Switching to an indirect scheme of getting mem_cgroup pointer for
!root slab pages broke /proc/kpagecgroup interface for them.
Let's fix it by learning page_cgroup_ino() how to get memcg
pointer for slab pages.
Reported-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Signed-off-by: Roman Gushchin <guro@xxxxxx>
---
mm/memcontrol.c | 5 ++++-
mm/slab.h | 21 +++++++++++++++++++++
mm/slab_common.c | 1 +
3 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6e4d9ed16069..8114838759f6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -494,7 +494,10 @@ ino_t page_cgroup_ino(struct page *page)
unsigned long ino = 0;
rcu_read_lock();
- memcg = READ_ONCE(page->mem_cgroup);
+ if (PageSlab(page))
+ memcg = memcg_from_slab_page(page);
+ else
+ memcg = READ_ONCE(page->mem_cgroup);
while (memcg && !(memcg->css.flags & CSS_ONLINE))
memcg = parent_mem_cgroup(memcg);
if (memcg)
diff --git a/mm/slab.h b/mm/slab.h
index acdc1810639d..cb684fbe2cc2 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -256,6 +256,22 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
return s->memcg_params.root_cache;
}
+static inline struct mem_cgroup *memcg_from_slab_page(struct page *page)
+{
+ struct kmem_cache *s;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
+ if (PageTail(page))
+ page = compound_head(page);
+
+ s = READ_ONCE(page->slab_cache);
+ if (s && !is_root_cache(s))
+ return rcu_dereference(s->memcg_params.memcg);
+
+ return NULL;
+}
+
static __always_inline int memcg_charge_slab(struct page *page,
gfp_t gfp, int order,
struct kmem_cache *s)
@@ -338,6 +354,11 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
return s;
}
+static inline struct mem_cgroup *memcg_from_slab_page(struct page *page)
+{
+ return NULL;
+}
+
static inline int memcg_charge_slab(struct page *page, gfp_t gfp, int order,
struct kmem_cache *s)
{
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 36673a43ed31..0cfdad0a0aac 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -253,6 +253,7 @@ static void memcg_unlink_cache(struct kmem_cache *s)
list_del(&s->memcg_params.kmem_caches_node);
mem_cgroup_put(rcu_dereference_protected(s->memcg_params.memcg,
lockdep_is_held(&slab_mutex)));
+ rcu_assign_pointer(s->memcg_params.memcg, NULL);
}
}
#else
--
2.20.1
