[PATCH 1/13] memcg: avoid accounting special mapping

[KAMEZAWA Hiroyuki]

There are not-on-LRU pages which can be mapped and they are not worth to
be accounted. (becasue we can't shrink them and need dirty codes to handle
specical case) We don't want to account out-of-vm's-control pages.

When special_mapping_fault() is called, page->mapping is tend to be NULL 
and it's charged as Anonymous page. So avoid account it in __do_fault().
We can know that by checking anon var.
insert_page() also handles some special pages from drivers.

Changelog:
  - new patch.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

 mm/memory.c |   18 ++++++------------
 mm/rmap.c   |    4 ++--
 2 files changed, 8 insertions(+), 14 deletions(-)

Index: mmotm-2.6.27-rc6+/mm/memory.c
===================================================================
--- mmotm-2.6.27-rc6+.orig/mm/memory.c
+++ mmotm-2.6.27-rc6+/mm/memory.c
@@ -1323,18 +1323,14 @@ static int insert_page(struct vm_area_st
 	pte_t *pte;
 	spinlock_t *ptl;
 
-	retval = mem_cgroup_charge(page, mm, GFP_KERNEL);
-	if (retval)
-		goto out;
-
 	retval = -EINVAL;
 	if (PageAnon(page))
-		goto out_uncharge;
+		goto out;
 	retval = -ENOMEM;
 	flush_dcache_page(page);
 	pte = get_locked_pte(mm, addr, &ptl);
 	if (!pte)
-		goto out_uncharge;
+		goto out;
 	retval = -EBUSY;
 	if (!pte_none(*pte))
 		goto out_unlock;
@@ -1350,8 +1346,6 @@ static int insert_page(struct vm_area_st
 	return retval;
 out_unlock:
 	pte_unmap_unlock(pte, ptl);
-out_uncharge:
-	mem_cgroup_uncharge_page(page);
 out:
 	return retval;
 }
@@ -2542,7 +2536,7 @@ static int __do_fault(struct mm_struct *
 
 	}
 
-	if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
+	if (anon && mem_cgroup_charge(page, mm, GFP_KERNEL)) {
 		ret = VM_FAULT_OOM;
 		goto out;
 	}
@@ -2584,10 +2578,10 @@ static int __do_fault(struct mm_struct *
 		/* no need to invalidate: a not-present page won't be cached */
 		update_mmu_cache(vma, address, entry);
 	} else {
-		mem_cgroup_uncharge_page(page);
-		if (anon)
+		if (anon) {
+			mem_cgroup_uncharge_page(page);
 			page_cache_release(page);
-		else
+		} else
 			anon = 1; /* no anon but release faulted_page */
 	}
 
Index: mmotm-2.6.27-rc6+/mm/rmap.c
===================================================================
--- mmotm-2.6.27-rc6+.orig/mm/rmap.c
+++ mmotm-2.6.27-rc6+/mm/rmap.c
@@ -725,8 +725,8 @@ void page_remove_rmap(struct page *page,
 			page_clear_dirty(page);
 			set_page_dirty(page);
 		}
-
-		mem_cgroup_uncharge_page(page);
+		if (PageAnon(page))
+			mem_cgroup_uncharge_page(page);
 		__dec_zone_page_state(page,
 			PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
 		/*

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