From 4432e2323b10393835423fe00be334131dad81fb Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Thu, 20 Jan 2011 14:44:31 -0800
Subject: [PATCH] --- yaml --- r: 232023 b: refs/heads/master c:
 713735b4233fad3ae35b5cad656baa41413887ca h: refs/heads/master i:   232021:
 0f609ab7b738189bd4ae72de9799b8b9f50bcc63   232019:
 149806b14a1dc9f2fae7dd2e0731a1e2b2f366c0   232015:
 d0f66b647c7caea25beec6de02c9d834ab8dcf2d v: v3

---
 [refs]                |  2 +-
 trunk/mm/memcontrol.c | 27 +++++++++------------------
 2 files changed, 10 insertions(+), 19 deletions(-)

diff --git a/[refs] b/[refs]
index 2fcd19784789..8881ce6b0d96 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2550326ac7a062fdfc204f9a3b98bdb9179638fc
+refs/heads/master: 713735b4233fad3ae35b5cad656baa41413887ca
diff --git a/trunk/mm/memcontrol.c b/trunk/mm/memcontrol.c
index 5b562b375cbd..db76ef726293 100644
--- a/trunk/mm/memcontrol.c
+++ b/trunk/mm/memcontrol.c
@@ -836,13 +836,12 @@ void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
 		return;
 
 	pc = lookup_page_cgroup(page);
-	/*
-	 * Used bit is set without atomic ops but after smp_wmb().
-	 * For making pc->mem_cgroup visible, insert smp_rmb() here.
-	 */
-	smp_rmb();
 	/* unused or root page is not rotated. */
-	if (!PageCgroupUsed(pc) || mem_cgroup_is_root(pc->mem_cgroup))
+	if (!PageCgroupUsed(pc))
+		return;
+	/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
+	smp_rmb();
+	if (mem_cgroup_is_root(pc->mem_cgroup))
 		return;
 	mz = page_cgroup_zoneinfo(pc);
 	list_move(&pc->lru, &mz->lists[lru]);
@@ -857,14 +856,10 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
 		return;
 	pc = lookup_page_cgroup(page);
 	VM_BUG_ON(PageCgroupAcctLRU(pc));
-	/*
-	 * Used bit is set without atomic ops but after smp_wmb().
-	 * For making pc->mem_cgroup visible, insert smp_rmb() here.
-	 */
-	smp_rmb();
 	if (!PageCgroupUsed(pc))
 		return;
-
+	/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
+	smp_rmb();
 	mz = page_cgroup_zoneinfo(pc);
 	/* huge page split is done under lru_lock. so, we have no races. */
 	MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page);
@@ -1031,14 +1026,10 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page)
 		return NULL;
 
 	pc = lookup_page_cgroup(page);
-	/*
-	 * Used bit is set without atomic ops but after smp_wmb().
-	 * For making pc->mem_cgroup visible, insert smp_rmb() here.
-	 */
-	smp_rmb();
 	if (!PageCgroupUsed(pc))
 		return NULL;
-
+	/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
+	smp_rmb();
 	mz = page_cgroup_zoneinfo(pc);
 	if (!mz)
 		return NULL;