SLUB: Do not use page->mapping

After moving the lockless_freelist to kmem_cache_cpu we no longer need
page->lockless_freelist. Restructure the use of the struct page fields in
such a way that we never touch the mapping field.

This is turn allows us to remove the special casing of SLUB when determining
the mapping of a page (needed for corner cases of virtual caches machines that
need to flush caches of processors mapping a page).

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 2 insertions, 13 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6a68d41444f8..292c68623759 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -568,10 +568,6 @@ static inline struct address_space *page_mapping(struct page *page)
         VM_BUG_ON(PageSlab(page));
         if (unlikely(PageSwapCache(page)))
                 mapping = &swapper_space;
-#ifdef CONFIG_SLUB
-        else if (unlikely(PageSlab(page)))
-                mapping = NULL;
-#endif
         else if (unlikely((unsigned long)mapping & PAGE_MAPPING_ANON))
                 mapping = NULL;
         return mapping;
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 145b3d053048..0cdc8fbf6431 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -62,13 +62,8 @@ struct page {
 #if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
             spinlock_t ptl;
 #endif
-            struct {                    /* SLUB uses */
-                void **lockless_freelist;
-                struct kmem_cache *slab;        /* Pointer to slab */
-            };
-            struct {
-                struct page *first_page;        /* Compound pages */
-            };
+            struct kmem_cache *slab;    /* SLUB: Pointer to slab */
+            struct page *first_page;    /* Compound tail pages */
         };
         union {
                 pgoff_t index;          /* Our offset within mapping. */
diff --git a/mm/slub.c b/mm/slub.c
index 4b8037f14fce..aa8bb072651b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1127,7 +1127,6 @@ static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
         set_freepointer(s, last, NULL);
 
         page->freelist = start;
-        page->lockless_freelist = NULL;
         page->inuse = 0;
 out:
         if (flags & __GFP_WAIT)
@@ -1153,7 +1152,6 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
                 NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
                 - pages);
 
-        page->mapping = NULL;
         __free_pages(page, s->order);
 }