unsigned long max_pages)
         if (!do_swap_account)
                 return 0;
 
-        length = ((max_pages/SC_PER_PAGE) + 1);
+        length = DIV_ROUND_UP(max_pages, SC_PER_PAGE);
         array_size = length * sizeof(void *);
 
         array = vmalloc(array_size);