path: root/mm
diff options
authorDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>2009-01-29 14:25:11 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-29 18:04:43 -0800
commit7bcc1bb1232de6efc0b85e0c7fe38e90b2436318 (patch)
tree3952a706885f4c57217f4196f055a7c16d0af80b /mm
parentbaef99a08a2e23d9386b47e53fa5f0d44fc98f66 (diff)
memcg: get/put parents at create/free
The lifetime of struct cgroup and struct mem_cgroup is different and mem_cgroup has its own reference count for handling references from swap_cgroup. This causes strange problem that the parent mem_cgroup dies while child mem_cgroup alive, and this problem causes a bug in case of use_hierarchy==1 because res_counter_uncharge climbs up the tree. This patch is for avoiding it by getting the parent at create, and putting it at freeing. Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Reviewed-by; KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Paul Menage <menage@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 22 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4d0ea3ceba6..76feccd26dc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -202,6 +202,7 @@ pcg_default_flags[NR_CHARGE_TYPE] = {
static void mem_cgroup_get(struct mem_cgroup *mem);
static void mem_cgroup_put(struct mem_cgroup *mem);
+static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
struct page_cgroup *pc,
@@ -2193,10 +2194,23 @@ static void mem_cgroup_get(struct mem_cgroup *mem)
static void mem_cgroup_put(struct mem_cgroup *mem)
- if (atomic_dec_and_test(&mem->refcnt))
+ if (atomic_dec_and_test(&mem->refcnt)) {
+ struct mem_cgroup *parent = parent_mem_cgroup(mem);
+ if (parent)
+ mem_cgroup_put(parent);
+ }
+ * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
+ */
+static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem)
+ if (!mem->res.parent)
+ return NULL;
+ return mem_cgroup_from_res_counter(mem->res.parent, res);
static void __init enable_swap_cgroup(void)
@@ -2235,6 +2249,13 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
if (parent && parent->use_hierarchy) {
res_counter_init(&mem->res, &parent->res);
res_counter_init(&mem->memsw, &parent->memsw);
+ /*
+ * We increment refcnt of the parent to ensure that we can
+ * safely access it on res_counter_charge/uncharge.
+ * This refcnt will be decremented when freeing this
+ * mem_cgroup(see mem_cgroup_put).
+ */
+ mem_cgroup_get(parent);
} else {
res_counter_init(&mem->res, NULL);
res_counter_init(&mem->memsw, NULL);