From 3cf98d1b117203c4fc908b6ff9db822130cf0eb1 Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Date: Mon, 15 Mar 2010 00:34:57 -0400
Subject: [PATCH] --- yaml --- r: 188103 b: refs/heads/master c:
 e9e58a4ec3b1086d1ed8c915311aef1ae55454fd h: refs/heads/master i:   188101:
 db2ea227637c0d24b8386774a0039fa3e7c2b872   188099:
 26db5e81208abd10f416cda1cf849433e860f554   188095:
 5471ef9732533e9f3bf065804ffde09273dccff4 v: v3

---
 [refs]                 |  2 +-
 trunk/mm/page_cgroup.c | 20 ++++++++++++++++----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/[refs] b/[refs]
index e3d2ca40bacb..70e9c789b0ad 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a3d3203e4bb40f253b1541e310dc0f9305be7c84
+refs/heads/master: e9e58a4ec3b1086d1ed8c915311aef1ae55454fd
diff --git a/trunk/mm/page_cgroup.c b/trunk/mm/page_cgroup.c
index 3dd88539a0e6..6c0081441a32 100644
--- a/trunk/mm/page_cgroup.c
+++ b/trunk/mm/page_cgroup.c
@@ -284,6 +284,7 @@ static DEFINE_MUTEX(swap_cgroup_mutex);
 struct swap_cgroup_ctrl {
 	struct page **map;
 	unsigned long length;
+	spinlock_t	lock;
 };
 
 struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];
@@ -353,16 +354,22 @@ unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
 	struct swap_cgroup_ctrl *ctrl;
 	struct page *mappage;
 	struct swap_cgroup *sc;
+	unsigned long flags;
+	unsigned short retval;
 
 	ctrl = &swap_cgroup_ctrl[type];
 
 	mappage = ctrl->map[idx];
 	sc = page_address(mappage);
 	sc += pos;
-	if (cmpxchg(&sc->id, old, new) == old)
-		return old;
+	spin_lock_irqsave(&ctrl->lock, flags);
+	retval = sc->id;
+	if (retval == old)
+		sc->id = new;
 	else
-		return 0;
+		retval = 0;
+	spin_unlock_irqrestore(&ctrl->lock, flags);
+	return retval;
 }
 
 /**
@@ -383,13 +390,17 @@ unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
 	struct page *mappage;
 	struct swap_cgroup *sc;
 	unsigned short old;
+	unsigned long flags;
 
 	ctrl = &swap_cgroup_ctrl[type];
 
 	mappage = ctrl->map[idx];
 	sc = page_address(mappage);
 	sc += pos;
-	old = xchg(&sc->id, id);
+	spin_lock_irqsave(&ctrl->lock, flags);
+	old = sc->id;
+	sc->id = id;
+	spin_unlock_irqrestore(&ctrl->lock, flags);
 
 	return old;
 }
@@ -441,6 +452,7 @@ int swap_cgroup_swapon(int type, unsigned long max_pages)
 	mutex_lock(&swap_cgroup_mutex);
 	ctrl->length = length;
 	ctrl->map = array;
+	spin_lock_init(&ctrl->lock);
 	if (swap_cgroup_prepare(type)) {
 		/* memory shortage */
 		ctrl->map = NULL;