memcg: add mem_cgroup_cancel_charge()

There are some places calling both res_counter_uncharge() and css_put() to
cancel the charge and the refcnt we have got by mem_cgroup_tyr_charge().

This patch introduces mem_cgroup_cancel_charge() and call it in those
places.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 20 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0b3efb843a8..2d6b4a912a6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1500,6 +1500,21 @@ nomem:
 }
 
 /*
+ * Somemtimes we have to undo a charge we got by try_charge().
+ * This function is for that and do uncharge, put css's refcnt.
+ * gotten by try_charge().
+ */
+static void mem_cgroup_cancel_charge(struct mem_cgroup *mem)
+{
+        if (!mem_cgroup_is_root(mem)) {
+                res_counter_uncharge(&mem->res, PAGE_SIZE);
+                if (do_swap_account)
+                        res_counter_uncharge(&mem->memsw, PAGE_SIZE);
+        }
+        css_put(&mem->css);
+}
+
+/*
  * A helper function to get mem_cgroup from ID. must be called under
  * rcu_read_lock(). The caller must check css_is_removed() or some if
  * it's concern. (dropping refcnt from swap can be called against removed
@@ -1565,12 +1580,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
         lock_page_cgroup(pc);
         if (unlikely(PageCgroupUsed(pc))) {
                 unlock_page_cgroup(pc);
-                if (!mem_cgroup_is_root(mem)) {
-                        res_counter_uncharge(&mem->res, PAGE_SIZE);
-                        if (do_swap_account)
-                                res_counter_uncharge(&mem->memsw, PAGE_SIZE);
-                }
-                css_put(&mem->css);
+                mem_cgroup_cancel_charge(mem);
                 return;
         }
 
@@ -1734,14 +1744,7 @@ static int mem_cgroup_move_parent(struct page_cgroup *pc,
 cancel:
         put_page(page);
 uncharge:
-        /* drop extra refcnt by try_charge() */
-        css_put(&parent->css);
-        /* uncharge if move fails */
-        if (!mem_cgroup_is_root(parent)) {
-                res_counter_uncharge(&parent->res, PAGE_SIZE);
-                if (do_swap_account)
-                        res_counter_uncharge(&parent->memsw, PAGE_SIZE);
-        }
+        mem_cgroup_cancel_charge(parent);
         return ret;
 }
 
@@ -1958,12 +1961,7 @@ void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem)
                 return;
         if (!mem)
                 return;
-        if (!mem_cgroup_is_root(mem)) {
-                res_counter_uncharge(&mem->res, PAGE_SIZE);
-                if (do_swap_account)
-                        res_counter_uncharge(&mem->memsw, PAGE_SIZE);
-        }
-        css_put(&mem->css);
+        mem_cgroup_cancel_charge(mem);
 }
 
 static void