slab common: add functions for kmem_cache_node access

The patchset provides two new functions in mm/slab.h and modifies SLAB
and SLUB to use these.  The kmem_cache_node structure is shared between
both allocators and the use of common accessors will allow us to move
more code into slab_common.c in the future.

This patch (of 3):

These functions allow to eliminate repeatedly used code in both SLAB and
SLUB and also allow for the insertion of debugging code that may be
needed in the development process.

Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slab.h

@@ -262,7 +262,7 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
 }
 #endif
 
-
+#ifndef CONFIG_SLOB
 /*
  * The slab lists for all objects.
  */
@@ -294,5 +294,20 @@ struct kmem_cache_node {
 
 };
 
+static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
+{
+	return s->node[node];
+}
+
+/*
+ * Iterator over all nodes. The body will be executed for each node that has
+ * a kmem_cache_node structure allocated (which is true for all online nodes)
+ */
+#define for_each_kmem_cache_node(__s, __node, __n) \
+	for (__node = 0; __n = get_node(__s, __node), __node < nr_node_ids; __node++) \
+		 if (__n)
+
+#endif
+
 void *slab_next(struct seq_file *m, void *p, loff_t *pos);
 void slab_stop(struct seq_file *m, void *p);

mm/slub.c

@@ -233,11 +233,6 @@ static inline void stat(const struct kmem_cache *s, enum stat_item si)
  * 			Core slab cache functions
  *******************************************************************/
 
-static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
-{
-	return s->node[node];
-}
-
 /* Verify that a pointer has an address that is valid within a slab page */
 static inline int check_valid_pointer(struct kmem_cache *s,
 				struct page *page, const void *object)