SLUB: Introduce and use SLUB_MAX_SIZE and SLUB_PAGE_SHIFT constants

As a preparational patch to bump up page allocator pass-through threshold,
introduce two new constants SLUB_MAX_SIZE and SLUB_PAGE_SHIFT and convert
mm/slub.c to use them.

Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Tested-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
diff --git a/mm/slub.c b/mm/slub.c
index bdc9abb..5a5e7f5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2475,7 +2475,7 @@
  *		Kmalloc subsystem
  *******************************************************************/
 
-struct kmem_cache kmalloc_caches[PAGE_SHIFT + 1] __cacheline_aligned;
+struct kmem_cache kmalloc_caches[SLUB_PAGE_SHIFT] __cacheline_aligned;
 EXPORT_SYMBOL(kmalloc_caches);
 
 static int __init setup_slub_min_order(char *str)
@@ -2537,7 +2537,7 @@
 }
 
 #ifdef CONFIG_ZONE_DMA
-static struct kmem_cache *kmalloc_caches_dma[PAGE_SHIFT + 1];
+static struct kmem_cache *kmalloc_caches_dma[SLUB_PAGE_SHIFT];
 
 static void sysfs_add_func(struct work_struct *w)
 {
@@ -2658,7 +2658,7 @@
 {
 	struct kmem_cache *s;
 
-	if (unlikely(size > PAGE_SIZE))
+	if (unlikely(size > SLUB_MAX_SIZE))
 		return kmalloc_large(size, flags);
 
 	s = get_slab(size, flags);
@@ -2686,7 +2686,7 @@
 {
 	struct kmem_cache *s;
 
-	if (unlikely(size > PAGE_SIZE))
+	if (unlikely(size > SLUB_MAX_SIZE))
 		return kmalloc_large_node(size, flags, node);
 
 	s = get_slab(size, flags);
@@ -2985,7 +2985,7 @@
 		caches++;
 	}
 
-	for (i = KMALLOC_SHIFT_LOW; i <= PAGE_SHIFT; i++) {
+	for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
 		create_kmalloc_cache(&kmalloc_caches[i],
 			"kmalloc", 1 << i, GFP_KERNEL);
 		caches++;
@@ -3022,7 +3022,7 @@
 	slab_state = UP;
 
 	/* Provide the correct kmalloc names now that the caches are up */
-	for (i = KMALLOC_SHIFT_LOW; i <= PAGE_SHIFT; i++)
+	for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++)
 		kmalloc_caches[i]. name =
 			kasprintf(GFP_KERNEL, "kmalloc-%d", 1 << i);
 
@@ -3222,7 +3222,7 @@
 {
 	struct kmem_cache *s;
 
-	if (unlikely(size > PAGE_SIZE))
+	if (unlikely(size > SLUB_MAX_SIZE))
 		return kmalloc_large(size, gfpflags);
 
 	s = get_slab(size, gfpflags);
@@ -3238,7 +3238,7 @@
 {
 	struct kmem_cache *s;
 
-	if (unlikely(size > PAGE_SIZE))
+	if (unlikely(size > SLUB_MAX_SIZE))
 		return kmalloc_large_node(size, gfpflags, node);
 
 	s = get_slab(size, gfpflags);