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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 11C0CC433DB for ; Thu, 11 Feb 2021 19:02:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B5A1064DE3 for ; Thu, 11 Feb 2021 19:02:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231249AbhBKSza (ORCPT ); Thu, 11 Feb 2021 13:55:30 -0500 Received: from mx2.suse.de ([195.135.220.15]:57594 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230493AbhBKSzP (ORCPT ); Thu, 11 Feb 2021 13:55:15 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 14A0EAD57; Thu, 11 Feb 2021 18:54:29 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 10DDFDA6E9; Thu, 11 Feb 2021 19:52:35 +0100 (CET) Date: Thu, 11 Feb 2021 19:52:34 +0100 From: David Sterba To: Ira Weiny Cc: Matthew Wilcox , Christoph Hellwig , Andrew Morton , clm@fb.com, josef@toxicpanda.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH V2 4/8] mm/highmem: Add VM_BUG_ON() to mem*_page() calls Message-ID: <20210211185234.GG1993@suse.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Ira Weiny , Matthew Wilcox , Christoph Hellwig , Andrew Morton , clm@fb.com, josef@toxicpanda.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20210210062221.3023586-1-ira.weiny@intel.com> <20210210062221.3023586-5-ira.weiny@intel.com> <20210210125502.GD2111784@infradead.org> <20210210162901.GB3014244@iweiny-DESK2.sc.intel.com> <20210210185606.GF308988@casper.infradead.org> <20210210212228.GF3014244@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210210212228.GF3014244@iweiny-DESK2.sc.intel.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Feb 10, 2021 at 01:22:28PM -0800, Ira Weiny wrote: > On Wed, Feb 10, 2021 at 06:56:06PM +0000, Matthew Wilcox wrote: > > On Wed, Feb 10, 2021 at 08:29:01AM -0800, Ira Weiny wrote: > > > And I thought it was a good idea. Any file system development should have > > > tests with DEBUG_VM which should cover Matthew's concern while not having the > > > overhead in production. Seemed like a decent compromise? > > > > Why do you think these paths are only used during file system development? > > I can't guarantee it but right now most of the conversions I have worked on are > in FS's. > > > They're definitely used by networking, by device drivers of all kinds > > and they're probably even used by the graphics system. > > > > While developers *should* turn on DEBUG_VM during development, a > > shockingly high percentage don't even turn on lockdep. > > Honestly, I don't feel strongly enough to argue it. I checked my devel config and I don't have DEBUG_VM enabled, while I have a bunch of other debugging options related to locking or other fine-grained sanity checks. The help text is not very specific what exactly is being checked other that it hurts performance, so I read it as that it's for MM developers that change the MM code, while in filesystem we use the APIs. However, for the this patchset I'll turn it on all testing instances of course. > Andrew? David? David this is going through your tree so would you feel more > comfortable with 1 or the other? I think it's a question for MM people, for now I assume it's supposed to be VM_BUG_ON.