[PATCH v2 2/3] mm: memcontrol: fix memcg id ref counter on swap charge move

Vladimir Davydov
2016-08-02T17:41:25Z

Since commit 73f576c04b941 swap entries do not pin memcg->css.refcnt
directly. Instead, they pin memcg->id.ref. So we should adjust the
reference counters accordingly when moving swap charges between cgroups.

Fixes: 73f576c04b941 ("mm: memcontrol: fix cgroup creation failure after many small jobs")
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org> [3.19+]
---
mm/memcontrol.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4ae12effe347..67109d556a4a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4031,9 +4031,9 @@ static struct cftype mem_cgroup_legacy_files[] = {

static DEFINE_IDR(mem_cgroup_idr);

-static void mem_cgroup_id_get(struct mem_cgroup *memcg)
+static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
{
- atomic_inc(&memcg->id.ref);
+ atomic_add(n, &memcg->id.ref);
}

static struct mem_cgroup *mem_cgroup_id_get_active(struct mem_cgroup *memcg)
@@ -4054,9 +4054,9 @@ static struct mem_cgroup *mem_cgroup_id_get_active(struct mem_cgroup *memcg)
return memcg;
}

-static void mem_cgroup_id_put(struct mem_cgroup *memcg)
+static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n)
{
- if (atomic_dec_and_test(&memcg->id.ref)) {
+ if (atomic_sub_and_test(n, &memcg->id.ref)) {
idr_remove(&mem_cgroup_idr, memcg->id.id);
memcg->id.id = 0;

@@ -4065,6 +4065,16 @@ static void mem_cgroup_id_put(struct mem_cgroup *memcg)
}
}

+static inline void mem_cgroup_id_get(struct mem_cgroup *memcg)
+{
+ mem_cgroup_id_get_many(memcg, 1);
+}
+
+static inline void mem_cgroup_id_put(struct mem_cgroup *memcg)
+{
+ mem_cgroup_id_put_many(memcg, 1);
+}
+
/**
* mem_cgroup_from_id - look up a memcg from a memcg id
* @id: the memcg id to look up
@@ -4699,6 +4709,8 @@ static void __mem_cgroup_clear_mc(void)
if (!mem_cgroup_is_root(mc.from))
page_counter_uncharge(&mc.from->memsw, mc.moved_swap);

+ mem_cgroup_id_put_many(mc.from, mc.moved_swap);
+
/*
* we charged both to->memory and to->memsw, so we
* should uncharge to->memory.
@@ -4706,9 +4718,9 @@ static void __mem_cgroup_clear_mc(void)
if (!mem_cgroup_is_root(mc.to))
page_counter_uncharge(&mc.to->memory, mc.moved_swap);

- css_put_many(&mc.from->css, mc.moved_swap);
+ mem_cgroup_id_get_many(mc.to, mc.moved_swap);
+ css_put_many(&mc.to->css, mc.moved_swap);

- /* we've already done css_get(mc.to) */
mc.moved_swap = 0;
}
memcg_oom_recover(from);
--
2.1.4