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, 7 insertions, 5 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 3f8fa06b963b..7f210f160990 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2000,7 +2000,7 @@ gotten:
         cow_user_page(new_page, old_page, address, vma);
         __SetPageUptodate(new_page);
 
-        if (mem_cgroup_charge(new_page, mm, GFP_KERNEL))
+        if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
                 goto oom_free_new;
 
         /*
@@ -2392,6 +2392,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
         struct page *page;
         swp_entry_t entry;
         pte_t pte;
+        struct mem_cgroup *ptr = NULL;
         int ret = 0;
 
         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
@@ -2430,7 +2431,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
         lock_page(page);
         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
 
-        if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
+        if (mem_cgroup_try_charge(mm, GFP_KERNEL, &ptr) == -ENOMEM) {
                 ret = VM_FAULT_OOM;
                 unlock_page(page);
                 goto out;
@@ -2460,6 +2461,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
         flush_icache_page(vma, page);
         set_pte_at(mm, address, page_table, pte);
         page_add_anon_rmap(page, vma, address);
+        mem_cgroup_commit_charge_swapin(page, ptr);
 
         swap_free(entry);
         if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
@@ -2480,7 +2482,7 @@ unlock:
 out:
         return ret;
 out_nomap:
-        mem_cgroup_uncharge_page(page);
+        mem_cgroup_cancel_charge_swapin(ptr);
         pte_unmap_unlock(page_table, ptl);
         unlock_page(page);
         page_cache_release(page);
@@ -2510,7 +2512,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 goto oom;
         __SetPageUptodate(page);
 
-        if (mem_cgroup_charge(page, mm, GFP_KERNEL))
+        if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))
                 goto oom_free_page;
 
         entry = mk_pte(page, vma->vm_page_prot);
@@ -2601,7 +2603,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                                 ret = VM_FAULT_OOM;
                                 goto out;
                         }
-                        if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
+                        if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
                                 ret = VM_FAULT_OOM;
                                 page_cache_release(page);
                                 goto out;