---

yaml
---
r: 308920
b: refs/heads/master
c: cc926f7
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d01dd17f1067ca50dbb9d1d3400d33221ce339e7
+refs/heads/master: cc926f78420705817b807dbec0c5d3643827eba3

trunk/Documentation/cgroups/memory.txt

@@ -376,14 +376,15 @@ cgroup might have some charge associated with it, even though all
 tasks have migrated away from it. (because we charge against pages, not
 against tasks.)
 
-Such charges are freed or moved to their parent. At moving, both of RSS
-and CACHES are moved to parent.
-rmdir() may return -EBUSY if freeing/moving fails. See 5.1 also.
+We move the stats to root (if use_hierarchy==0) or parent (if
+use_hierarchy==1), and no change on the charge except uncharging
+from the child.
 
 Charges recorded in swap information is not updated at removal of cgroup.
 Recorded information is discarded and a cgroup which uses swap (swapcache)
 will be charged as a new owner of it.
 
+About use_hierarchy, see Section 6.
 
 5. Misc. interfaces.
 
@@ -396,13 +397,15 @@ will be charged as a new owner of it.
 
   Almost all pages tracked by this memory cgroup will be unmapped and freed.
   Some pages cannot be freed because they are locked or in-use. Such pages are
-  moved to parent and this cgroup will be empty. This may return -EBUSY if
-  VM is too busy to free/move all pages immediately.
+  moved to parent(if use_hierarchy==1) or root (if use_hierarchy==0) and this
+  cgroup will be empty.
 
   Typical use case of this interface is that calling this before rmdir().
   Because rmdir() moves all pages to parent, some out-of-use page caches can be
   moved to the parent. If you want to avoid that, force_empty will be useful.
 
+  About use_hierarchy, see Section 6.
+
 5.2 stat file
 
 memory.stat file includes following statistics

trunk/mm/memcontrol.c

@@ -2678,15 +2678,13 @@ static int mem_cgroup_move_parent(struct page *page,
 				  struct mem_cgroup *child,
 				  gfp_t gfp_mask)
 {
-	struct cgroup *cg = child->css.cgroup;
-	struct cgroup *pcg = cg->parent;
 	struct mem_cgroup *parent;
 	unsigned int nr_pages;
 	unsigned long uninitialized_var(flags);
 	int ret;
 
 	/* Is ROOT ? */
-	if (!pcg)
+	if (mem_cgroup_is_root(child))
 		return -EINVAL;
 
 	ret = -EBUSY;
@@ -2697,33 +2695,23 @@ static int mem_cgroup_move_parent(struct page *page,
 
 	nr_pages = hpage_nr_pages(page);
 
-	parent = mem_cgroup_from_cont(pcg);
-	if (!parent->use_hierarchy) {
-		ret = __mem_cgroup_try_charge(NULL,
-					gfp_mask, nr_pages, &parent, false);
-		if (ret)
-			goto put_back;
-	}
+	parent = parent_mem_cgroup(child);
+	/*
+	 * If no parent, move charges to root cgroup.
+	 */
+	if (!parent)
+		parent = root_mem_cgroup;
 
 	if (nr_pages > 1)
 		flags = compound_lock_irqsave(page);
 
-	if (parent->use_hierarchy) {
-		ret = mem_cgroup_move_account(page, nr_pages,
-					pc, child, parent, false);
-		if (!ret)
-			__mem_cgroup_cancel_local_charge(child, nr_pages);
-	} else {
-		ret = mem_cgroup_move_account(page, nr_pages,
-					pc, child, parent, true);
-
-		if (ret)
-			__mem_cgroup_cancel_charge(parent, nr_pages);
-	}
+	ret = mem_cgroup_move_account(page, nr_pages,
+				pc, child, parent, false);
+	if (!ret)
+		__mem_cgroup_cancel_local_charge(child, nr_pages);
 
 	if (nr_pages > 1)
 		compound_unlock_irqrestore(page, flags);
-put_back:
 	putback_lru_page(page);
 put:
 	put_page(page);