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[2620:137:e000::1:20]) by mx.google.com with ESMTP id y17-20020aa793d1000000b00640f7f287dcsi3674204pff.174.2023.05.26.20.30.30; Fri, 26 May 2023 20:30:45 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237518AbjE0DNa (ORCPT + 99 others); Fri, 26 May 2023 23:13:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54294 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229691AbjE0DN0 (ORCPT ); Fri, 26 May 2023 23:13:26 -0400 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53BCDEA for ; Fri, 26 May 2023 20:13:24 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R121e4;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=8;SR=0;TI=SMTPD_---0VjYXb68_1685157200; Received: from localhost(mailfrom:durui@linux.alibaba.com fp:SMTPD_---0VjYXb68_1685157200) by smtp.aliyun-inc.com; Sat, 27 May 2023 11:13:20 +0800 From: Du Rui To: hsiangkao@linux.alibaba.com Cc: agk@redhat.com, alexl@redhat.com, dm-devel@redhat.com, durui@linux.alibaba.com, gscrivan@redhat.com, linux-kernel@vger.kernel.org, snitzer@kernel.org Subject: Re: dm overlaybd: targets mapping OverlayBD image Date: Sat, 27 May 2023 11:13:19 +0800 Message-Id: <20230527031319.92200-1-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 X-Spam-Status: No, score=-9.9 required=5.0 tests=BAYES_00, ENV_AND_HDR_SPF_MATCH,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE,UNPARSEABLE_RELAY,USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Block drivers has nothing to do on filesystem page cache stuffs, also > currently your approach has nothing to do with pmem stuffs (If you must > mention "DAX" to proposal your "page cache sharing", please _here_ > write down your detailed design first and explain how it could work to > ours if you really want to do.) We have already done experiments (by virtio pmem), to make virtual PMEM device in QEMU, make guest vm sharing only one memory mapping on host, with filesystem that supports DAX. In guest vm, fs keeps no page cache, maybe "sharing pagecache" is not such accurate description, but sharing memory pages on host can do prevent making duplicated pagecache pages in VMs. Please make sure that you have already understood that dm-overlaybd are for GENERIC purpose. It is NOT a special design for container, and have nothing related to filesystem implementations.