sl[au]b: charge slabs to kmemcg explicitly

We have only a few places where we actually want to charge kmem so
instead of intruding into the general page allocation path with
__GFP_KMEMCG it's better to explictly charge kmem there.  All kmem
charges will be easier to follow that way.

This is a step towards removing __GFP_KMEMCG.  It removes __GFP_KMEMCG
from memcg caches' allocflags.  Instead it makes slab allocation path
call memcg_charge_kmem directly getting memcg to charge from the cache's
memcg params.

This also eliminates any possibility of misaccounting an allocation
going from one memcg's cache to another memcg, because now we always
charge slabs against the memcg the cache belongs to.  That's why this
patch removes the big comment to memcg_kmem_get_cache.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 7 deletions

diff --git a/mm/slub.c b/mm/slub.c
index d05a5483106d..fc9831851be6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1312,17 +1312,26 @@ static inline void slab_free_hook(struct kmem_cache *s, void *x)
 /*
  * Slab allocation and freeing
  */
-static inline struct page *alloc_slab_page(gfp_t flags, int node,
-					struct kmem_cache_order_objects oo)
+static inline struct page *alloc_slab_page(struct kmem_cache *s,
+		gfp_t flags, int node, struct kmem_cache_order_objects oo)
 {
+	struct page *page;
 	int order = oo_order(oo);
 
 	flags |= __GFP_NOTRACK;
 
+	if (memcg_charge_slab(s, flags, order))
+		return NULL;
+
 	if (node == NUMA_NO_NODE)
-		return alloc_pages(flags, order);
+		page = alloc_pages(flags, order);
 	else
-		return alloc_pages_exact_node(node, flags, order);
+		page = alloc_pages_exact_node(node, flags, order);
+
+	if (!page)
+		memcg_uncharge_slab(s, order);
+
+	return page;
 }
 
 static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
@@ -1344,7 +1353,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	 */
 	alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;
 
-	page = alloc_slab_page(alloc_gfp, node, oo);
+	page = alloc_slab_page(s, alloc_gfp, node, oo);
 	if (unlikely(!page)) {
 		oo = s->min;
 		alloc_gfp = flags;
@@ -1352,7 +1361,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 		 * Allocation may have failed due to fragmentation.
 		 * Try a lower order alloc if possible
 		 */
-		page = alloc_slab_page(alloc_gfp, node, oo);
+		page = alloc_slab_page(s, alloc_gfp, node, oo);
 
 		if (page)
 			stat(s, ORDER_FALLBACK);
@@ -1468,7 +1477,8 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
 	page_mapcount_reset(page);
 	if (current->reclaim_state)
 		current->reclaim_state->reclaimed_slab += pages;
-	__free_memcg_kmem_pages(page, order);
+	__free_pages(page, order);
+	memcg_uncharge_slab(s, order);
 }
 
 #define need_reserve_slab_rcu						\