[PATCH -mm 1/8] memcg: add pointer from memcg_cache_params to owner cache

Vladimir Davydov
2014-07-07T12:00:29Z

We don't keep a pointer to the owner kmem cache in the
memcg_cache_params struct, because we can always get the cache by
reading the slot corresponding to the owner memcg in the root cache's
memcg_caches array (see memcg_params_to_cache). However, this won't work
when kmem cache re-parenting is introduced, because the slot in the root
cache's arrays must be cleared on css offline then.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
---
include/linux/slab.h | 2 ++
mm/memcontrol.c | 25 +++++--------------------
2 files changed, 7 insertions(+), 20 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 68b1feaba9d6..8bc62d5ef903 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -523,6 +523,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
*
* Child caches will hold extra metadata needed for its operation. Fields are:
*
+ * @cachep: cache which this struct is for
* @memcg: pointer to the memcg this cache belongs to
* @list: list_head for the list of all caches in this memcg
* @root_cache: pointer to the global, root cache, this cache was derived from
@@ -536,6 +537,7 @@ struct memcg_cache_params {
union {
struct kmem_cache *memcg_caches[0];
struct {
+ struct kmem_cache *cachep;
struct mem_cgroup *memcg;
struct list_head list;
struct kmem_cache *root_cache;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d1b311687769..98b43a8125b9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2781,19 +2781,6 @@ static inline bool memcg_can_account_kmem(struct mem_cgroup *memcg)
memcg_kmem_is_active(memcg);
}

-/*
- * This is a bit cumbersome, but it is rarely used and avoids a backpointer
- * in the memcg_cache_params struct.
- */
-static struct kmem_cache *memcg_params_to_cache(struct memcg_cache_params *p)
-{
- struct kmem_cache *cachep;
-
- VM_BUG_ON(p->is_root_cache);
- cachep = p->root_cache;
- return cache_from_memcg_idx(cachep, memcg_cache_id(p->memcg));
-}
-
#ifdef CONFIG_SLABINFO
static int mem_cgroup_slabinfo_read(struct seq_file *m, void *v)
{
@@ -2807,7 +2794,7 @@ static int mem_cgroup_slabinfo_read(struct seq_file *m, void *v)

mutex_lock(&memcg_slab_mutex);
list_for_each_entry(params, &memcg->memcg_slab_caches, list)
- cache_show(memcg_params_to_cache(params), m);
+ cache_show(params->cachep, m);
mutex_unlock(&memcg_slab_mutex);

return 0;
@@ -2982,6 +2969,7 @@ int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
return -ENOMEM;

if (memcg) {
+ s->memcg_params->cachep = s;
s->memcg_params->memcg = memcg;
s->memcg_params->root_cache = root_cache;
atomic_long_set(&s->memcg_params->refcnt, 1);
@@ -3072,10 +3060,9 @@ static void memcg_unregister_cache_func(struct work_struct *work)
{
struct memcg_cache_params *params =
container_of(work, struct memcg_cache_params, unregister_work);
- struct kmem_cache *cachep = memcg_params_to_cache(params);

mutex_lock(&memcg_slab_mutex);
- memcg_unregister_cache(cachep);
+ memcg_unregister_cache(params->cachep);
mutex_unlock(&memcg_slab_mutex);
}

@@ -3140,7 +3127,6 @@ int __memcg_cleanup_cache_params(struct kmem_cache *s)

static void memcg_unregister_all_caches(struct mem_cgroup *memcg)
{
- struct kmem_cache *cachep;
struct memcg_cache_params *params, *tmp;
LIST_HEAD(empty_caches);

@@ -3149,7 +3135,7 @@ static void memcg_unregister_all_caches(struct mem_cgroup *memcg)

mutex_lock(&memcg_slab_mutex);
list_for_each_entry_safe(params, tmp, &memcg->memcg_slab_caches, list) {
- cachep = memcg_params_to_cache(params);
+ struct kmem_cache *cachep = params->cachep;

memcg_cache_mark_dead(cachep);
kmem_cache_shrink(cachep);
@@ -3173,8 +3159,7 @@ static void memcg_unregister_all_caches(struct mem_cgroup *memcg)
while (!list_empty(&empty_caches)) {
params = list_first_entry(&empty_caches,
struct memcg_cache_params, list);
- cachep = memcg_params_to_cache(params);
- memcg_unregister_cache(cachep);
+ memcg_unregister_cache(params->cachep);
}
mutex_unlock(&memcg_slab_mutex);
}
--
1.7.10.4