Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753442AbZIGOIT (ORCPT ); Mon, 7 Sep 2009 10:08:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753331AbZIGOIT (ORCPT ); Mon, 7 Sep 2009 10:08:19 -0400 Received: from smtp.nokia.com ([192.100.105.134]:44273 "EHLO mgw-mx09.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753213AbZIGOIS (ORCPT ); Mon, 7 Sep 2009 10:08:18 -0400 Message-ID: <4AA513AA.3010206@nokia.com> Date: Mon, 07 Sep 2009 17:07:38 +0300 From: Adrian Hunter User-Agent: Thunderbird 2.0.0.21 (X11/20090318) MIME-Version: 1.0 To: Nick Piggin CC: chris.mason@oracle.com, david@fromorbit.com, Andrew Morton , "Bityutskiy Artem (Nokia-M/Helsinki)" , LKML Subject: [RFC][PATCH] mm: write_cache_pages be more sequential Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 07 Sep 2009 14:07:13.0188 (UTC) FILETIME=[7F73EE40:01CA2FC4] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1780 Lines: 49 >From 6f3bb7c26936c45d810048f59c369e8d5a5623fc Mon Sep 17 00:00:00 2001 From: Adrian Hunter Date: Mon, 7 Sep 2009 10:49:11 +0300 Subject: [PATCH] mm: write_cache_pages be more sequential If a file is written to sequentially, then writeback should write the pages sequentially also. However, that does not always happen. For example: 1) user writes pages 0, 1 and 2 but 2 is incomplete 2) write_cache_pages writes pages 0, 1 and 2 and sets writeback_index to 3 3) user finishes writing page 2 and writes pages 3 and 4 4) write_cache_pages writes pages 3 and 4, and then cycles back and writes page 2 again. So the pages are written out in the order 0, 1, 2, 3 ,4 ,2 instead of 0, 1, 2, 2, 3, 4. This situation was noticed on UBIFS because it writes directly from writepage. Hence if there is an unexpected power-loss, a file will end up with a hole even though the file was written sequentially by the user. Signed-off-by: Adrian Hunter --- mm/page-writeback.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 81627eb..7410b7a 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -960,6 +960,8 @@ int write_cache_pages(struct address_space *mapping, pagevec_init(&pvec, 0); if (wbc->range_cyclic) { writeback_index = mapping->writeback_index; /* prev offset */ + if (writeback_index) + writeback_index -= 1; index = writeback_index; if (index == 0) cycled = 1; -- 1.5.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/