[PATCH RESEND 3/4] memcg: move page-freeing code out of lock

[Namhyung Kim <namhyung@gmail.com>]

Move page-freeing code out of swap_cgroup_mutex in the hope that it
could reduce few of theoretical contentions between swapons and/or
swapoffs.

This is just a cleanup, no functional changes.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/page_cgroup.c |   22 +++++++++++++---------
 1 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index e7208105203c..9223bb48e80f 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -492,8 +492,8 @@ int swap_cgroup_swapon(int type, unsigned long max_pages)
 		/* memory shortage */
 		ctrl->map = NULL;
 		ctrl->length = 0;
-		vfree(array);
 		mutex_unlock(&swap_cgroup_mutex);
+		vfree(array);
 		goto nomem;
 	}
 	mutex_unlock(&swap_cgroup_mutex);
@@ -508,7 +508,8 @@ nomem:
 
 void swap_cgroup_swapoff(int type)
 {
-	int i;
+	struct page **map;
+	unsigned long i, length;
 	struct swap_cgroup_ctrl *ctrl;
 
 	if (!do_swap_account)
@@ -516,17 +517,20 @@ void swap_cgroup_swapoff(int type)
 
 	mutex_lock(&swap_cgroup_mutex);
 	ctrl = &swap_cgroup_ctrl[type];
-	if (ctrl->map) {
-		for (i = 0; i < ctrl->length; i++) {
-			struct page *page = ctrl->map[i];
+	map = ctrl->map;
+	length = ctrl->length;
+	ctrl->map = NULL;
+	ctrl->length = 0;
+	mutex_unlock(&swap_cgroup_mutex);
+
+	if (map) {
+		for (i = 0; i < length; i++) {
+			struct page *page = map[i];
 			if (page)
 				__free_page(page);
 		}
-		vfree(ctrl->map);
-		ctrl->map = NULL;
-		ctrl->length = 0;
+		vfree(map);
 	}
-	mutex_unlock(&swap_cgroup_mutex);
 }
 
 #endif
-- 
1.7.4

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