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>

---
 include/linux/mm.h       |    4 ----
 include/linux/mm_types.h |    9 ++-------
 mm/slub.c                |    2 --
 3 files changed, 2 insertions(+), 13 deletions(-)

Index: linux-2.6.23-rc1/include/linux/mm.h
===================================================================
--- linux-2.6.23-rc1.orig/include/linux/mm.h	2007-07-27 21:34:36.000000000 -0700
+++ linux-2.6.23-rc1/include/linux/mm.h	2007-07-27 21:35:54.000000000 -0700
@@ -630,10 +630,6 @@ static inline struct address_space *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;
Index: linux-2.6.23-rc1/include/linux/mm_types.h
===================================================================
--- linux-2.6.23-rc1.orig/include/linux/mm_types.h	2007-07-27 21:34:36.000000000 -0700
+++ linux-2.6.23-rc1/include/linux/mm_types.h	2007-07-27 21:35:54.000000000 -0700
@@ -49,13 +49,8 @@ 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. */
Index: linux-2.6.23-rc1/mm/slub.c
===================================================================
--- linux-2.6.23-rc1.orig/mm/slub.c	2007-07-27 21:35:43.000000000 -0700
+++ linux-2.6.23-rc1/mm/slub.c	2007-07-27 21:35:54.000000000 -0700
@@ -1115,7 +1115,6 @@ static struct page *new_slab(struct kmem
 	set_freepointer(s, last, NULL);
 
 	page->freelist = start;
-	page->lockless_freelist = NULL;
 	page->inuse = 0;
 out:
 	if (flags & __GFP_WAIT)
@@ -1140,7 +1139,6 @@ static void __free_slab(struct kmem_cach
 		NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
 		- pages);
 
-	page->mapping = NULL;
 	__free_pages(page, s->order);
 }