[Devel] [PATCH 2/8] memcg, slab: remove cgroup name from memcg cache names

[Vladimir Davydov]

The cgroup name is not informative at all in case the cgroup hierarchy
is not flat. Besides, we can always find the memcg a particular cache
belongs to by its kmemcg id, which is now exported via "memory.kmem.id"
cgroup fs file for each memcg.

So let's remove the cgroup name part from kmem caches names - it will
greatly simplify the call paths and make the code look clearer.

Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
---
 mm/memcontrol.c  |   63 +++++++++++++-----------------------------------------
 mm/slab_common.c |    6 +++++-
 2 files changed, 20 insertions(+), 49 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 91d242707404..3351c5b5486d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3405,44 +3405,6 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
 	schedule_work(&cachep->memcg_params->destroy);
 }
 
-static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
-						  struct kmem_cache *s)
-{
-	struct kmem_cache *new = NULL;
-	static char *tmp_name = NULL;
-	static DEFINE_MUTEX(mutex);	/* protects tmp_name */
-
-	BUG_ON(!memcg_can_account_kmem(memcg));
-
-	mutex_lock(&mutex);
-	/*
-	 * kmem_cache_create_memcg duplicates the given name and
-	 * cgroup_name for this name requires RCU context.
-	 * This static temporary buffer is used to prevent from
-	 * pointless shortliving allocation.
-	 */
-	if (!tmp_name) {
-		tmp_name = kmalloc(PATH_MAX, GFP_KERNEL);
-		if (!tmp_name)
-			goto out;
-	}
-
-	rcu_read_lock();
-	snprintf(tmp_name, PATH_MAX, "%s(%d:%s)", s->name,
-			 memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup));
-	rcu_read_unlock();
-
-	new = kmem_cache_create_memcg(memcg, tmp_name, s->object_size, s->align,
-				      (s->flags & ~SLAB_PANIC), s->ctor, s);
-	if (new)
-		new->allocflags |= __GFP_KMEMCG;
-	else
-		new = s;
-out:
-	mutex_unlock(&mutex);
-	return new;
-}
-
 void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 {
 	struct kmem_cache *c;
@@ -3489,12 +3451,6 @@ void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 	mutex_unlock(&activate_kmem_mutex);
 }
 
-struct create_work {
-	struct mem_cgroup *memcg;
-	struct kmem_cache *cachep;
-	struct work_struct work;
-};
-
 static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
 {
 	struct kmem_cache *cachep;
@@ -3512,13 +3468,24 @@ static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
 	mutex_unlock(&memcg->slab_caches_mutex);
 }
 
+struct create_work {
+	struct mem_cgroup *memcg;
+	struct kmem_cache *cachep;
+	struct work_struct work;
+};
+
 static void memcg_create_cache_work_func(struct work_struct *w)
 {
-	struct create_work *cw;
+	struct create_work *cw = container_of(w, struct create_work, work);
+	struct mem_cgroup *memcg = cw->memcg;
+	struct kmem_cache *s = cw->cachep;
+	struct kmem_cache *new;
 
-	cw = container_of(w, struct create_work, work);
-	memcg_create_kmem_cache(cw->memcg, cw->cachep);
-	css_put(&cw->memcg->css);
+	new = kmem_cache_create_memcg(memcg, s->name, s->object_size, s->align,
+				      (s->flags & ~SLAB_PANIC), s->ctor, s);
+	if (new)
+		new->allocflags |= __GFP_KMEMCG;
+	css_put(&memcg->css);
 	kfree(cw);
 }
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 1ec3c619ba04..152d9b118b7a 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -213,7 +213,11 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
 	s->align = calculate_alignment(flags, align, size);
 	s->ctor = ctor;
 
-	s->name = kstrdup(name, GFP_KERNEL);
+	if (!memcg)
+		s->name = kstrdup(name, GFP_KERNEL);
+	else
+		s->name = kasprintf(GFP_KERNEL, "%s:%d",
+				    name, memcg_cache_id(memcg));
 	if (!s->name)
 		goto out_free_cache;
 
-- 
1.7.10.4