From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31AC8C433E2 for ; Fri, 19 Jun 2020 22:11:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A254208DB for ; Fri, 19 Jun 2020 22:11:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729033AbgFSWLA (ORCPT ); Fri, 19 Jun 2020 18:11:00 -0400 Received: from mail107.syd.optusnet.com.au ([211.29.132.53]:50638 "EHLO mail107.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728906AbgFSWLA (ORCPT ); Fri, 19 Jun 2020 18:11:00 -0400 Received: from dread.disaster.area (pa49-180-124-177.pa.nsw.optusnet.com.au [49.180.124.177]) by mail107.syd.optusnet.com.au (Postfix) with ESMTPS id C9D62D5C875; Sat, 20 Jun 2020 08:10:50 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1jmPDg-0000mg-Il; Sat, 20 Jun 2020 08:10:44 +1000 Date: Sat, 20 Jun 2020 08:10:44 +1000 From: Dave Chinner To: "J. Bruce Fields" Cc: Masayoshi Mizuma , Eric Sandeen , "Darrick J. Wong" , Christoph Hellwig , Theodore Ts'o , Andreas Dilger , Alexander Viro , Masayoshi Mizuma , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-xfs , jlayton@redhat.com Subject: Re: [PATCH] fs: i_version mntopt gets visible through /proc/mounts Message-ID: <20200619221044.GO2005@dread.disaster.area> References: <20200617181816.GA18315@fieldses.org> <4cbb5cbe-feb4-2166-0634-29041a41a8dc@sandeen.net> <20200617184507.GB18315@fieldses.org> <20200618013026.ewnhvf64nb62k2yx@gabell> <20200618030539.GH2005@dread.disaster.area> <20200618034535.h5ho7pd4eilpbj3f@gabell> <20200618223948.GI2005@dread.disaster.area> <20200619022005.GA25414@fieldses.org> <20200619024455.GN2005@dread.disaster.area> <20200619204033.GB1564@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200619204033.GB1564@fieldses.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=QIgWuTDL c=1 sm=1 tr=0 a=k3aV/LVJup6ZGWgigO6cSA==:117 a=k3aV/LVJup6ZGWgigO6cSA==:17 a=kj9zAlcOel0A:10 a=nTHF0DUjJn0A:10 a=7-415B0cAAAA:8 a=eqXBFi9LVwU8ObKSOJUA:9 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Jun 19, 2020 at 04:40:33PM -0400, J. Bruce Fields wrote: > On Fri, Jun 19, 2020 at 12:44:55PM +1000, Dave Chinner wrote: > > On Thu, Jun 18, 2020 at 10:20:05PM -0400, J. Bruce Fields wrote: > > > My memory was that after Jeff Layton's i_version patches, there wasn't > > > really a significant performance hit any more, so the ability to turn it > > > off is no longer useful. > > > > Yes, I completely agree with you here. However, with some > > filesystems allowing it to be turned off, we can't just wave our > > hands and force enable the option. Those filesystems - if the > > maintainers chose to always enable iversion - will have to go > > through a mount option deprecation period before permanently > > enabling it. > > I don't understand why. > > The filesystem can continue to let people set iversion or noiversion as > they like, while under the covers behaving as if iversion is always set. > I can't see how that would break any application. (Or even how an > application would be able to detect that the filesystem was doing this.) It doesn't break functionality, but it affects performance. IOWs, it can make certain workloads go a lot slower in some circumstances. And that can result in unexectedly breaking SLAs or slow down a complex, finely tuned data center wide workload to the point it no longer meets requirements. Such changes in behaviour are considered a regression, especially if they result from a change that just ignores the mount option that turned off that specific feature. Cheers, Dave. -- Dave Chinner david@fromorbit.com