memcg: create extensible page stat update routines

Replace usage of the mem_cgroup_update_file_mapped() memcg
statistic update routine with two new routines:
* mem_cgroup_inc_page_stat()
* mem_cgroup_dec_page_stat()

As before, only the file_mapped statistic is managed.  However, these more
general interfaces allow for new statistics to be more easily added.  New
statistics are added with memcg dirty page accounting.

Signed-off-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrea Righi <arighi@develer.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 9 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 741206ffdace..3d8a0c79dece 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1600,7 +1600,8 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
  * possibility of race condition. If there is, we take a lock.
  */
 
-static void mem_cgroup_update_file_stat(struct page *page, int idx, int val)
+void mem_cgroup_update_page_stat(struct page *page,
+                                 enum mem_cgroup_page_stat_item idx, int val)
 {
         struct mem_cgroup *mem;
         struct page_cgroup *pc = lookup_page_cgroup(page);
@@ -1623,30 +1624,27 @@ static void mem_cgroup_update_file_stat(struct page *page, int idx, int val)
                         goto out;
         }
 
-        this_cpu_add(mem->stat->count[idx], val);
-
         switch (idx) {
-        case MEM_CGROUP_STAT_FILE_MAPPED:
+        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:
                 BUG();
         }
 
+        this_cpu_add(mem->stat->count[idx], val);
+
 out:
         if (unlikely(need_unlock))
                 unlock_page_cgroup(pc);
         rcu_read_unlock();
         return;
 }
-
-void mem_cgroup_update_file_mapped(struct page *page, int val)
-{
-        mem_cgroup_update_file_stat(page, MEM_CGROUP_STAT_FILE_MAPPED, val);
-}
+EXPORT_SYMBOL(mem_cgroup_update_page_stat);
 
 /*
  * size of first charge trial. "32" comes from vmscan.c's magic value.