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>

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 5524e8bd74378cbbf4cc63727c4a04407ba8918f..74ccff61d1bea8d6e258170280ea5b20523dad23 100644 (file)
--- 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