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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable 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 27180C43387 for ; Fri, 21 Dec 2018 16:28:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EBC522087F for ; Fri, 21 Dec 2018 16:28:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388610AbeLUQ2b (ORCPT ); Fri, 21 Dec 2018 11:28:31 -0500 Received: from dmz-mailsec-scanner-6.mit.edu ([18.7.68.35]:55450 "EHLO dmz-mailsec-scanner-6.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731121AbeLUQ2b (ORCPT ); Fri, 21 Dec 2018 11:28:31 -0500 X-AuditID: 12074423-8c3ff700000053bc-94-5c1d14aa08b6 Received: from mailhub-auth-4.mit.edu ( [18.7.62.39]) (using TLS with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by dmz-mailsec-scanner-6.mit.edu (Symantec Messaging Gateway) with SMTP id 92.5D.21436.BA41D1C5; Fri, 21 Dec 2018 11:28:28 -0500 (EST) Received: from outgoing.mit.edu (OUTGOING-AUTH-1.MIT.EDU [18.9.28.11]) by mailhub-auth-4.mit.edu (8.14.7/8.9.2) with ESMTP id wBLGSOZ8023106; Fri, 21 Dec 2018 11:28:25 -0500 Received: from callcc.thunk.org (251.sub-174-192-22.myvzw.com [174.192.22.251]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id wBLGSFoJ012525 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 21 Dec 2018 11:28:19 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id 4458F7A45FA; Fri, 21 Dec 2018 11:28:13 -0500 (EST) Date: Fri, 21 Dec 2018 11:28:13 -0500 From: "Theodore Y. Ts'o" To: Matthew Wilcox Cc: Christoph Hellwig , Dave Chinner , "Darrick J. Wong" , Eric Biggers , linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, Jaegeuk Kim , Victor Hsieh , Chandan Rajendra , Linus Torvalds Subject: Re: [PATCH v2 01/12] fs-verity: add a documentation file Message-ID: <20181221162813.GB26547@mit.edu> Mail-Followup-To: "Theodore Y. Ts'o" , Matthew Wilcox , Christoph Hellwig , Dave Chinner , "Darrick J. Wong" , Eric Biggers , linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, Jaegeuk Kim , Victor Hsieh , Chandan Rajendra , Linus Torvalds References: <20181219071420.GC2628@infradead.org> <20181219021953.GD31274@dastard> <20181219193005.GB6889@mit.edu> <20181219213552.GO6311@dastard> <20181220220158.GC2360@mit.edu> <20181221070447.GA21687@infradead.org> <20181221154714.GA26547@mit.edu> <20181221155354.GC10600@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181221155354.GC10600@bombadil.infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Brightmail-Tracker: H4sIAAAAAAAAA02Se0gUURTGuzPj7Lg4cl01b6sGbUVhaRkhE2gvCqciKKjAEmp0J3dxd7WZ 1dQKLEN0tbCobBddNo0etlq5Yj4rHy2+CEoxiawwLZTMQjRFi3bWfPx3zvf7vnPu5V4KV4x6 KCmtwcgLBk6nIuWEQrZ9XajdLzh2c5vDh8m/0eTB9I8982CqnB8BU94wizOdBSUYM/jYgjNm 6weSeVsSzYxYJwmmobGdYNpeO2VMd10RyXwymXBm4OqojGl1tJLMzFQRuROyHSWItVWmsI4H IWxlWS7Jtt2eIdjPzQ6CrbeNY+yvofcEe/lFL8mOV648JD8uj1TzOm0qL2zafkqu+VBbiyd/ k6X9vFUFMsFd0gQ8KQS3otKuEZkJyCkFtGPImfcLn2ueAvSywvm/eYOhm333MSmigAIae1cN pJqAa9GrpotunYTrkX3oD2ECFOXnqr9XbZGyOOwjULY11+33hbtQ6cAPt5+GG1HpYKF7AQ1/ E2hiuoyc21aDoczOO/9dPqjdPEhINQ5DUN/fYUzagMNAdP8vJcmeMBL9aOyRSbI/XIPGbbAA KCxLwpYlYcti2AbwMhCs1meE6jmtTuTjQ8V4zmDghdCIML3WGMarUyqB+1X3rK4Bw1cPNANI AZUXXTAZFKvw4FLFdH0zWEFhKn86b9olecclqdM1nKg5KaToeLEZIApX+dE5US5Gq7n0DF5I mkeBFKEKoGf9vpxQwATOyCfyfDIvzNMgilIh2uYbHKvwEfgEPu20VmdcxBjlKQ33cg2vkjy0 mMzpRW3CHO8Aq5QB9F0JQAloUgwLWemXVrxcPjMCAlxX8aVJyeXl+sML6RHXYMw1WL5bOrVo 5BaRMhOkhx9uLIRO9dfi6IHuEPOOn2lwmblvgxUVrnMUpWYph6YuyCJawi+dLbXvtxzZpiSO FMRvCeqP6bL51JzPE0rq4sIK84ee4r6dx1ZavI+Zz6X1nBGvd1w52JsdlWOrns1s2TeRW/GI jdmbNT6QfPLJquv3jibW24utD0+UP7/Wr1IRooYLD8EFkfsHYox4f4ADAAA= Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Fri, Dec 21, 2018 at 07:53:54AM -0800, Matthew Wilcox wrote: > In contrast to "we'll just fix it up later" (which usually applies > to in-kernel interfaces), we have a policy of not breaking userspace, > so accepting this interface means setting it in stone. We should get > it right. I'm not convinced it's a "fix", but my point is that if later on you want to add extra complexity transforming ioctl(fd, FS_IOC_ENABLE_VERITY); so it does the equivalent of ioctl(fd, FS_IOC_ENABLE_VERITY_NOW_WITH_EXTRA_USELESS_COMPLEXITY, fd, sizeof_data, sizeof_verity_data); it adds essentially no complexity to provide this backwards compatibility. But if we need to implement FS_IOC_ENABLE_VERITY_NOW_WITH_EXTRA_USELESS_COMPLEXITY *now*, we gain nothing, other than pushing back when fsverity lands upstream. We'd have to provide that backwards compatibility interface anyway, since there are a lot of users for that existing interface. So why? - Ted