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 0716CC433EF for ; Tue, 24 May 2022 04:53:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233425AbiEXExl (ORCPT ); Tue, 24 May 2022 00:53:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229506AbiEXExg (ORCPT ); Tue, 24 May 2022 00:53:36 -0400 Received: from out01.mta.xmission.com (out01.mta.xmission.com [166.70.13.231]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 728BE62A1D for ; Mon, 23 May 2022 21:53:35 -0700 (PDT) Received: from in02.mta.xmission.com ([166.70.13.52]:54206) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1ntMY1-00Bvid-66; Mon, 23 May 2022 22:53:33 -0600 Received: from ip68-227-174-4.om.om.cox.net ([68.227.174.4]:39174 helo=email.froward.int.ebiederm.org.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1ntMY0-0071W8-5W; Mon, 23 May 2022 22:53:32 -0600 From: "Eric W. Biederman" To: Jens Axboe Cc: "Jason A. Donenfeld" , Al Viro , Theodore Ts'o , Christoph Hellwig , LKML References: <20220520094459.116240-1-Jason@zx2c4.com> <7e78d6a7-1cc3-2408-fe91-0329f5020e77@kernel.dk> <69bd18e6-d216-dfb3-201b-f6a285deb0e7@kernel.dk> <247ac77e-15e0-8612-2507-7bbac80af824@kernel.dk> Date: Mon, 23 May 2022 23:52:57 -0500 In-Reply-To: <247ac77e-15e0-8612-2507-7bbac80af824@kernel.dk> (Jens Axboe's message of "Fri, 20 May 2022 10:41:12 -0600") Message-ID: <87h75fwmza.fsf@email.froward.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1ntMY0-0071W8-5W;;;mid=<87h75fwmza.fsf@email.froward.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.174.4;;;frm=ebiederm@xmission.com;;;spf=softfail X-XM-AID: U2FsdGVkX18cLxvV7JryUCAMk8wwYfAC4T/wbsCw3uA= X-SA-Exim-Connect-IP: 68.227.174.4 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v4 0/3] random: convert to using iters, for Al Viro X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe writes: > On 5/20/22 10:39 AM, Jason A. Donenfeld wrote: >> Hi Jens, >> >> On Fri, May 20, 2022 at 10:24:36AM -0600, Jens Axboe wrote: >>> On 5/20/22 10:15 AM, Al Viro wrote: >>>> IIRC, Linus' position at the time had been along the lines of >>>> "splice is not so good ABI anyway, so let's do it and fix up >>>> the places that do get real-world complaints once such appear". >>>> So /dev/urandom is one such place... >>> >>> That's what Christoph said too. Honestly that's a very odd way to >>> attempt to justify breakage like this, even if it is tempting to >>> facilitate the set_fs() removal. But then be honest about it and say >>> it like it is, rather than some hand wavy explanation that frankly >>> doesn't make any sense. >>> >>> The referenced change doesn't change the splice ABI at all, hence the >>> justification seems very random to me. It kept what we already have, >>> except we randomly break some use cases. >> >> It looks like Al is right in the sense that Linus must certainly be >> aware of the breakage. He fixed tty in 9bb48c82aced ("tty: implement >> write_iter"). > > I don't think anyone is disputing that, but I also know that Linus wants > these fixed up as they are discovered. And I agree with him on that, > even if I disagree on the process to get there as it introduced > frivolous breakage... I believe the hypothesis at the time was that on many of these interfaces splice is not used on them so it did matter. With everything being fixed in the places the hypothesis turned out to be wrong. The rule is no regressions, not bug comparability forever. This allows things like removing a.out binary support, and many other things that are just dead code these days. Sometimes the only way to discover what has users is to remove support and wait a while and see if anyone complains. Sometimes doing that is worth it, other times it is not. My general sense is that there have been few enough reports that users who care about splice support have been few and far between. Which suggests the hypothesis was not an unreasonable one when Linus made it. The truly unfortunate part is that no one knew enough about these users to be able to step up and say that they care about splice on those interfaces at the start of this process. Eric