[PATCH v2 16/29] slub: create duplicate cache

[Glauber Costa]

This patch provides kmem_cache_dup(), that duplicates
a cache for a memcg, preserving its creation properties.
Object size, alignment and flags are all respected.

When a duplicate cache is created, the parent cache cannot
be destructed during the child lifetime. To assure this,
its reference count is increased if the cache creation
succeeds.

Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxx>
CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
CC: Michal Hocko <mhocko@xxxxxxx>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: Johannes Weiner <hannes@xxxxxxxxxxx>
CC: Suleiman Souhlal <suleiman@xxxxxxxxxx>
---
 include/linux/memcontrol.h |    2 ++
 include/linux/slab.h       |    2 ++
 mm/memcontrol.c            |   17 +++++++++++++++++
 mm/slub.c                  |   31 +++++++++++++++++++++++++++++++
 4 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 99e14b9..f93021a 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -445,6 +445,8 @@ int memcg_css_id(struct mem_cgroup *memcg);
 void mem_cgroup_register_cache(struct mem_cgroup *memcg,
 				      struct kmem_cache *s);
 void mem_cgroup_release_cache(struct kmem_cache *cachep);
+extern char *mem_cgroup_cache_name(struct mem_cgroup *memcg,
+				   struct kmem_cache *cachep);
 #else
 static inline void mem_cgroup_register_cache(struct mem_cgroup *memcg,
 					     struct kmem_cache *s)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 1386650..e73ef71 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -322,6 +322,8 @@ extern void *__kmalloc_track_caller(size_t, gfp_t, unsigned long);
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
 #define MAX_KMEM_CACHE_TYPES 400
+extern struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg,
+					 struct kmem_cache *cachep);
 #else
 #define MAX_KMEM_CACHE_TYPES 0
 #endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9327996..a8171cb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -467,6 +467,23 @@ struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
 EXPORT_SYMBOL(tcp_proto_cgroup);
 #endif /* CONFIG_INET */
 
+char *mem_cgroup_cache_name(struct mem_cgroup *memcg, struct kmem_cache *cachep)
+{
+	char *name;
+	struct dentry *dentry;
+
+	rcu_read_lock();
+	dentry = rcu_dereference(memcg->css.cgroup->dentry);
+	rcu_read_unlock();
+
+	BUG_ON(dentry == NULL);
+
+	name = kasprintf(GFP_KERNEL, "%s(%d:%s)",
+	    cachep->name, css_id(&memcg->css), dentry->d_name.name);
+
+	return name;
+}
+
 struct ida cache_types;
 
 void mem_cgroup_register_cache(struct mem_cgroup *memcg,
diff --git a/mm/slub.c b/mm/slub.c
index 1698371..9b21b38 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4034,6 +4034,37 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
 }
 EXPORT_SYMBOL(kmem_cache_create);
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg,
+				  struct kmem_cache *s)
+{
+	char *name;
+	struct kmem_cache *new;
+
+	name = mem_cgroup_cache_name(memcg, s);
+	if (!name)
+		return NULL;
+
+	new = kmem_cache_create_memcg(memcg, name, s->objsize, s->align,
+				      (s->allocflags & ~SLAB_PANIC), s->ctor);
+
+	/*
+	 * We increase the reference counter in the parent cache, to
+	 * prevent it from being deleted. If kmem_cache_destroy() is
+	 * called for the root cache before we call it for a child cache,
+	 * it will be queued for destruction when we finally drop the
+	 * reference on the child cache.
+	 */
+	if (new) {
+		down_write(&slub_lock);
+		s->refcount++;
+		up_write(&slub_lock);
+	}
+	kfree(name);
+	return new;
+}
+#endif
+
 #ifdef CONFIG_SMP
 /*
  * Use the cpu notifier to insure that the cpu slabs are flushed when
-- 
1.7.7.6

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