[PATCH 1/12] memcg avoid accounting special mappings not on LRU

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

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'd like to make use of usual objrmap/radix-tree's protcol
and 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.
insert_page() also handles some special pages from drivers.

This patch is for avoiding to account special pages.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

 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);
 		/*