--- /dev/null 2008-03-30 12:15:48.586669308 +0200
+++ linux-2.6.24logfs/fs/logfs/file.c 2008-03-28 18:26:27.421722776 +0100
@@ -0,0 +1,236 @@
+/*
+ * fs/logfs/file.c - prepare_write, commit_write and friends
+ *
+ * As should be obvious for Linux kernel code, license is GPLv2
+ *
+ * Copyright (c) 2005-2007 Joern Engel <joern@logfs.org>
+ */
+#include "logfs.h"
+#include <linux/sched.h>
+#include <linux/writeback.h>
+
+static int logfs_prepare_write(struct file *file, struct page *page,
+ unsigned start, unsigned end)
+{
+ if (PageUptodate(page))
+ return 0;
+
+ if ((start == 0) && (end == PAGE_CACHE_SIZE))
+ return 0;
+
+ return logfs_readpage_nolock(page);
+}
+
+static int logfs_commit_write(struct file *file, struct page *page,
+ unsigned start, unsigned end)
+{
+ struct inode *inode = page->mapping->host;
+ pgoff_t index = page->index;
+ int ret;
+
+ BUG_ON(PAGE_CACHE_SIZE != inode->i_sb->s_blocksize);
+ BUG_ON(page->index > I3_BLOCKS);
+
+ if (start == end)
+ return 0; /* FIXME: do we need to update inode? */
+
+ if (i_size_read(inode) < (index << PAGE_CACHE_SHIFT) + end) {
+ i_size_write(inode, (index << PAGE_CACHE_SHIFT) + end);
+ mark_inode_dirty_sync(inode);
+ }
+
+ ClearPageZero(page);
+ ret = logfs_write_buf(inode, page, NULL, WF_LOCK);
+ return ret;
+}
+
+int logfs_readpage(struct file *file, struct page *page)
+{
+ int ret;
+
+ ret = logfs_readpage_nolock(page);
+ unlock_page(page);
+ return ret;
+}
+
+/* Clear the page's dirty flag in the radix tree. */
+/* TODO: mucking with PageWriteback is silly. Add a generic function to clear
+ * the dirty bit from the radix tree for filesystems that don't have to wait
+ * for page writeback to finish (i.e. any compressing filesystem).
+ */
+static void clear_radix_tree_dirty(struct page *page)
+{
+ BUG_ON(PagePrivate(page) || page->private);
+ set_page_writeback(page);
+ end_page_writeback(page);
+}
+
+static int __logfs_writepage(struct page *page, struct writeback_control ...
