From: "Jayson R. King" Subject: Re: [PATCH 2.6.27.y 1/3] ext4: Use our own write_cache_pages() Date: Fri, 28 May 2010 20:41:44 -0500 Message-ID: <4C0070D8.8060500@jaysonking.com> References: <4C001888.8020006@jaysonking.com> <4C0018E1.5060007@jaysonking.com> <20100529004913.GL26177@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Jayson R. King" , Stable team , LKML , Greg Kroah-Hartman , "Aneesh Kumar K.V" , Dave Chinner , Ext4 Developers List , Kay Diederichs To: tytso@mit.edu Return-path: Received: from bosmailout08.eigbox.net ([66.96.189.8]:51472 "EHLO bosmailout08.eigbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752244Ab0E2COI (ORCPT ); Fri, 28 May 2010 22:14:08 -0400 In-Reply-To: <20100529004913.GL26177@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 05/28/2010 07:49 PM, tytso@mit.edu wrote: > This doesn't fix a bug; it's to make it easy for Dave Chinner to make > some changes to fix XFS's performance and to undo some ext4-specific > changes to write_cache_pages(). I'm not sure there's a good reason to > backport this to 2.6.27.y.... The difference is that, 2.6.27's write_cache_pages() in page-writeback.c still updates wbc->nr_to_write, since the patch which changed that behavior was dropped from .27-rc2 due to the XFS regression it causes on mainline. ext4 appears to want the behavior of write_cache_pages which does not update wbc->nr_to_write. This write_cache_pages_da() does what ext4 wants, without introducing the XFS regression. So I believe it is needed. Did I mis-judge? Rgds, Jayson