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 9B275E92FD2 for ; Thu, 5 Oct 2023 23:08:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229457AbjJEXIO (ORCPT ); Thu, 5 Oct 2023 19:08:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39728 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229584AbjJEXFw (ORCPT ); Thu, 5 Oct 2023 19:05:52 -0400 Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F060C18D; Thu, 5 Oct 2023 15:58:42 -0700 (PDT) Received: by mail-pl1-f169.google.com with SMTP id d9443c01a7336-1c5c91bece9so12667845ad.3; Thu, 05 Oct 2023 15:58:42 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696546722; x=1697151522; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Ltrto+rjiXQu6CZ+tQzK6opfBYwCjT8QDYR8jfh7uis=; b=O7DASNSznlTd5ejToG7zZxT0IN65h5T8Uh1E7nOD4KR3FSTFiKp5uU0Klez9Eofr9S RUwEZRW+TnRzEJBgkjn52VWF4fl1wydVjaYeJtI5wZq8CLoY4/CwtmN2r5niieEJ7FVK Oa48bzGPTGd9Ir8SPA21xlelOjhxI1pu0NkrEiWXcdNm9Ad5CNjTx0qFzQ1XQITVFL4O +gvlsu5qz8Zln17rfS9W7BdUol9y20ikB2sMNlqa75ZHYXInhp9t6+xUa5uD+HhF+d/5 UlVTcsTutcDLmNFcm9eh731zopuJ+c9I90dcdCvUNTZ9zdIdtRWnbRE7o41jgsK8h0nb fbiw== X-Gm-Message-State: AOJu0Yzi0rLi9lue2JnwHKT1HEOiqXI/mvVVO6es2brMnUzeCewWBJJ1 feaVLmWZO3DMDF20j/hzyo8= X-Google-Smtp-Source: AGHT+IG0/9Wn5G/tnzM5vE5E/JIG1ER4pe53NdB/BX3Y8VlltjOu9i9A0D7Ui0Qfz98C4QopBOrp7w== X-Received: by 2002:a17:902:6ac4:b0:1c6:d34:5279 with SMTP id i4-20020a1709026ac400b001c60d345279mr6265144plt.13.1696546722102; Thu, 05 Oct 2023 15:58:42 -0700 (PDT) Received: from [192.168.51.14] (c-73-231-117-72.hsd1.ca.comcast.net. [73.231.117.72]) by smtp.gmail.com with ESMTPSA id 6-20020a170902c24600b001b89a6164desm2316513plg.118.2023.10.05.15.58.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Oct 2023 15:58:41 -0700 (PDT) Message-ID: Date: Thu, 5 Oct 2023 15:58:38 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 10/21] block: Add fops atomic write support Content-Language: en-US To: Dave Chinner Cc: "Martin K. Petersen" , John Garry , axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, jejb@linux.ibm.com, djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, chandan.babu@oracle.com, dchinner@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com, linux-api@vger.kernel.org References: <20230929102726.2985188-11-john.g.garry@oracle.com> <17ee1669-5830-4ead-888d-a6a4624b638a@acm.org> <5d26fa3b-ec34-bc39-ecfe-4616a04977ca@oracle.com> <34c08488-a288-45f9-a28f-a514a408541d@acm.org> From: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 10/5/23 15:36, Dave Chinner wrote: > $ lspci |grep -i nvme > 03:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981/PM983 > 06:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981/PM983 > $ cat /sys/block/nvme*n1/queue/write_cache > write back > write back > $ > > That they have volatile writeback caches.... It seems like what I wrote has been misunderstood completely. With "handling a power failure cleanly" I meant that power cycling a block device does not result in read errors nor in reading data that has never been written. Although it is hard to find information about this topic, here is what I found online: * About certain SSDs with power loss protection: https://us.transcend-info.com/embedded/technology/power-loss-protection-plp * About another class of SSDs with power loss protection: https://www.kingston.com/en/blog/servers-and-data-centers/ssd-power-loss-protection * About yet another class of SSDs with power loss protection: https://phisonblog.com/avoiding-ssd-data-loss-with-phisons-power-loss-protection-2/ So far I haven't found any information about hard disks and power failure handling. What I found is that most current hard disks protect data with ECC. The ECC mechanism should provide good protection against reading data that has never been written. If a power failure occurs while a hard disk is writing a physical block, can this result in a read error after power is restored? If so, is this behavior allowed by storage standards? Bart.