memcg swap: mem_cgroup_move_swap_account never needs fixup

The need_fixup arg to mem_cgroup_move_swap_account() is always false,
so just remove it.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -3165,7 +3165,6 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)
  * @entry: swap entry to be moved
  * @from:  mem_cgroup which the entry is moved from
  * @to:  mem_cgroup which the entry is moved to
- * @need_fixup: whether we should fixup res_counters and refcounts.
  *
  * It succeeds only when the swap_cgroup's record for this entry is the same
  * as the mem_cgroup's id of @from.
@@ -3176,7 +3175,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)
  * both res and memsw, and called css_get().
  */
 static int mem_cgroup_move_swap_account(swp_entry_t entry,
-		struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup)
+				struct mem_cgroup *from, struct mem_cgroup *to)
 {
 	unsigned short old_id, new_id;
 
@@ -3195,24 +3194,13 @@ static int mem_cgroup_move_swap_account(swp_entry_t entry,
 		 * swap-in, the refcount of @to might be decreased to 0.
 		 */
 		mem_cgroup_get(to);
-		if (need_fixup) {
-			if (!mem_cgroup_is_root(from))
-				res_counter_uncharge(&from->memsw, PAGE_SIZE);
-			mem_cgroup_put(from);
-			/*
-			 * we charged both to->res and to->memsw, so we should
-			 * uncharge to->res.
-			 */
-			if (!mem_cgroup_is_root(to))
-				res_counter_uncharge(&to->res, PAGE_SIZE);
-		}
 		return 0;
 	}
 	return -EINVAL;
 }
 #else
 static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
-		struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup)
+				struct mem_cgroup *from, struct mem_cgroup *to)
 {
 	return -EINVAL;
 }
@@ -5546,8 +5534,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 			break;
 		case MC_TARGET_SWAP:
 			ent = target.ent;
-			if (!mem_cgroup_move_swap_account(ent,
-						mc.from, mc.to, false)) {
+			if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to)) {
 				mc.precharge--;
 				/* we fixup refcnts and charges later. */
 				mc.moved_swap++;