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Subject[27/36] Compound page zeroing and flushing
We may now have to zero and flush higher order pages. Implement
clear_mapping_page and flush_mapping_page to do that job. Replace
the flushing and clearing at some key locations for the pagecache.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
---
fs/libfs.c | 4 ++--
include/linux/highmem.h | 31 +++++++++++++++++++++++++++++--
mm/filemap.c | 4 ++--
mm/filemap_xip.c | 4 ++--
4 files changed, 35 insertions(+), 8 deletions(-)
Index: linux-2.6/fs/libfs.c
===================================================================
--- linux-2.6.orig/fs/libfs.c 2007-08-27 20:51:55.000000000 -0700
+++ linux-2.6/fs/libfs.c 2007-08-27 21:08:04.000000000 -0700
@@ -330,8 +330,8 @@ 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;
Index: linux-2.6/include/linux/highmem.h
===================================================================
--- linux-2.6.orig/include/linux/highmem.h 2007-08-27 19:22:17.000000000 -0700
+++ linux-2.6/include/linux/highmem.h 2007-08-27 21:08:04.000000000 -0700
@@ -124,14 +124,41 @@ static inline void clear_highpage(struct
kunmap_atomic(kaddr, KM_USER0);
}

+/*
+ * Clear a higher order page
+ */
+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);
+}
+
+/*
+ * Primitive 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);
+}
+
static inline void zero_user_segments(struct page *page,
unsigned start1, unsigned end1,
unsigned start2, unsigned end2)
{
void *kaddr = kmap_atomic(page, KM_USER0);

- BUG_ON(end1 > PAGE_SIZE ||
- end2 > PAGE_SIZE);
+ BUG_ON(end1 > compound_size(page) ||
+ end2 > compound_size(page));

if (end1 > start1)
memset(kaddr + start1, 0, end1 - start1);
Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c 2007-08-27 19:31:13.000000000 -0700
+++ linux-2.6/mm/filemap.c 2007-08-27 21:08:04.000000000 -0700
@@ -941,7 +941,7 @@ 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,
@@ -1932,7 +1932,7 @@ 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);
Index: linux-2.6/mm/filemap_xip.c
===================================================================
--- linux-2.6.orig/mm/filemap_xip.c 2007-08-27 20:51:40.000000000 -0700
+++ linux-2.6/mm/filemap_xip.c 2007-08-27 21:08:04.000000000 -0700
@@ -104,7 +104,7 @@ do_xip_mapping_read(struct address_space
* before reading the page on the kernel side.
*/
if (mapping_writably_mapped(mapping))
- flush_dcache_page(page);
+ flush_mapping_page(page);

/*
* Ok, we have the page, so now we can copy it to user space...
@@ -320,7 +320,7 @@ __xip_file_write(struct file *filp, cons
}

copied = filemap_copy_from_user(page, offset, buf, bytes);
- flush_dcache_page(page);
+ flush_mapping_page(page);
if (likely(copied > 0)) {
status = copied;

--
-
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