Index: linux-2.6/mm/filemap_xip.c
===================================================================
--- linux-2.6.orig/mm/filemap_xip.c	2007-09-07 17:54:52.000000000 -0700
+++ linux-2.6/mm/filemap_xip.c	2007-09-07 18:05:54.000000000 -0700
@@ -217,15 +217,19 @@
 	struct inode *inode = mapping->host;
 	struct page *page;
 	pgoff_t size;
+	pgoff_t pgoff = vmf->pgoff >> mapping_order(mapping);
+
+	vmf->base_page_index =
+			vmf->pgoff & ((1 << mapping_order(mapping)) -1);
 
 	/* XXX: are VM_FAULT_ codes OK? */
 
 	size = page_cache_next(mapping, i_size_read(inode));
-	if (vmf->pgoff >= size)
+	if (pgoff >= size)
 		return VM_FAULT_SIGBUS;
 
 	page = mapping->a_ops->get_xip_page(mapping,
-					vmf->pgoff*(PAGE_SIZE/512), 0);
+			vmf->pgoff*(page_cache_size(mapping)/512), 0);
 	if (!IS_ERR(page))
 		goto out;
 	if (PTR_ERR(page) != -ENODATA)
@@ -237,7 +241,7 @@
 	    (!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
 		/* maybe shared writable, allocate new block */
 		page = mapping->a_ops->get_xip_page(mapping,
-					vmf->pgoff*(PAGE_SIZE/512), 1);
+			vmf->pgoff*(page_cache_size(mapping)/512), 1);
 		if (IS_ERR(page))
 			return VM_FAULT_SIGBUS;
 		/* unmap page at pgoff from all other vmas */