Variable Order Page Cache: Add clearing and flushing function

Add a flushing and clearing function for higher order pages.
These are provisional and will likely have to be optimized.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 fs/libfs.c              |    6 +++---
 include/linux/highmem.h |    9 +++------
 include/linux/pagemap.h |   25 +++++++++++++++++++++++++
 mm/filemap.c            |    4 ++--
 4 files changed, 33 insertions(+), 11 deletions(-)

Index: linux-2.6.21-rc7-mm2/include/linux/pagemap.h
===================================================================
--- linux-2.6.21-rc7-mm2.orig/include/linux/pagemap.h	2007-04-26 22:35:42.000000000 -0700
+++ linux-2.6.21-rc7-mm2/include/linux/pagemap.h	2007-04-26 22:35:47.000000000 -0700
@@ -325,6 +325,31 @@ static inline void wait_on_page_writebac
 
 extern void end_page_writeback(struct page *page);
 
+/* Support for clearing higher order pages */
+static inline void clear_mapping_page(struct page *page)
+{
+	int nr_pages = compound_pages(page);
+	int i;
+
+	for (i = 0; i < nr_pages; i++)
+		clear_highpage(page + i);
+}
+
+/*
+ * Support for flushing higher order pages.
+ *
+ * A bit stupid: On many platforms flushing the first page
+ * will flush any TLB starting there
+ */
+static inline void flush_mapping_page(struct page *page)
+{
+	int nr_pages = compound_pages(page);
+	int i;
+
+	for (i = 0; i < nr_pages; i++)
+		flush_dcache_page(page + i);
+}
+
 /*
  * Fault a userspace page into pagetables.  Return non-zero on a fault.
  *
Index: linux-2.6.21-rc7-mm2/fs/libfs.c
===================================================================
--- linux-2.6.21-rc7-mm2.orig/fs/libfs.c	2007-04-26 22:35:45.000000000 -0700
+++ linux-2.6.21-rc7-mm2/fs/libfs.c	2007-04-26 22:35:47.000000000 -0700
@@ -326,8 +326,8 @@ int simple_rename(struct inode *old_dir,
 
 int simple_readpage(struct file *file, struct page *page)
 {
-	clear_highpage(page);
-	flush_dcache_page(page);
+	clear_mapping_page(page);
+	flush_mapping_page(page);
 	SetPageUptodate(page);
 	unlock_page(page);
 	return 0;
@@ -339,7 +339,7 @@ int simple_prepare_write(struct file *fi
 	unsigned int page_size = page_cache_size(file->f_mapping);
 
 	if (!PageUptodate(page)) {
-		if (to - from != page_size)
+		if (to - from != page_size) {
 			if (from)
 				zero_user_page(page, 0, from, KM_USER0);
 			if (to < page_size)
Index: linux-2.6.21-rc7-mm2/include/linux/highmem.h
===================================================================
--- linux-2.6.21-rc7-mm2.orig/include/linux/highmem.h	2007-04-26 22:34:50.000000000 -0700
+++ linux-2.6.21-rc7-mm2/include/linux/highmem.h	2007-04-26 22:35:47.000000000 -0700
@@ -148,15 +148,12 @@ static inline void clear_highpage(struct
 								\
 		kaddr = kmap_atomic(page, km_type);		\
 		memset((char *)kaddr + (offset), 0, (size));	\
-		flush_dcache_page(page);			\
+		flush_mapping_page(page);			\
 		kunmap_atomic(kaddr, (km_type));		\
 	} while (0)
 
-static inline void __deprecated memclear_highpage_flush(struct page *page,
-			unsigned int offset, unsigned int size)
-{
-	zero_user_page(page, offset, size, KM_USER0);
-}
+#define memclear_highpage_flush(__p, __o, __s) \
+	zero_user_page(__p, __o, __s, KM_USER0)
 
 #ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE
 
Index: linux-2.6.21-rc7-mm2/mm/filemap.c
===================================================================
--- linux-2.6.21-rc7-mm2.orig/mm/filemap.c	2007-04-26 22:35:45.000000000 -0700
+++ linux-2.6.21-rc7-mm2/mm/filemap.c	2007-04-26 22:35:47.000000000 -0700
@@ -974,7 +974,7 @@ page_ok:
 		 * before reading the page on the kernel side.
 		 */
 		if (mapping_writably_mapped(mapping))
-			flush_dcache_page(page);
+			flush_mapping_page(page);
 
 		/*
 		 * When a sequential read accesses a page several times,
@@ -2044,7 +2044,7 @@ generic_file_buffered_write(struct kiocb
 		else
 			copied = filemap_copy_from_user_iovec(page, offset,
 						cur_iov, iov_base, bytes);
-		flush_dcache_page(page);
+		flush_mapping_page(page);
 		status = a_ops->commit_write(file, page, offset, offset+bytes);
 		if (status == AOP_TRUNCATED_PAGE) {
 			page_cache_release(page);