Stop fallback_migrate_page() from using page_has_buffers() since that might not
be available.  Use PagePrivate() instead since that's more general.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
         * Buffers may be managed in a filesystem specific way.
         * We must have no buffers or drop them.
         */
-       if (page_has_buffers(page) &&
+       if (PagePrivate(page) &&
            !try_to_release_page(page, GFP_KERNEL))
                return -EAGAIN;