memcg: introduce charge-commit-cancel style of functions

There is a small race in do_swap_page().  When the page swapped-in is
charged, the mapcount can be greater than 0.  But, at the same time some
process (shares it ) call unmap and make mapcount 1->0 and the page is
uncharged.

      CPUA 			CPUB
       mapcount == 1.
   (1) charge if mapcount==0     zap_pte_range()
                                (2) mapcount 1 => 0.
			        (3) uncharge(). (success)
   (4) set page's rmap()
       mapcount 0=>1

Then, this swap page's account is leaked.

For fixing this, I added a new interface.
  - charge
   account to res_counter by PAGE_SIZE and try to free pages if necessary.
  - commit
   register page_cgroup and add to LRU if necessary.
  - cancel
   uncharge PAGE_SIZE because of do_swap_page failure.

     CPUA
  (1) charge (always)
  (2) set page's rmap (mapcount > 0)
  (3) commit charge was necessary or not after set_pte().

This protocol uses PCG_USED bit on page_cgroup for avoiding over accounting.
Usual mem_cgroup_charge_common() does charge -> commit at a time.

And this patch also adds following function to clarify all charges.

  - mem_cgroup_newpage_charge() ....replacement for mem_cgroup_charge()
	called against newly allocated anon pages.

  - mem_cgroup_charge_migrate_fixup()
        called only from remove_migration_ptes().
	we'll have to rewrite this later.(this patch just keeps old behavior)
	This function will be removed by additional patch to make migration
	clearer.

Good for clarifying "what we do"

Then, we have 4 following charge points.
  - newpage
  - swap-in
  - add-to-cache.
  - migration.

[akpm@linux-foundation.org: add missing inline directives to stubs]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 34 insertions, 2 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 1fbe14d3952..c592f315cd0 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -27,8 +27,17 @@ struct mm_struct;
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
 
-extern int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
+extern int mem_cgroup_newpage_charge(struct page *page, struct mm_struct *mm,
 				gfp_t gfp_mask);
+extern int mem_cgroup_charge_migrate_fixup(struct page *page,
+				struct mm_struct *mm, gfp_t gfp_mask);
+/* for swap handling */
+extern int mem_cgroup_try_charge(struct mm_struct *mm,
+		gfp_t gfp_mask, struct mem_cgroup **ptr);
+extern void mem_cgroup_commit_charge_swapin(struct page *page,
+					struct mem_cgroup *ptr);
+extern void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *ptr);
+
 extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 					gfp_t gfp_mask);
 extern void mem_cgroup_move_lists(struct page *page, enum lru_list lru);
@@ -71,7 +80,9 @@ extern long mem_cgroup_calc_reclaim(struct mem_cgroup *mem, struct zone *zone,
 
 
 #else /* CONFIG_CGROUP_MEM_RES_CTLR */
-static inline int mem_cgroup_charge(struct page *page,
+struct mem_cgroup;
+
+static inline int mem_cgroup_newpage_charge(struct page *page,
 					struct mm_struct *mm, gfp_t gfp_mask)
 {
 	return 0;
@@ -83,6 +94,27 @@ static inline int mem_cgroup_cache_charge(struct page *page,
 	return 0;
 }
 
+static inline int mem_cgroup_charge_migrate_fixup(struct page *page,
+					struct mm_struct *mm, gfp_t gfp_mask)
+{
+	return 0;
+}
+
+static inline int mem_cgroup_try_charge(struct mm_struct *mm,
+				gfp_t gfp_mask, struct mem_cgroup **ptr)
+{
+	return 0;
+}
+
+static inline void mem_cgroup_commit_charge_swapin(struct page *page,
+					  struct mem_cgroup *ptr)
+{
+}
+
+static inline void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *ptr)
+{
+}
+
 static inline void mem_cgroup_uncharge_page(struct page *page)
 {
 }