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=-2.3 required=3.0 tests=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 81E45C11D2F for ; Mon, 24 Feb 2020 15:20:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5414B20838 for ; Mon, 24 Feb 2020 15:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727783AbgBXPUc (ORCPT ); Mon, 24 Feb 2020 10:20:32 -0500 Received: from mail-pf1-f195.google.com ([209.85.210.195]:39236 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727749AbgBXPUc (ORCPT ); Mon, 24 Feb 2020 10:20:32 -0500 Received: by mail-pf1-f195.google.com with SMTP id 84so5519946pfy.6 for ; Mon, 24 Feb 2020 07:20:30 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=WDCkjGM3fgtW4JPiMGZTVGouytm+nwZx0bWaIv/hYVo=; b=ba1CO+08Yhhcpyh+okjqYADOHwpX5aGw9iAzq525IZ2jqUKRKWt1dME5+6+e7SzWjD SQNLvsL5rOC2yfk/RjYI6DQnoijrq0k04z4P3kc83GSfU1W306HxAyQCfFGOKvL08s7n BvyZTPLIG5cpiI6Hz4i7VVwiO90tujF+gPdpr0U4x1B4mP6njlDhqY8K7li4aYQySNBe P4E6udQNQcgDDT5Gyql+1uBTOP1HQdfzZQ+Gn/esflxhcpKSlWSmmUL/CZ50v1EreVve XKLzVLNlUuubbtpWZi39bSVXWp1aQxsjtdfoWKZcIGgR5cUPPriSB8vDv73ug7RHcKHM O75g== X-Gm-Message-State: APjAAAXyANPioen0ba5x1bIbd16BCQlkEHWHFGoXKeqPnbzXhc8a3CGB tilImERZ7DYMANERHMr1yvo= X-Google-Smtp-Source: APXvYqzs7yXo0KmypHmS8gZLODgtXGsVmL4xyKacEAl9PCoYaSRdGD/huT9qE8pSy9z5ACK9o8/jPg== X-Received: by 2002:a63:e007:: with SMTP id e7mr52628098pgh.414.1582557630427; Mon, 24 Feb 2020 07:20:30 -0800 (PST) Received: from ?IPv6:2601:647:4000:d7:af99:b4cf:6b17:1075? ([2601:647:4000:d7:af99:b4cf:6b17:1075]) by smtp.gmail.com with ESMTPSA id 188sm13214549pgf.24.2020.02.24.07.20.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Feb 2020 07:20:29 -0800 (PST) Subject: Re: [PATCH v3 4/8] null_blk: Suppress an UBSAN complaint triggered when setting 'memory_backed' To: Chaitanya Kulkarni , Jens Axboe Cc: "linux-block@vger.kernel.org" , Christoph Hellwig , Christoph Hellwig , Ming Lei , Hannes Reinecke , Johannes Thumshirn References: <20200221032243.9708-1-bvanassche@acm.org> <20200221032243.9708-5-bvanassche@acm.org> From: Bart Van Assche Message-ID: <486df5d9-501c-b552-2f94-28d978f6bffb@acm.org> Date: Mon, 24 Feb 2020 07:20:27 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2/24/20 3:28 AM, Chaitanya Kulkarni wrote: > On 2/20/20 7:23 PM, Bart Van Assche wrote: >> Although it is not clear to me why UBSAN complains when 'memory_backed' >> is set, this patch suppresses the UBSAN complaint that is triggered when >> setting that configfs attribute. > > Is it due to "An uninitialized bool will have indeterminate value and using > an indeterminate value is undefined behavior." ? But where is the code that reads that boolean before it is set? I haven't found it. Hence the comment in the patch description. Bart.