memcg: move page-freeing code out of lock

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>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 9 deletions

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 5524e8bd7437..74ccff61d1be 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