New migration scheme

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

Index: linux-2.6.16-mm2/mm/migrate.c
===================================================================
--- linux-2.6.16-mm2.orig/mm/migrate.c	2006-03-31 09:29:32.000000000 -0800
+++ linux-2.6.16-mm2/mm/migrate.c	2006-03-31 09:38:29.000000000 -0800
@@ -139,8 +139,9 @@ int migrate_page_remove_references(struc
 	 * indicates that the page is in use or truncate has removed
 	 * the page.
 	 */
-	if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
-		return -EAGAIN;
+	if (!page->mapping ||
+		page_mapcount(page) + nr_refs + !!mapping != page_count(page))
+			return -EAGAIN;
 
 	/*
 	 * Establish swap ptes for anonymous pages or destroy pte
@@ -171,13 +172,19 @@ int migrate_page_remove_references(struc
 	if (page_mapcount(page))
 		return -EAGAIN;
 
+	if (!mapping)
+		return 0;	/* Anonymous page without swap */
+
+	/*
+	 * Page has a mapping that we need to change
+	 */
 	write_lock_irq(&mapping->tree_lock);
 
 	radix_pointer = (struct page **)radix_tree_lookup_slot(
 						&mapping->page_tree,
 						page_index(page));
 
-	if (!page_mapping(page) || page_count(page) != nr_refs ||
+	if (!page_mapping(page) || page_count(page) != nr_refs + 1 ||
 			*radix_pointer != page) {
 		write_unlock_irq(&mapping->tree_lock);
 		return -EAGAIN;
@@ -259,10 +269,12 @@ int migrate_page(struct page *newpage, s
 
 	BUG_ON(PageWriteback(page));	/* Writeback must be complete */
 
-	rc = migrate_page_remove_references(newpage, page, 2);
+	rc = migrate_page_remove_references(newpage, page, 1);
 
-	if (rc)
+	if (rc) {
+		remove_migration_ptes(page, page);
 		return rc;
+	}
 
 	migrate_page_copy(newpage, page);
 
@@ -274,7 +286,7 @@ int migrate_page(struct page *newpage, s
 	 * waiting on the page lock to use the new page via the page tables
 	 * before the new page is unlocked.
 	 */
-	remove_from_swap(newpage);
+	remove_migration_ptes(page, newpage);
 	return 0;
 }
 EXPORT_SYMBOL(migrate_page);
@@ -356,9 +368,12 @@ redo:
 		 * Try to migrate the page.
 		 */
 		mapping = page_mapping(page);
-		if (!mapping)
+		if (!mapping) {
+
+			rc = migrate_page(newpage, page);
 			goto unlock_both;
 
+		} else
 		if (mapping->a_ops->migratepage) {
 			/*
 			 * Most pages have a mapping and most filesystems
@@ -450,7 +465,7 @@ int buffer_migrate_page(struct page *new
 
 	head = page_buffers(page);
 
-	rc = migrate_page_remove_references(newpage, page, 3);
+	rc = migrate_page_remove_references(newpage, page, 2);
 
 	if (rc)
 		return rc;