mm, counters: remove task argument to sync_mm_rss() and __sync_task_rss_stat()

sync_mm_rss() can only be used for current to avoid race conditions in
iterating and clearing its per-task counters.  Remove the task argument
for it and its helper function, __sync_task_rss_stat(), to avoid thinking
it can be used safely for anything other than current.

Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memory.c b/mm/memory.c
index a5de734..2d27239 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -125,17 +125,17 @@
 
 #if defined(SPLIT_RSS_COUNTING)
 
-static void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm)
+static void __sync_task_rss_stat(struct mm_struct *mm)
 {
 	int i;
 
 	for (i = 0; i < NR_MM_COUNTERS; i++) {
-		if (task->rss_stat.count[i]) {
-			add_mm_counter(mm, i, task->rss_stat.count[i]);
-			task->rss_stat.count[i] = 0;
+		if (current->rss_stat.count[i]) {
+			add_mm_counter(mm, i, current->rss_stat.count[i]);
+			current->rss_stat.count[i] = 0;
 		}
 	}
-	task->rss_stat.events = 0;
+	current->rss_stat.events = 0;
 }
 
 static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
@@ -157,12 +157,12 @@
 	if (unlikely(task != current))
 		return;
 	if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
-		__sync_task_rss_stat(task, task->mm);
+		__sync_task_rss_stat(task->mm);
 }
 
-void sync_mm_rss(struct task_struct *task, struct mm_struct *mm)
+void sync_mm_rss(struct mm_struct *mm)
 {
-	__sync_task_rss_stat(task, mm);
+	__sync_task_rss_stat(mm);
 }
 #else /* SPLIT_RSS_COUNTING */
 
@@ -643,7 +643,7 @@
 	int i;
 
 	if (current->mm == mm)
-		sync_mm_rss(current, mm);
+		sync_mm_rss(mm);
 	for (i = 0; i < NR_MM_COUNTERS; i++)
 		if (rss[i])
 			add_mm_counter(mm, i, rss[i]);