[PATCH] mm: split highorder pages

Have an explicit mm call to split higher order pages into individual pages.
 Should help to avoid bugs and be more explicit about the code's intention.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

6 files changed, 12 insertions, 18 deletions

diff --git a/arch/arm/mm/consistent.c b/arch/arm/mm/consistent.c
index c2ee18d2075e..8a1bfcd50087 100644
--- a/arch/arm/mm/consistent.c
+++ b/arch/arm/mm/consistent.c
@@ -223,6 +223,8 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
                 pte = consistent_pte[idx] + off;
                 c->vm_pages = page;
 
+                split_page(page, order);
+
                 /*
                  * Set the "dma handle"
                  */
@@ -231,7 +233,6 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
                 do {
                         BUG_ON(!pte_none(*pte));
 
-                        set_page_count(page, 1);
                         /*
                          * x86 does not mark the pages reserved...
                          */
@@ -250,7 +251,6 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
                  * Free the otherwise unused pages.
                  */
                 while (page < end) {
-                        set_page_count(page, 1);
                         __free_page(page);
                         page++;
                 }
diff --git a/arch/frv/mm/dma-alloc.c b/arch/frv/mm/dma-alloc.c
index 342823aad758..636b2f8b5d98 100644
--- a/arch/frv/mm/dma-alloc.c
+++ b/arch/frv/mm/dma-alloc.c
@@ -115,9 +115,7 @@ void *consistent_alloc(gfp_t gfp, size_t size, dma_addr_t *dma_handle)
          */
         if (order > 0) {
                 struct page *rpage = virt_to_page(page);
-
-                for (i = 1; i < (1 << order); i++)
-                        set_page_count(rpage + i, 1);
+                split_page(rpage, order);
         }
 
         err = 0;
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 0ff9a348b843..a140da9732db 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -54,7 +54,8 @@ unsigned long empty_zero_page, zero_page_mask;
  */
 unsigned long setup_zero_pages(void)
 {
-        unsigned long order, size;
+        unsigned int order;
+        unsigned long size;
         struct page *page;
 
         if (cpu_has_vce)
@@ -67,9 +68,9 @@ unsigned long setup_zero_pages(void)
                 panic("Oh boy, that early out of memory?");
 
         page = virt_to_page(empty_zero_page);
+        split_page(page, order);
         while (page < virt_to_page(empty_zero_page + (PAGE_SIZE << order))) {
                 SetPageReserved(page);
-                set_page_count(page, 1);
                 page++;
         }
 
diff --git a/arch/ppc/kernel/dma-mapping.c b/arch/ppc/kernel/dma-mapping.c
index 685fd0defe23..61465ec88bc7 100644
--- a/arch/ppc/kernel/dma-mapping.c
+++ b/arch/ppc/kernel/dma-mapping.c
@@ -223,6 +223,8 @@ __dma_alloc_coherent(size_t size, dma_addr_t *handle, gfp_t gfp)
                 pte_t *pte = consistent_pte + CONSISTENT_OFFSET(vaddr);
                 struct page *end = page + (1 << order);
 
+                split_page(page, order);
+
                 /*
                  * Set the "dma handle"
                  */
@@ -231,7 +233,6 @@ __dma_alloc_coherent(size_t size, dma_addr_t *handle, gfp_t gfp)
                 do {
                         BUG_ON(!pte_none(*pte));
 
-                        set_page_count(page, 1);
                         SetPageReserved(page);
                         set_pte_at(&init_mm, vaddr,
                                    pte, mk_pte(page, pgprot_noncached(PAGE_KERNEL)));
@@ -244,7 +245,6 @@ __dma_alloc_coherent(size_t size, dma_addr_t *handle, gfp_t gfp)
                  * Free the otherwise unused pages.
                  */
                 while (page < end) {
-                        set_page_count(page, 1);
                         __free_page(page);
                         page++;
                 }
diff --git a/arch/sh/mm/consistent.c b/arch/sh/mm/consistent.c
index df3a9e452cc5..ee73e30263af 100644
--- a/arch/sh/mm/consistent.c
+++ b/arch/sh/mm/consistent.c
@@ -23,6 +23,7 @@ void *consistent_alloc(gfp_t gfp, size_t size, dma_addr_t *handle)
         page = alloc_pages(gfp, order);
         if (!page)
                 return NULL;
+        split_page(page, order);
 
         ret = page_address(page);
         *handle = virt_to_phys(ret);
@@ -37,8 +38,6 @@ void *consistent_alloc(gfp_t gfp, size_t size, dma_addr_t *handle)
         end  = page + (1 << order);
 
         while (++page < end) {
-                set_page_count(page, 1);
-
                 /* Free any unused pages */
                 if (page >= free) {
                         __free_page(page);
diff --git a/arch/xtensa/mm/pgtable.c b/arch/xtensa/mm/pgtable.c
index cbc56aedf13e..7d28914d11cb 100644
--- a/arch/xtensa/mm/pgtable.c
+++ b/arch/xtensa/mm/pgtable.c
@@ -21,13 +21,9 @@ pte_t* pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
         p = (pte_t*) __get_free_pages(GFP_KERNEL|__GFP_REPEAT, COLOR_ORDER);
 
         if (likely(p)) {
-                struct page *page;
+                split_page(virt_to_page(p), COLOR_ORDER);
 
                 for (i = 0; i < COLOR_SIZE; i++) {
-                        page = virt_to_page(p);
-
-                        set_page_count(page, 1);
-
                         if (ADDR_COLOR(p) == color)
                                 pte = p;
                         else
@@ -55,9 +51,9 @@ struct page* pte_alloc_one(struct mm_struct *mm, unsigned long address)
         p = alloc_pages(GFP_KERNEL | __GFP_REPEAT, PTE_ORDER);
 
         if (likely(p)) {
-                for (i = 0; i < PAGE_ORDER; i++) {
-                        set_page_count(p, 1);
+                split_page(p, COLOR_ORDER);
 
+                for (i = 0; i < PAGE_ORDER; i++) {
                         if (PADDR_COLOR(page_address(p)) == color)
                                 page = p;
                         else