From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:46803 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726536AbfF0WhH (ORCPT ); Thu, 27 Jun 2019 18:37:07 -0400 Date: Fri, 28 Jun 2019 08:35:57 +1000 From: Dave Chinner Subject: Re: [PATCH 12/12] iomap: add tracing for the address space operations Message-ID: <20190627223557.GI7777@dread.disaster.area> References: <20190624055253.31183-1-hch@lst.de> <20190624055253.31183-13-hch@lst.de> <20190624234921.GE7777@dread.disaster.area> <20190625101515.GL1462@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190625101515.GL1462@lst.de> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Christoph Hellwig Cc: "Darrick J . Wong" , Damien Le Moal , Andreas Gruenbacher , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org On Tue, Jun 25, 2019 at 12:15:15PM +0200, Christoph Hellwig wrote: > On Tue, Jun 25, 2019 at 09:49:21AM +1000, Dave Chinner wrote: > > > +#undef TRACE_SYSTEM > > > +#define TRACE_SYSTEM iomap > > > > Can you add a comment somewhere here that says these tracepoints are > > volatile and we reserve the right to change them at any time so they > > don't form any sort of persistent UAPI that we have to maintain? > > Sure. Note that we don't have any such comment in xfs either.. Yes, but that is buries inside the xfs code where we largely set our own rules. This, however, is generic code where people have a habit of arguing that tracepoints are stable API and they can never be changed because some random userspace application may have hard coded a dependency on it... Hence we need to be explicit here that this is diagnostic/debug code and anyone who tries to rely on it as a stable API gets to keep all the broken bits to themselves. Cheers, Dave. -- Dave Chinner david@fromorbit.com