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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 908ABC433E0 for ; Sun, 12 Jul 2020 19:59:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58F4A2067D for ; Sun, 12 Jul 2020 19:59:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="fqn0+zLg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729254AbgGLT7o (ORCPT ); Sun, 12 Jul 2020 15:59:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729249AbgGLT7n (ORCPT ); Sun, 12 Jul 2020 15:59:43 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 55758C061794; Sun, 12 Jul 2020 12:59:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=gAqVhOnFwwCoIwU0i8eoCwnixeJorp0605sJj8HaFrE=; b=fqn0+zLg0MWuNz1ruzQvb1SjSF JvoK9nbA2CPYK59PJQE6Jbf+EM4PA8TYlwkvQBcBc+HMzmlauqQagGIhFkmj6HFDdJZ8RqAyqAkce eh9cWyUkZZvBIG2xZsrR35q65hDDO3CSobrEe4dj/gnX7Ke2/ObLuIDEcVhe+ujRNGLeOWPQiW2kc zhgP7BhA8m1se0hYNeK2/6WMQumM3QKI3EDWyOs4glfbaR101UrwlX1izT4Zbf07ZmwDsJ/ZWJTde fLqgDYC/RkC+2Jt/XVpZaN2ltC+uL/Agdnl8cp43plRkuzwiAk9PuXi2u1ieWoT6BzDJZIxzdUC9N L8EfKrzg==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jui8K-0008N0-UE; Sun, 12 Jul 2020 19:59:33 +0000 Date: Sun, 12 Jul 2020 20:59:32 +0100 From: Matthew Wilcox To: Austin Chang 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: <20200712195932.GV12769@casper.infradead.org> References: <20200712194039.329035-1-austin880625@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200712194039.329035-1-austin880625@gmail.com> Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org 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? > dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \ > /dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0' > dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \ > -- > 2.26.2 >