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 975e899..160101a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -456,16 +456,20 @@
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;
}
/*