1 files changed, 24 insertions, 0 deletions

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 743a10415122..00efba149222 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -177,6 +177,30 @@ void kmem_cache_free(struct kmem_cache *, void *);
 #endif
 
 /*
+ * This is the main placeholder for memcg-related information in kmem caches.
+ * struct kmem_cache will hold a pointer to it, so the memory cost while
+ * disabled is 1 pointer. The runtime cost while enabled, gets bigger than it
+ * would otherwise be if that would be bundled in kmem_cache: we'll need an
+ * extra pointer chase. But the trade off clearly lays in favor of not
+ * penalizing non-users.
+ *
+ * Both the root cache and the child caches will have it. For the root cache,
+ * this will hold a dynamically allocated array large enough to hold
+ * information about the currently limited memcgs in the system.
+ *
+ * Child caches will hold extra metadata needed for its operation. Fields are:
+ *
+ * @memcg: pointer to the memcg this cache belongs to
+ */
+struct memcg_cache_params {
+        bool is_root_cache;
+        union {
+                struct kmem_cache *memcg_caches[0];
+                struct mem_cgroup *memcg;
+        };
+};
+
+/*
  * Common kmalloc functions provided by all allocators
  */
 void * __must_check __krealloc(const void *, size_t, gfp_t);