From: Balbir Singh <balbir@linux.vnet.ibm.com>
Date: Thu, 7 Feb 2008 08:14:18 +0000 (-0800)
Subject: Memory controller use rcu_read_lock() in mem_cgroup_cache_charge()
X-Git-Tag: v2.6.25-rc1~452
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ac44d354d5c9ced49b1165d6496f134501134219;p=linux-2.6

Memory controller use rcu_read_lock() in mem_cgroup_cache_charge()

Hugh Dickins noticed that we were using rcu_dereference() without
rcu_read_lock() in the cache charging routine. The patch below fixes
this problem

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 975e89935d..160101a05b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -456,16 +456,20 @@ int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
 int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 				gfp_t gfp_mask)
 {
+	int ret = 0;
 	struct mem_cgroup *mem;
 	if (!mm)
 		mm = &init_mm;
 
+	rcu_read_lock();
 	mem = rcu_dereference(mm->mem_cgroup);
+	css_get(&mem->css);
+	rcu_read_unlock();
 	if (mem->control_type == MEM_CGROUP_TYPE_ALL)
-		return mem_cgroup_charge_common(page, mm, gfp_mask,
+		ret = mem_cgroup_charge_common(page, mm, gfp_mask,
 				MEM_CGROUP_CHARGE_TYPE_CACHE);
-	else
-		return 0;
+	css_put(&mem->css);
+	return ret;
 }
 
 /*