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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 1FD10C43381 for ; Thu, 21 Mar 2019 17:48:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EDCC021902 for ; Thu, 21 Mar 2019 17:48:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728305AbfCURs3 (ORCPT ); Thu, 21 Mar 2019 13:48:29 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:43348 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728069AbfCURs3 (ORCPT ); Thu, 21 Mar 2019 13:48:29 -0400 Received: from callcc.thunk.org (guestnat-104-133-0-99.corp.google.com [104.133.0.99] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x2LHmCSG021729 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 21 Mar 2019 13:48:12 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 0B04D420AA8; Thu, 21 Mar 2019 13:48:12 -0400 (EDT) Date: Thu, 21 Mar 2019 13:48:11 -0400 From: "Theodore Ts'o" To: Lukas Czerner Cc: Ext4 Developers List , darrick.wong@oracle.com Subject: Re: [PATCH 8/9] e2scrub_all: refactor device probe loop Message-ID: <20190321174811.GF9434@mit.edu> References: <20190321020218.5154-1-tytso@mit.edu> <20190321020218.5154-8-tytso@mit.edu> <20190321102742.k2oos4epoj6fyjao@work> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190321102742.k2oos4epoj6fyjao@work> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu, Mar 21, 2019 at 11:27:42AM +0100, Lukas Czerner wrote: > > Snapshot of a thinspanshot is allowed though, so we might want to > include those. Not sure if it's wise to do it by default, but regardless > it's probably something for a separate change. Yeah, it's definitely a separate change. One potential design question is that for a thin volume, you can do both a thin or a think snapshot, and in some cases one might succeed while the other will fail. So do we make this choice be a parameter that we set in the config file, or do we try to see if there is sufficient spare freespace for a thick snapshot (and then do that), or a thin snapshot (and then do that) --- and which should use prefer? The other thing I'll note is that in order for us to tell whether something is a thin or thick LV, we're going to to need to ask lvs to return multiple parameters, so the optimization of using: for NAME in $(lvs -o lv_path --noheadings -S...) ; do ... done will no longer work. (Or we end up calling lvs a second time, which is less efficient.) Just curious --- do we know how commonly thin LV's are being used by customers of various distros? I assume enterprise distro users will be the most conservative, but how common is the uptake of thin LV's by Fedora and OpenSuSE users? - Ted