From: Andreas Dilger Subject: Re: [PATCH] ext3: wait on all pending commits in ext3_sync_fs Date: Mon, 22 Dec 2008 15:57:57 -0700 Message-ID: <20081222225757.GV5000@webber.adilger.int> References: <4908C951.2000309@redhat.com> <20081103184426.GA31894@ajones-laptop.nbttech.com> <20081103113318.35b0c266.akpm@linux-foundation.org> <20081103201428.GB30565@ajones-laptop.nbttech.com> <20081218231707.GB20092@atrey.karlin.mff.cuni.cz> <494ADEB3.8010109@redhat.com> <20081219002752.GE8424@duck.suse.cz> <494AFA16.2010004@redhat.com> <494FE73E.5000802@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7BIT Cc: Eric Sandeen , Jan Kara , Arthur Jones , Andrew Morton , "linux-ext4@vger.kernel.org" , "sct@redhat.com" , "linux-kernel@vger.kernel.org" To: Ric Wheeler Return-path: Received: from sca-es-mail-1.Sun.COM ([192.18.43.132]:40774 "EHLO sca-es-mail-1.sun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753593AbYLVW6O (ORCPT ); Mon, 22 Dec 2008 17:58:14 -0500 In-reply-to: <494FE73E.5000802@redhat.com> Content-disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: On Dec 22, 2008 14:15 -0500, Ric Wheeler wrote: > Without having dived into the patch in detail, one worry I would have is > that we still might care to spin up a drive for empty transactions in > order to invalidate the drive's write cache. > > For example, if we have the following sequence: > > (1) user app performs series of writes to file A > (2) pages dirtied from writes to A are destaged to the disk over time > (3) user app issues fsync(file A) to make sure that the data will > survive a power outage > > At this point in time, would this change prevent us from spinning up the > drive and invalidating the disk write cache for that fsync() ? Well, if the writes themselves didn't spin up the drive, it is uncertain whether the write of the journal commit block would be any more helpful in getting that to happen. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.