We are able to match a cache allocation to a particular memcg.  If the
task doesn't change groups during the allocation itself - a rare event,
this will give us a good picture about who is the first group to touch a
cache page.

This patch uses the now available infrastructure by calling
memcg_kmem_get_cache() before all the cache allocations.

Signed-off-by: Glauber Costa <redacted>
CC: Christoph Lameter <redacted>
CC: Pekka Enberg <penberg-bbCR+/B0CizivPeTLB3BmA@public.gmane.org>
CC: Michal Hocko <redacted>
CC: Kamezawa Hiroyuki <redacted>
CC: Johannes Weiner <redacted>
CC: Suleiman Souhlal <redacted>
---
 include/linux/slub_def.h |   18 +++++++++++++-----
 mm/memcontrol.c          |    2 ++
 mm/slab.c                |    4 ++++
 mm/slub.c                |    1 +
 4 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 8bb8ad2..148000a 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h

@@ -13,6 +13,8 @@
 #include <linux/kobject.h>
 
 #include <linux/kmemleak.h>
+#include <linux/memcontrol.h>
+#include <linux/mm.h>
 
 enum stat_item {
 	ALLOC_FASTPATH,		/* Allocation from cpu slab */

@@ -209,14 +211,14 @@ static __always_inline int kmalloc_index(size_t size)
  * This ought to end up with a global pointer to the right cache
  * in kmalloc_caches.
  */
-static __always_inline struct kmem_cache *kmalloc_slab(size_t size)
+static __always_inline struct kmem_cache *kmalloc_slab(gfp_t flags, size_t size)
 {
 	int index = kmalloc_index(size);
 
 	if (index == 0)
 		return NULL;
 
-	return kmalloc_caches[index];
+	return memcg_kmem_get_cache(kmalloc_caches[index], flags);
 }
 
 void *kmem_cache_alloc(struct kmem_cache *, gfp_t);

@@ -225,7 +227,13 @@ void *__kmalloc(size_t size, gfp_t flags);
 static __always_inline void *
 kmalloc_order(size_t size, gfp_t flags, unsigned int order)
 {
-	void *ret = (void *) __get_free_pages(flags | __GFP_COMP, order);
+	void *ret;
+
+	flags = __GFP_COMP;
+#ifdef CONFIG_MEMCG_KMEM
+	flags |= __GFP_KMEMCG;
+#endif