From: Michael Rubin Subject: Re: [PATCH RFC] Insure direct IO writes do not use the page cache Date: Fri, 31 Jul 2009 11:03:07 -0700 Message-ID: <532480950907311103s422a70acx25c0ab9c56d1ae31@mail.gmail.com> References: <6601abe90907281728h22be79fenc68a16b578e28a91@mail.gmail.com> <20090729181007.GC14105@mit.edu> <20090730183053.GE9223@atrey.karlin.mff.cuni.cz> <20090730203351.GB6833@mit.edu> <1249063137.3917.8.camel@mingming-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Theodore Tso , Jan Kara , Curt Wohlgemuth , ext4 development To: Mingming Return-path: Received: from smtp-out.google.com ([216.239.45.13]:1883 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751897AbZGaSDL (ORCPT ); Fri, 31 Jul 2009 14:03:11 -0400 Received: from zps77.corp.google.com (zps77.corp.google.com [172.25.146.77]) by smtp-out.google.com with ESMTP id n6VI3Bvx004504 for ; Fri, 31 Jul 2009 11:03:11 -0700 Received: from fxm27 (fxm27.prod.google.com [10.184.13.27]) by zps77.corp.google.com with ESMTP id n6VI38iY018718 for ; Fri, 31 Jul 2009 11:03:08 -0700 Received: by fxm27 with SMTP id 27so1218235fxm.11 for ; Fri, 31 Jul 2009 11:03:07 -0700 (PDT) In-Reply-To: <1249063137.3917.8.camel@mingming-laptop> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Jul 31, 2009 at 10:58 AM, Mingming wrote: > Eric and I looked at xfs code together the other day, xfs code did not > ensure DIO sync metadata (conversion) before return back to userspace. > It does ensure the workqueue kickoff the conversion and journal commit, > but it seems not waiting for it to complete. This seems confirmed by xfs > expert on IRC, who expressed DIO means only bypass page cache, but not > necessarily means sync on data and metadata unless file is opened with > SYNC mode. This will our expectations for DIO on ext4 also. mrubin