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 C433EC636D4 for ; Thu, 2 Feb 2023 16:51:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232356AbjBBQv2 (ORCPT ); Thu, 2 Feb 2023 11:51:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57242 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232344AbjBBQv0 (ORCPT ); Thu, 2 Feb 2023 11:51:26 -0500 Received: from mail-qt1-f171.google.com (mail-qt1-f171.google.com [209.85.160.171]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 024436D5FA for ; Thu, 2 Feb 2023 08:50:40 -0800 (PST) Received: by mail-qt1-f171.google.com with SMTP id cr22so2497668qtb.10 for ; Thu, 02 Feb 2023 08:50:39 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=1tztcBchRZ+ahQ+Rv8slGEZ3rlEReGoboay+wBElNpk=; b=m98LH0AV15WrlnFA8xo2kN/meupVPh8QKKgBdgQl/o50luIDPmi0Fb+hEfw6LmuV2y qmjy4JR9cM/WhCZ1wEwHSKojtexLY3MToupYpHDo/waocs3tUKOeXH3GRMoCjQc5lr+h SyzkKCDC0ga2W9HW0280Ljx6+bYnwJhpKUHvPUATztZ2SzBxeQuou+s05nBpY2SxgsXz NO2sIA5kgczX4q9BspwKVE4EKBaecj6QlFpvRtSdSzYOgMVOUV2q3DXLFfXlrweu3X7K QrS35tXzTRMdWMGwZxX01TF9WvTlIbwigKGNNmww3piQ/RIsM7/NPI4av5h/7IHdVj9p MNTA== X-Gm-Message-State: AO0yUKVPHq0m7uC2i/SLfFt7gSUbsY3q+G85bN1p9MH+lEzXhExCnoyT 1Kqx3Me6NKBGaG7Ud2XmYH4+Hsk+9KfSUVs= X-Google-Smtp-Source: AK7set+4Pyeb5ompgmUg0JYUv54bCb2ceknHgU0XW/UAy594tQAOCFstY5279x2+bA/W3Ae7xhvLGQ== X-Received: by 2002:a05:622a:1788:b0:3b8:2ea9:a093 with SMTP id s8-20020a05622a178800b003b82ea9a093mr13141578qtk.1.1675356639078; Thu, 02 Feb 2023 08:50:39 -0800 (PST) Received: from localhost (pool-68-160-166-30.bstnma.fios.verizon.net. [68.160.166.30]) by smtp.gmail.com with ESMTPSA id t9-20020a05620a034900b0071eddd3bebbsm31687qkm.81.2023.02.02.08.50.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Feb 2023 08:50:38 -0800 (PST) Date: Thu, 2 Feb 2023 11:50:37 -0500 From: Mike Snitzer To: Demi Marie Obenour Cc: Jens Axboe , Roger Pau =?iso-8859-1?Q?Monn=E9?= , Alasdair Kergon , Marek =?iso-8859-1?Q?Marczykowski-G=F3recki?= , Juergen Gross , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, dm-devel@redhat.com Subject: Re: [RFC PATCH 0/7] Allow race-free block device handling Message-ID: References: <20230126033358.1880-1-demi@invisiblethingslab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230126033358.1880-1-demi@invisiblethingslab.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 25 2023 at 10:33P -0500, Demi Marie Obenour wrote: > This work aims to allow userspace to create and destroy block devices > in a race-free and leak-free way, "race-free and leak-free way" implies there both races and leaks in existing code. You're making claims that are likely very specific to your Xen use-case. Please explain more carefully. > and to allow them to be exposed to > other Xen VMs via blkback without leaks or races. It’s marked as RFC > for a few reasons: > > - The code has been only lightly tested. It might be unstable or > insecure. > > - The DM_DEV_CREATE ioctl gains a new flag. Unknown flags were > previously ignored, so this could theoretically break buggy userspace > tools. Not seeing a reason that type of DM change is needed. If you feel strongly about it send a separate patch and we can discuss it. > - I have no idea if I got the block device reference counting and > locking correct. Your headers and justifcation for this line of work are really way too terse. Please take the time to clearly make the case for your changes in both the patch headers and code. Mike