From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757988Ab1DMJGw (ORCPT ); Wed, 13 Apr 2011 05:06:52 -0400 Received: from mga01.intel.com ([192.55.52.88]:1489 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757909Ab1DMJGt (ORCPT ); Wed, 13 Apr 2011 05:06:49 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,203,1301900400"; d="scan'208";a="678447181" Message-Id: <20110413090415.511675208@intel.com> User-Agent: quilt/0.48-1 Date: Wed, 13 Apr 2011 16:59:39 +0800 From: Wu Fengguang To: Andrew Morton cc: Peter Zijlstra , Wu Fengguang cc: Jan Kara cc: Dave Chinner cc: Hugh Dickins , Rik van Riel Cc: LKML cc: Linux Memory Management List , Subject: [PATCH 2/4] writeback: avoid duplicate balance_dirty_pages_ratelimited() calls References: <20110413085937.981293444@intel.com> Content-Disposition: inline; filename=writeback-fix-duplicate-bdp-calls.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When dd in 512bytes, balance_dirty_pages_ratelimited() could be called 8 times for the same page, but obviously the page is only dirtied once. Fix it with a (slightly racy) PageDirty() test. Signed-off-by: Wu Fengguang --- mm/filemap.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- linux-next.orig/mm/filemap.c 2011-04-13 16:46:01.000000000 +0800 +++ linux-next/mm/filemap.c 2011-04-13 16:47:26.000000000 +0800 @@ -2313,6 +2313,7 @@ static ssize_t generic_perform_write(str long status = 0; ssize_t written = 0; unsigned int flags = 0; + unsigned int dirty; /* * Copies from kernel address space cannot fail (NFSD is a big user). @@ -2361,6 +2362,7 @@ again: pagefault_enable(); flush_dcache_page(page); + dirty = PageDirty(page); mark_page_accessed(page); status = a_ops->write_end(file, mapping, pos, bytes, copied, page, fsdata); @@ -2387,7 +2389,8 @@ again: pos += copied; written += copied; - balance_dirty_pages_ratelimited(mapping); + if (!dirty) + balance_dirty_pages_ratelimited(mapping); } while (iov_iter_count(i));