memcg: remove PCG_FILE_MAPPED

With the new lock scheme for updating memcg's page stat, we don't need a
flag PCG_FILE_MAPPED which was duplicated information of page_mapped().

[hughd@google.com: cosmetic fix]
[hughd@google.com: add comment to MEM_CGROUP_CHARGE_TYPE_MAPPED case in __mem_cgroup_uncharge_common()]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Greg Thelen <gthelen@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 5 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index df1e180f6c30..0e13b2aeea61 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1966,10 +1966,6 @@ void mem_cgroup_update_page_stat(struct page *page,
 
         switch (idx) {
         case MEMCG_NR_FILE_MAPPED:
-                if (val > 0)
-                        SetPageCgroupFileMapped(pc);
-                else if (!page_mapped(page))
-                        ClearPageCgroupFileMapped(pc);
                 idx = MEM_CGROUP_STAT_FILE_MAPPED;
                 break;
         default:
@@ -2617,7 +2613,7 @@ static int mem_cgroup_move_account(struct page *page,
 
         move_lock_mem_cgroup(from, &flags);
 
-        if (PageCgroupFileMapped(pc)) {
+        if (!anon && page_mapped(page)) {
                 /* Update mapped_file data for mem_cgroup */
                 preempt_disable();
                 __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
@@ -2982,6 +2978,11 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
 
         switch (ctype) {
         case MEM_CGROUP_CHARGE_TYPE_MAPPED:
+                /*
+                 * Generally PageAnon tells if it's the anon statistics to be
+                 * updated; but sometimes e.g. mem_cgroup_uncharge_page() is
+                 * used before page reached the stage of being marked PageAnon.
+                 */
                 anon = true;
                 /* fallthrough */
         case MEM_CGROUP_CHARGE_TYPE_DROP: