slab: Use page struct fields instead of casting

Add fields to the page struct so that it is properly documented that
slab overlays the lru fields.

This cleans up some casts in slab.

Reviewed-by: Glauber Costa <glommer@parallels.com>
Reviewed-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5922c345259272fac8db30b6f1bf4905301012b5..680a5e4e8cd50b2db17cc8b7c42f189e4747abcb 100644 (file)
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -110,6 +110,10 @@ struct page {
                };
 
                struct list_head list;  /* slobs list of pages */
+               struct {                /* slab fields */
+                       struct kmem_cache *slab_cache;
+                       struct slab *slab_page;
+               };
        };
 
        /* Remainder is not double word aligned */

diff --git a/mm/slab.c b/mm/slab.c
index e901a36e2520c2b7aa5123ddcd0553415b764397..af05147d7abde6593192d472f54acd1db03719ec 100644 (file)
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -496,25 +496,25 @@ static bool slab_max_order_set __initdata;
  */
 static inline void page_set_cache(struct page *page, struct kmem_cache *cache)
 {
-       page->lru.next = (struct list_head *)cache;
+       page->slab_cache = cache;
 }
 
 static inline struct kmem_cache *page_get_cache(struct page *page)
 {
        page = compound_head(page);
        BUG_ON(!PageSlab(page));
-       return (struct kmem_cache *)page->lru.next;
+       return page->slab_cache;
 }
 
 static inline void page_set_slab(struct page *page, struct slab *slab)
 {
-       page->lru.prev = (struct list_head *)slab;
+       page->slab_page = slab;
 }
 
 static inline struct slab *page_get_slab(struct page *page)
 {
        BUG_ON(!PageSlab(page));
-       return (struct slab *)page->lru.prev;
+       return page->slab_page;
 }
 
 static inline struct kmem_cache *virt_to_cache(const void *obj)