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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 413A3C63777 for ; Sun, 22 Nov 2020 22:36:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 97C3F20776 for ; Sun, 22 Nov 2020 22:36:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="it2DEm5q"; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="it2DEm5q" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 97C3F20776 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=HansenPartnership.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B80156B005D; Sun, 22 Nov 2020 17:36:08 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B09EA6B0070; Sun, 22 Nov 2020 17:36:08 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9D26E6B0071; Sun, 22 Nov 2020 17:36:08 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0163.hostedemail.com [216.40.44.163]) by kanga.kvack.org (Postfix) with ESMTP id 6856D6B005D for ; Sun, 22 Nov 2020 17:36:08 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 02C05180AD815 for ; Sun, 22 Nov 2020 22:36:08 +0000 (UTC) X-FDA: 77513513616.25.owl05_10151fc27360 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin25.hostedemail.com (Postfix) with ESMTP id CC2B41804E3B2 for ; Sun, 22 Nov 2020 22:36:07 +0000 (UTC) X-HE-Tag: owl05_10151fc27360 X-Filterd-Recvd-Size: 8036 Received: from bedivere.hansenpartnership.com (bedivere.hansenpartnership.com [96.44.175.130]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Sun, 22 Nov 2020 22:36:06 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 3EEFD12808AA; Sun, 22 Nov 2020 14:36:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1606084565; bh=y5Oo39UQGhMKIHztx5i9osM+IVUxOt/AInbXjgVEmOM=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References:From; b=it2DEm5qbX6tNKGabRZf0YZ7FJN256ppIXEFnMqNHN+XY9h76oTIzuZgEyEoREiKM yiP/0zNVKPNW1kWiLTindkrOQ7bXlSJOTVsRohihqSOzq1tvOmtHcybKKU2pQsn+gK kXbE7Tzelwaqt/71bFtBSSIQ6PZYHLF3M7J5PGe0= Received: from bedivere.hansenpartnership.com ([127.0.0.1]) by localhost (bedivere.hansenpartnership.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id YhaEdPXdRRpF; Sun, 22 Nov 2020 14:36:05 -0800 (PST) Received: from jarvis.int.hansenpartnership.com (unknown [IPv6:2601:600:8280:66d1::527]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by bedivere.hansenpartnership.com (Postfix) with ESMTPSA id B820412808A7; Sun, 22 Nov 2020 14:36:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1606084565; bh=y5Oo39UQGhMKIHztx5i9osM+IVUxOt/AInbXjgVEmOM=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References:From; b=it2DEm5qbX6tNKGabRZf0YZ7FJN256ppIXEFnMqNHN+XY9h76oTIzuZgEyEoREiKM yiP/0zNVKPNW1kWiLTindkrOQ7bXlSJOTVsRohihqSOzq1tvOmtHcybKKU2pQsn+gK kXbE7Tzelwaqt/71bFtBSSIQ6PZYHLF3M7J5PGe0= Message-ID: <1c7d7fde126bc0acf825766de64bf2f9b888f216.camel@HansenPartnership.com> Subject: Re: [PATCH 000/141] Fix fall-through warnings for Clang From: James Bottomley To: Miguel Ojeda Cc: Kees Cook , Jakub Kicinski , "Gustavo A. R. Silva" , linux-kernel , alsa-devel@alsa-project.org, amd-gfx@lists.freedesktop.org, bridge@lists.linux-foundation.org, ceph-devel@vger.kernel.org, cluster-devel@redhat.com, coreteam@netfilter.org, devel@driverdev.osuosl.org, dm-devel@redhat.com, drbd-dev@lists.linbit.com, dri-devel@lists.freedesktop.org, GR-everest-linux-l2@marvell.com, GR-Linux-NIC-Dev@marvell.com, intel-gfx@lists.freedesktop.org, intel-wired-lan@lists.osuosl.org, keyrings@vger.kernel.org, linux1394-devel@lists.sourceforge.net, linux-acpi@vger.kernel.org, linux-afs@lists.infradead.org, Linux ARM , linux-arm-msm@vger.kernel.org, linux-atm-general@lists.sourceforge.net, linux-block@vger.kernel.org, linux-can@vger.kernel.org, linux-cifs@vger.kernel.org, Linux Crypto Mailing List , linux-decnet-user@lists.sourceforge.net, Ext4 Developers List , linux-fbdev@vger.kernel.org, linux-geode@lists.infradead.org, linux-gpio@vger.kernel.org, linux-hams@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-i3c@lists.infradead.org, linux-ide@vger.kernel.org, linux-iio@vger.kernel.org, linux-input , linux-integrity@vger.kernel.org, linux-mediatek@lists.infradead.org, Linux Media Mailing List , linux-mmc@vger.kernel.org, Linux-MM , linux-mtd@lists.infradead.org, linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-sctp@vger.kernel.org, linux-security-module@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-usb@vger.kernel.org, linux-watchdog@vger.kernel.org, linux-wireless , Network Development , netfilter-devel@vger.kernel.org, nouveau@lists.freedesktop.org, op-tee@lists.trustedfirmware.org, oss-drivers@netronome.com, patches@opensource.cirrus.com, rds-devel@oss.oracle.com, reiserfs-devel@vger.kernel.org, samba-technical@lists.samba.org, selinux@vger.kernel.org, target-devel@vger.kernel.org, tipc-discussion@lists.sourceforge.net, usb-storage@lists.one-eyed-alien.net, virtualization@lists.linux-foundation.org, wcn36xx@lists.infradead.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , xen-devel@lists.xenproject.org, linux-hardening@vger.kernel.org, Nick Desaulniers , Nathan Chancellor , Miguel Ojeda , Joe Perches Date: Sun, 22 Nov 2020 14:36:00 -0800 In-Reply-To: References: <20201120105344.4345c14e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <202011201129.B13FDB3C@keescook> <20201120115142.292999b2@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <202011220816.8B6591A@keescook> <9b57fd4914b46f38d54087d75e072d6e947cb56d.camel@HansenPartnership.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.4 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, 2020-11-22 at 21:35 +0100, Miguel Ojeda wrote: > On Sun, Nov 22, 2020 at 7:22 PM James Bottomley > wrote: > > Well, it's a problem in an error leg, sure, but it's not a really > > compelling reason for a 141 patch series, is it? All that fixing > > this error will do is get the driver to print "oh dear there's a > > problem" under four more conditions than it previously did. > > > > We've been at this for three years now with nearly a thousand > > patches, firstly marking all the fall throughs with /* fall through > > */ and later changing it to fallthrough. At some point we do have > > to ask if the effort is commensurate with the protection > > afforded. Please tell me our reward for all this effort isn't a > > single missing error print. > > It isn't that much effort, isn't it? Well, it seems to be three years of someone's time plus the maintainer review time and series disruption of nearly a thousand patches. Let's be conservative and assume the producer worked about 30% on the series and it takes about 5-10 minutes per patch to review, merge and for others to rework existing series. So let's say it's cost a person year of a relatively junior engineer producing the patches and say 100h of review and application time. The latter is likely the big ticket item because it's what we have in least supply in the kernel (even though it's 20x vs the producer time). > Plus we need to take into account the future mistakes that it might > prevent, too. So even if there were zero problems found so far, it is > still a positive change. Well, the question I was asking is if it's worth the cost which I've tried to outline above. > I would agree if these changes were high risk, though; but they are > almost trivial. It's not about the risk of the changes it's about the cost of implementing them. Even if you discount the producer time (which someone gets to pay for, and if I were the engineering manager, I'd be unhappy about), the review/merge/rework time is pretty significant in exchange for six minor bug fixes. Fine, when a new compiler warning comes along it's certainly reasonable to see if we can benefit from it and the fact that the compiler people think it's worthwhile is enough evidence to assume this initially. But at some point you have to ask whether that assumption is supported by the evidence we've accumulated over the time we've been using it. And if the evidence doesn't support it perhaps it is time to stop the experiment. James