memcg: fix mapcount check in move charge code for anonymous page

Currently the charge on shared anonyous pages is supposed not to moved in
task migration.  To implement this, we need to check that mapcount > 1,
instread of > 2.  So this patch fixes it.

Signed-off-by: Naoya Horiguchi <[email protected]>
Reviewed-by: Daisuke Nishimura <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d0e57a3cda1899c156274d53e49e11be42957f87..5585dc3d36466189b0d89adf8e86f424372bdd23 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5075,7 +5075,7 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
                return NULL;
        if (PageAnon(page)) {
                /* we don't move shared anon */
-               if (!move_anon() || page_mapcount(page) > 2)
+               if (!move_anon() || page_mapcount(page) > 1)
                        return NULL;
        } else if (!move_file())
                /* we ignore mapcount for file pages */