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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 14677C433EF for ; Wed, 30 Mar 2022 21:02:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344477AbiC3VEI (ORCPT ); Wed, 30 Mar 2022 17:04:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231735AbiC3VEI (ORCPT ); Wed, 30 Mar 2022 17:04:08 -0400 Received: from mail104.syd.optusnet.com.au (mail104.syd.optusnet.com.au [211.29.132.246]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E062942EF4 for ; Wed, 30 Mar 2022 14:02:22 -0700 (PDT) Received: from dread.disaster.area (pa49-180-43-123.pa.nsw.optusnet.com.au [49.180.43.123]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id B1C325341AB; Thu, 31 Mar 2022 08:02:20 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1nZfSN-00Bpo5-2A; Thu, 31 Mar 2022 08:02:19 +1100 Date: Thu, 31 Mar 2022 08:02:19 +1100 From: Dave Chinner To: Steven Rostedt Cc: Chris Down , Petr Mladek , Jonathan Lassoff , linux-xfs@vger.kernel.org, "Darrick J. Wong" , Sergey Senozhatsky , John Ogness Subject: Re: [PATCH v3 2/2] Add XFS messages to printk index Message-ID: <20220330210219.GD1544202@dread.disaster.area> References: <3e1f6011b22ca87ea3c0fad701286369daa2187f.1648228733.git.jof@thejof.com> <3c3ae424913cb921a9f8abddfcb1b418e7cfa601.1648228733.git.jof@thejof.com> <20220330003457.GB1544202@dread.disaster.area> <20220330124739.70edca36@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220330124739.70edca36@gandalf.local.home> X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.4 cv=deDjYVbe c=1 sm=1 tr=0 ts=6244c55e a=MV6E7+DvwtTitA3W+3A2Lw==:117 a=MV6E7+DvwtTitA3W+3A2Lw==:17 a=kj9zAlcOel0A:10 a=o8Y5sQTvuykA:10 a=07d9gI8wAAAA:8 a=7-415B0cAAAA:8 a=mMpGT428DGEWo3aVKB0A:9 a=CjuIK1q_8ugA:10 a=e2CUPOnPG4QKp8I52DXD:22 a=biEYGPWJfzWAr4FL6Ov7:22 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, Mar 30, 2022 at 12:47:39PM -0400, Steven Rostedt wrote: > On Wed, 30 Mar 2022 12:52:58 +0100 > Chris Down wrote: > > > The policy, as with all debugfs APIs by default, is that it's completely > > unstable and there are no API stability guarantees whatsoever. That's why > > there's no extensive documentation for users: because this is a feature for > > kernel developers. > > > > 0: https://lwn.net/Articles/309298/ > > That article you reference states the opposite of what you said. And I got > burnt by it before. Because Linus stated, if it is available for users, it > is an ABI. > > From the article above: > > "Linus put it this way: > > The fact that something is documented (whether correctly or not) has > absolutely _zero_ impact on anything at all. What makes something an ABI is > that it's useful and available. The only way something isn't an ABI is by > _explicitly_ making sure that it's not available even by mistake in a > stable form for binary use. Example: kernel internal data structures and > function calls. We make sure that you simply _cannot_ make a binary that > works across kernel versions. That is the only way for an ABI to not form." > > IOW, files in debugfs are available for users, and if something is written > that depends on it and it is useful, it becomes ABI. Yup, that's exactly what happened with powertop and the tracepoints it used and why I pointed to it as is the canonical example of information exposed from within debugfs unintentionally becoming stable KABI.... Cheers, Dave. -- Dave Chinner david@fromorbit.com