slab: use struct page for slab management

Now, there are a few field in struct slab, so we can overload these
over struct page. This will save some memory and reduce cache footprint.

After this change, slabp_cache and slab_size no longer related to
a struct slab, so rename them as freelist_cache and freelist_size.

These changes are just mechanical ones and there is no functional change.

Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Pekka Enberg <penberg@iki.fi>

2 files changed, 15 insertions, 10 deletions

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 959cb369b197..95bf0c5a7eb9 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -42,18 +42,22 @@ struct page {
         /* First double word block */
         unsigned long flags;            /* Atomic flags, some possibly
                                          * updated asynchronously */
-        struct address_space *mapping;  /* If low bit clear, points to
-                                         * inode address_space, or NULL.
-                                         * If page mapped as anonymous
-                                         * memory, low bit is set, and
-                                         * it points to anon_vma object:
-                                         * see PAGE_MAPPING_ANON below.
-                                         */
+        union {
+                struct address_space *mapping;  /* If low bit clear, points to
+                                                 * inode address_space, or NULL.
+                                                 * If page mapped as anonymous
+                                                 * memory, low bit is set, and
+                                                 * it points to anon_vma object:
+                                                 * see PAGE_MAPPING_ANON below.
+                                                 */
+                void *s_mem;                    /* slab first object */
+        };
+
         /* Second double word */
         struct {
                 union {
                         pgoff_t index;          /* Our offset within mapping. */
-                        void *freelist;         /* slub/slob first free object */
+                        void *freelist;         /* sl[aou]b first free object */
                         bool pfmemalloc;        /* If set by the page allocator,
                                                  * ALLOC_NO_WATERMARKS was set
                                                  * and the low watermark was not
@@ -109,6 +113,7 @@ struct page {
                                 };
                                 atomic_t _count;                /* Usage count, see below. */
                         };
+                        unsigned int active;    /* SLAB */
                 };
         };
 
diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index cd401580bdd3..ca82e8ff89fa 100644
--- a/include/linux/slab_def.h
+++ b/include/linux/slab_def.h
@@ -41,8 +41,8 @@ struct kmem_cache {
 
         size_t colour;                  /* cache colouring range */
         unsigned int colour_off;        /* colour offset */
-        struct kmem_cache *slabp_cache;
-        unsigned int slab_size;
+        struct kmem_cache *freelist_cache;
+        unsigned int freelist_size;
 
         /* constructor func */
         void (*ctor)(void *obj);