From: Nick Piggin <npiggin@suse.de>

Now that compound page handling is properly fixed in the VM, move nommu
over to using compound pages rather than rolling their own refcounting.

nommu vm page refcounting is broken anyway, but there is no need to have
divergent code in the core VM now, nor when it gets fixed.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: David Howells <dhowells@redhat.com>

(Needs testing, please).
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 fs/ramfs/file-nommu.c |    3 +--
 include/linux/mm.h    |    4 ----
 mm/internal.h         |   12 ------------
 mm/nommu.c            |    4 ++--
 mm/page_alloc.c       |    7 -------
 mm/slab.c             |    9 ++++++++-
 6 files changed, 11 insertions(+), 28 deletions(-)

diff -puN fs/ramfs/file-nommu.c~mm-nommu-use-compound-pages fs/ramfs/file-nommu.c
--- devel/fs/ramfs/file-nommu.c~mm-nommu-use-compound-pages	2006-02-27 20:57:55.000000000 -0800
+++ devel-akpm/fs/ramfs/file-nommu.c	2006-02-27 20:57:55.000000000 -0800
@@ -87,8 +87,7 @@ static int ramfs_nommu_expand_for_mappin
 	xpages = 1UL << order;
 	npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 
-	for (loop = 0; loop < npages; loop++)
-		set_page_count(pages + loop, 1);
+	split_page(pages, order);
 
 	/* trim off any pages we don't actually require */
 	for (loop = npages; loop < xpages; loop++)
diff -puN include/linux/mm.h~mm-nommu-use-compound-pages include/linux/mm.h
--- devel/include/linux/mm.h~mm-nommu-use-compound-pages	2006-02-27 20:57:55.000000000 -0800
+++ devel-akpm/include/linux/mm.h	2006-02-27 20:57:55.000000000 -0800
@@ -327,11 +327,7 @@ static inline void get_page(struct page 
 
 void put_page(struct page *page);
 
-#ifdef CONFIG_MMU
 void split_page(struct page *page, unsigned int order);
-#else
-static inline void split_page(struct page *page, unsigned int order) {}
-#endif
 
 /*
  * Multiple processes may "see" the same page. E.g. for untouched
diff -puN mm/internal.h~mm-nommu-use-compound-pages mm/internal.h
--- devel/mm/internal.h~mm-nommu-use-compound-pages	2006-02-27 20:57:55.000000000 -0800
+++ devel-akpm/mm/internal.h	2006-02-27 20:57:55.000000000 -0800
@@ -15,19 +15,7 @@
 
 static inline void set_page_refs(struct page *page, int order)
 {
-#ifdef CONFIG_MMU
 	set_page_count(page, 1);
-#else
-	int i;
-
-	/*
-	 * We need to reference all the pages for this order, otherwise if
-	 * anyone accesses one of the pages with (get/put) it will be freed.
-	 * - eg: access_process_vm()
-	 */
-	for (i = 0; i < (1 << order); i++)
-		set_page_count(page + i, 1);
-#endif /* CONFIG_MMU */
 }
 
 static inline void __put_page(struct page *page)
diff -puN mm/nommu.c~mm-nommu-use-compound-pages mm/nommu.c
--- devel/mm/nommu.c~mm-nommu-use-compound-pages	2006-02-27 20:57:55.000000000 -0800
+++ devel-akpm/mm/nommu.c	2006-02-27 20:57:55.000000000 -0800
@@ -159,7 +159,7 @@ void *__vmalloc(unsigned long size, gfp_
 	/*
 	 * kmalloc doesn't like __GFP_HIGHMEM for some reason
 	 */
-	return kmalloc(size, gfp_mask & ~__GFP_HIGHMEM);
+	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
 }
 
 struct page * vmalloc_to_page(void *addr)
@@ -623,7 +623,7 @@ static int do_mmap_private(struct vm_are
 	 * - note that this may not return a page-aligned address if the object
 	 *   we're allocating is smaller than a page
 	 */
-	base = kmalloc(len, GFP_KERNEL);
+	base = kmalloc(len, GFP_KERNEL|__GFP_COMP);
 	if (!base)
 		goto enomem;
 
diff -puN mm/page_alloc.c~mm-nommu-use-compound-pages mm/page_alloc.c
--- devel/mm/page_alloc.c~mm-nommu-use-compound-pages	2006-02-27 20:57:55.000000000 -0800
+++ devel-akpm/mm/page_alloc.c	2006-02-27 20:57:55.000000000 -0800
@@ -422,11 +422,6 @@ static void __free_pages_ok(struct page 
 		mutex_debug_check_no_locks_freed(page_address(page),
 						 PAGE_SIZE<<order);
 
-#ifndef CONFIG_MMU
-	for (i = 1 ; i < (1 << order) ; ++i)
-		__put_page(page + i);
-#endif
-
 	for (i = 0 ; i < (1 << order) ; ++i)
 		reserved += free_pages_check(page + i);
 	if (reserved)
@@ -746,7 +741,6 @@ static inline void prep_zero_page(struct
 		clear_highpage(page + i);
 }
 
-#ifdef CONFIG_MMU
 /*
  * split_page takes a non-compound higher-order page, and splits it into
  * n (1<<order) sub-pages: page[0..n]
@@ -766,7 +760,6 @@ void split_page(struct page *page, unsig
 		set_page_count(page + i, 1);
 	}
 }
-#endif
 
 /*
  * Really, prep_compound_page() should be called from __rmqueue_bulk().  But
diff -puN mm/slab.c~mm-nommu-use-compound-pages mm/slab.c
--- devel/mm/slab.c~mm-nommu-use-compound-pages	2006-02-27 20:57:55.000000000 -0800
+++ devel-akpm/mm/slab.c	2006-02-27 20:57:55.000000000 -0800
@@ -590,6 +590,8 @@ static inline void page_set_cache(struct
 
 static inline struct kmem_cache *page_get_cache(struct page *page)
 {
+	if (unlikely(PageCompound(page)))
+		page = (struct page *)page_private(page);
 	return (struct kmem_cache *)page->lru.next;
 }
 
@@ -600,6 +602,8 @@ static inline void page_set_slab(struct 
 
 static inline struct slab *page_get_slab(struct page *page)
 {
+	if (unlikely(PageCompound(page)))
+		page = (struct page *)page_private(page);
 	return (struct slab *)page->lru.prev;
 }
 
@@ -2409,8 +2413,11 @@ static void set_slab_attr(struct kmem_ca
 	struct page *page;
 
 	/* Nasty!!!!!! I hope this is OK. */
-	i = 1 << cachep->gfporder;
 	page = virt_to_page(objp);
+
+	i = 1;
+	if (likely(!PageCompound(page)))
+		i <<= cachep->gfporder;
 	do {
 		page_set_cache(page, cachep);
 		page_set_slab(page, slabp);
_