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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 C0729C18E5B for ; Wed, 25 Mar 2020 08:52:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F146206F8 for ; Wed, 25 Mar 2020 08:52:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727339AbgCYIwj (ORCPT ); Wed, 25 Mar 2020 04:52:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:35304 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727372AbgCYIwj (ORCPT ); Wed, 25 Mar 2020 04:52:39 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 18AC2B11F; Wed, 25 Mar 2020 08:52:37 +0000 (UTC) Subject: Re: [RFC PATCH v2 3/3] dm zoned: add regular device info to metadata To: Damien Le Moal , Bob Liu , "dm-devel@redhat.com" Cc: "linux-block@vger.kernel.org" , Dmitry Fomichev References: <20200324110255.8385-1-bob.liu@oracle.com> <20200324110255.8385-4-bob.liu@oracle.com> <812da9e9-cfd2-ea24-60cb-4af48f476079@suse.de> From: Hannes Reinecke Message-ID: <0bd2daa1-abbf-681d-405c-f7e4aecd577c@suse.de> Date: Wed, 25 Mar 2020 09:52:33 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 3/25/20 9:02 AM, Damien Le Moal wrote: > On 2020/03/25 15:47, Hannes Reinecke wrote: >> On 3/25/20 7:29 AM, Damien Le Moal wrote: >>> On 2020/03/24 20:04, Bob Liu wrote: >>>> This patch implemented metadata support for regular device by: >>>> - Emulated zone information for regular device. >>>> - Store metadata at the beginning of regular device. >>>> >>>> | --- zoned device --- | -- regular device || >>>> ^ ^ >>>> | |Metadata >>>> zone 0 >>>> >>>> Signed-off-by: Bob Liu >>>> --- >>>> drivers/md/dm-zoned-metadata.c | 135 +++++++++++++++++++++++++++++++---------- >>>> drivers/md/dm-zoned-target.c | 6 +- >>>> drivers/md/dm-zoned.h | 3 +- >>>> 3 files changed, 108 insertions(+), 36 deletions(-) >>>> >> Having thought about it some more, I think we cannot continue with this >> 'simple' approach. >> The immediate problem is that we lie about the disk size; clearly the >> metadata cannot be used for regular data, yet we expose a target device >> with the full size of the underlying device. >> Making me wonder if anybody ever tested a disk-full scenario... > > Current dm-zoned does not do that... What is exposed as target capacity is > number of chunks * zone size, with the number of chunks being number of zones > minus metadata zones minus number of zones reserved for reclaim. And I did test > disk full scenario (when performance goes to the trash bin because reclaim > struggles...) > Thing is, the second number for the dmsetup target line is _supposed_ to be the target size. Which clearly is wrong here. I must admit I'm not sure what device-mapper will do with a target definition which is larger than the resulting target device ... Mike should know, but it's definitely awkward. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer