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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 14D4DC433E1 for ; Sun, 12 Jul 2020 21:10:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0E732067D for ; Sun, 12 Jul 2020 21:10:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="O6F8mkCN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729397AbgGLVKu (ORCPT ); Sun, 12 Jul 2020 17:10:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37904 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729020AbgGLVKu (ORCPT ); Sun, 12 Jul 2020 17:10:50 -0400 Received: from mail-pf1-x444.google.com (mail-pf1-x444.google.com [IPv6:2607:f8b0:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 39E65C061794; Sun, 12 Jul 2020 14:10:50 -0700 (PDT) Received: by mail-pf1-x444.google.com with SMTP id u185so5071825pfu.1; Sun, 12 Jul 2020 14:10:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=lUm4cLOAP9oD2S5sJi8gYSXH2QfTVX1GOTo0+hkX9Vw=; b=O6F8mkCNKikIkJNPo8IyOR2P1aVobZP0JBcpPYikcOWdR66LKUkequBincy02tlLVy hcAxeAoGq+5TjhwWDKaRP716hbMChV0VTPnjGKpbAqNBXei8oDMKRk5YPID0Bvpgomxi TwPLqsGkWFsyaa1/nskgH15LdhQX0iy/0DsXFTrkfuccF6eqWxGbxlqiixcP+v9D0dpK qMapDHxkhgfPi0O62NVbKzUklImQDWs+FNxt0fMVCseWHXNZQWB/8obwHHuqD9N/pSBj o/4ynkYyIXaijTMou/mlVC3ievRIJtiIlRqp6Z4yaS68Of5WCao/vyl54IY1num1+f6X vPPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=lUm4cLOAP9oD2S5sJi8gYSXH2QfTVX1GOTo0+hkX9Vw=; b=d1sSnGdiqVmPsisNvSFxRGwACEq/7+EvweJDZT42Sn+a5CZszg/F2t7QgKj5D8zJ8N LgBL/QO3E9aHWgwLsg/GNlh4shpDiDz+bIG8XjyjvZ0ebEdz2gUH0w49D9iPxj87TzTb OM3uCPzeaFzeCauEa3KXMog41hCJCJF1WZQj4lp71oPn0v/cCdWtibn+hHGoTRR8YNN1 dTQwW5dBBWDSLSZ04gBFFbcYwVkvrmx2W5oVCb51Xvci5UyzUNV+2oXGHh3+G8WVhbgU QT+WX4wKU3t0hz/HyNAxNvQ5f9M01qfzcwq5lRs2a7MacRN+5NLc+7JR5gZcySEQ4o58 /nyQ== X-Gm-Message-State: AOAM532QDTifoxkq58QpvDQAkDfowFVLo0alGq5seRCgMTxV3/4PgfpW asJMB1mIzdIc6Up0Di2BBSY= X-Google-Smtp-Source: ABdhPJy3vL+y6+PJJgo91UvG6zi9x0U+Z/p1fmB+bUb9pJVVBrqWVjmhlbkhKbSU+d9auRivIZIbrA== X-Received: by 2002:a63:c603:: with SMTP id w3mr65777252pgg.284.1594588249757; Sun, 12 Jul 2020 14:10:49 -0700 (PDT) Received: from austin-fedora (IP-168-124.cs.nctu.edu.tw. [140.113.168.124]) by smtp.gmail.com with ESMTPSA id 204sm12275757pfx.3.2020.07.12.14.10.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Jul 2020 14:10:49 -0700 (PDT) Date: Mon, 13 Jul 2020 05:10:45 +0800 From: Austin Chang To: Matthew Wilcox Cc: dm-devel@redhat.com, Alasdair Kergon , Mike Snitzer , Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dm-cache: document zeroing metadata device step Message-ID: <20200712211045.GA332416@austin-fedora> References: <20200712194039.329035-1-austin880625@gmail.com> <20200712195932.GV12769@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200712195932.GV12769@casper.infradead.org> Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Sun, Jul 12, 2020 at 08:59:32PM +0100, Matthew Wilcox wrote: > On Mon, Jul 13, 2020 at 03:40:39AM +0800, Austin Chang wrote: > > + # When using dmsetup directly instead of volume manager like lvm2, > > + # the first 4k of the metadata device should be zeroed to indicate > > + # empty metadata. > > + dd if=/dev/zero of=/dev/mapper/metadata bs=4k conv=notrunc > > ... don't you need 'count=1' or you'll zero the entire device? Oops, I copied the command I just used since zeroing the whole metadata device didn't harm. But 'count=1' should match what I've just written. I will send a v2 patch later