From: "Jayson R. King" Subject: [09/11] vfs: Add no_nrwrite_index_update writeback control flag Date: Sat, 27 Feb 2010 00:33:15 -0600 Message-ID: <4B88BCAB.7000205@jaysonking.com> References: <4B88BA1B.4050500@jaysonking.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Aneesh Kumar K.V" , Mingming Cao , Theodore Ts'o , linux-ext4@vger.kernel.org, Andrew Morton , Jayson King To: LKML , Stable team , Greg Kroah-Hartman Return-path: Received: from bosmailout07.eigbox.net ([66.96.187.7]:48415 "EHLO bosmailout07.eigbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967854Ab0B0HXj (ORCPT ); Sat, 27 Feb 2010 02:23:39 -0500 In-Reply-To: <4B88BA1B.4050500@jaysonking.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Aneesh Kumar K.V Date: Thu Oct 16 10:09:17 2008 -0400 Subject: vfs: Add no_nrwrite_index_update writeback control flag commit 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 upstream. If no_nrwrite_index_update is set we don't update nr_to_write and address space writeback_index in write_cache_pages. This change enables a file system to skip these updates in write_cache_pages and do them in the writepages() callback. This patch will be followed by an ext4 patch that make use of these new flags. Signed-off-by: Aneesh Kumar K.V Signed-off-by: "Theodore Ts'o" CC: linux-fsdevel@vger.kernel.org [dev@jaysonking.com: Modified the patch to account for subsequent changes in mainline being cherry-picked earlier for 2.6.27.y.] Signed-off-by: Jayson R. King --- include/linux/writeback.h | 9 +++++++++ mm/page-writeback.c | 14 +++++++++----- 2 files changed, 18 insertions(+), 5 deletions(-) diff -urNp linux-2.6.27.orig/include/linux/writeback.h linux-2.6.27/include/linux/writeback.h --- linux-2.6.27.orig/include/linux/writeback.h 2010-02-26 14:26:43.084252730 -0600 +++ linux-2.6.27/include/linux/writeback.h 2010-02-26 14:26:48.468252521 -0600 @@ -62,6 +62,15 @@ struct writeback_control { unsigned for_writepages:1; /* This is a writepages() call */ unsigned range_cyclic:1; /* range_start is cyclic */ unsigned more_io:1; /* more io to be dispatched */ + /* + * write_cache_pages() won't update wbc->nr_to_write and + * mapping->writeback_index if no_nrwrite_index_update + * is set. write_cache_pages() may write more than we + * requested and we want to make sure nr_to_write and + * writeback_index are updated in a consistent manner + * so we use a single control to update them + */ + unsigned no_nrwrite_index_update:1; }; /* diff -urNp linux-2.6.27.orig/mm/page-writeback.c linux-2.6.27/mm/page-writeback.c --- linux-2.6.27.orig/mm/page-writeback.c 2010-02-26 14:26:43.085252646 -0600 +++ linux-2.6.27/mm/page-writeback.c 2010-02-26 14:26:48.469252852 -0600 @@ -878,6 +878,7 @@ int write_cache_pages(struct address_spa pgoff_t done_index; int cycled; int range_whole = 0; + long nr_to_write = wbc->nr_to_write; if (wbc->nonblocking && bdi_write_congested(bdi)) { wbc->encountered_congestion = 1; @@ -985,9 +986,9 @@ continue_unlock: } } - if (wbc->nr_to_write > 0) { - wbc->nr_to_write--; - if (wbc->nr_to_write == 0 && + if (nr_to_write > 0) { + nr_to_write--; + if (nr_to_write == 0 && wbc->sync_mode == WB_SYNC_NONE) { /* * We stop writing back only if we are @@ -1024,8 +1025,11 @@ continue_unlock: end = writeback_index - 1; goto retry; } - if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) - mapping->writeback_index = done_index; + if (!wbc->no_nrwrite_index_update) { + if (wbc->range_cyclic || (range_whole && nr_to_write > 0)) + mapping->writeback_index = done_index; + wbc->nr_to_write = nr_to_write; + } return ret; }