memcg: remove mem_cgroup_uncharge

Nothing uses mem_cgroup_uncharge apart from mem_cgroup_uncharge_page, (a
trivial wrapper around it) and mem_cgroup_end_migration (which does the same
as mem_cgroup_uncharge_page).  And it often ends up having to lock just to let
its caller unlock.  Remove it (but leave the silly locking until a later
patch).

Moved mem_cgroup_cache_charge next to mem_cgroup_charge in memcontrol.h.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: David Rientjes <rientjes@google.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hirokazu Takahashi <taka@valinux.co.jp>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 15 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 83ba13ad31e1..1333d25163bb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -697,20 +697,22 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 
 /*
  * Uncharging is always a welcome operation, we never complain, simply
- * uncharge. This routine should be called with lock_page_cgroup held
+ * uncharge.
  */
-void mem_cgroup_uncharge(struct page_cgroup *pc)
+void mem_cgroup_uncharge_page(struct page *page)
 {
+        struct page_cgroup *pc;
         struct mem_cgroup *mem;
         struct mem_cgroup_per_zone *mz;
-        struct page *page;
         unsigned long flags;
 
         /*
          * Check if our page_cgroup is valid
          */
+        lock_page_cgroup(page);
+        pc = page_get_page_cgroup(page);
         if (!pc)
-                return;
+                goto unlock;
 
         if (atomic_dec_and_test(&pc->ref_cnt)) {
                 page = pc->page;
@@ -731,12 +733,8 @@ void mem_cgroup_uncharge(struct page_cgroup *pc)
                 }
                 lock_page_cgroup(page);
         }
-}
 
-void mem_cgroup_uncharge_page(struct page *page)
-{
-        lock_page_cgroup(page);
-        mem_cgroup_uncharge(page_get_page_cgroup(page));
+unlock:
         unlock_page_cgroup(page);
 }
 
@@ -759,12 +757,7 @@ int mem_cgroup_prepare_migration(struct page *page)
 
 void mem_cgroup_end_migration(struct page *page)
 {
-        struct page_cgroup *pc;
-
-        lock_page_cgroup(page);
-        pc = page_get_page_cgroup(page);
-        mem_cgroup_uncharge(pc);
-        unlock_page_cgroup(page);
+        mem_cgroup_uncharge_page(page);
 }
 /*
  * We know both *page* and *newpage* are now not-on-LRU and Pg_locked.