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 30010C77B7C for ; Fri, 26 May 2023 10:26:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243059AbjEZK0k (ORCPT ); Fri, 26 May 2023 06:26:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35920 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236835AbjEZK0i (ORCPT ); Fri, 26 May 2023 06:26:38 -0400 Received: from out30-99.freemail.mail.aliyun.com (out30-99.freemail.mail.aliyun.com [115.124.30.99]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 38584FB for ; Fri, 26 May 2023 03:26:37 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R391e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046051;MF=durui@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VjW4Oiz_1685096793; Received: from localhost(mailfrom:durui@linux.alibaba.com fp:SMTPD_---0VjW4Oiz_1685096793) by smtp.aliyun-inc.com; Fri, 26 May 2023 18:26:34 +0800 From: Du Rui To: alexl@redhat.com Cc: agk@redhat.com, dm-devel@redhat.com, durui@linux.alibaba.com, gscrivan@redhat.com, linux-kernel@vger.kernel.org, snitzer@kernel.org Subject: Re: Re: dm overlaybd: targets mapping OverlayBD image Date: Fri, 26 May 2023 18:26:33 +0800 Message-Id: <20230526102633.31160-1-durui@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Alexander, > all the lvm volume changes and mounts during runtime caused > weird behaviour (especially at scale) that was painful to manage (just > search the docker issue tracker for devmapper backend). In the end > everyone moved to a filesystem based implementation (overlayfs based). Yes, we had exactly the same experience. This is another reason why this proposal is for dm and lvm, not for container. (BTW, we are using TCMU and ublk for overlaybd in production. They are awesome.) > This solution doesn't even allow page cache sharing between shared > layers (like current containers do), much less between independent > layers. Page cache sharing can be realized with DAX support of the dm targets (and the inner file system), together with virtual pmem device backend. > Erofs already has some block-level support for container images It is interesting. Erofs runs insider a block device in the first place, like what many file systems do. But do you konw why it implements another "some block-level support" by itself? > And this new approach doesn't help No. It is intended for dm and lvm.