+static int btree_migratepage(struct address_space *mapping,
+ struct page *newpage, struct page *page)
+{
+ /*
+ * we can't safely write a btree page from here,
+ * we haven't done the locking hook
+ */
+ if (PageDirty(page))
+ return -EAGAIN;
+ /*
+ * Buffers may be managed in a filesystem specific way.
+ * We must have no buffers or drop them.
+ */
+ if (page_has_private(page) &&
+ !try_to_release_page(page, GFP_KERNEL))
+ return -EAGAIN;
+#ifdef CONFIG_MIGRATION
+ return migrate_page(mapping, newpage, page);
+#else
+ return -ENOSYS;
+#endif
+}
+