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[2620:137:e000::1:20]) by mx.google.com with ESMTP id l190-20020a6225c7000000b0063b1bfa94dasi2714035pfl.323.2023.04.13.17.26.24; Thu, 13 Apr 2023 17:26:41 -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; dkim=pass header.i=@gmail.com header.s=20221208 header.b=oYNX4rkx; 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=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230034AbjDNAXT (ORCPT + 99 others); Thu, 13 Apr 2023 20:23:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229469AbjDNAXR (ORCPT ); Thu, 13 Apr 2023 20:23:17 -0400 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29DB9E4E for ; Thu, 13 Apr 2023 17:23:17 -0700 (PDT) Received: by mail-pl1-x62c.google.com with SMTP id d9443c01a7336-1a66895aafdso1440635ad.0 for ; Thu, 13 Apr 2023 17:23:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1681431796; x=1684023796; h=content-disposition:mime-version:message-id:subject:to:from:date :from:to:cc:subject:date:message-id:reply-to; bh=tPlT04Li3mmLsWP0TB9ZFLKkoXnJzg7ZzLsPJrNqauE=; b=oYNX4rkxSfvVJTrd9yYASBFZuipEg8Ilgqpu2LdnLTRrN4dxhltuJvJJmLpTltMtGR nfwT/kd2s/+vefkL1+aKhPlHMVnqQuPp4eX/+zomYhYQfftVrL/IeSBaPnwNxeYbUUDA 7vwxUmNRuLRiLEuQdfaE5Gsh0gU52N4p7Q6hZKqMPfRM/Zv/XBw87MSxIwi7gG/FJpmU RkpMDDw6g7M/5JgE0ZkaaRpdUFNlcbwymH7m+FTXrRmPNiRvPfxvEyv1QgE2XDu60GKe E7sN+eRkp8vYnB/4hK6ncQhZ9/d41olrp5c6FyMGscw39MSUb7ctinIXpAU69DO7C780 Kfsw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681431796; x=1684023796; h=content-disposition:mime-version:message-id:subject:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=tPlT04Li3mmLsWP0TB9ZFLKkoXnJzg7ZzLsPJrNqauE=; b=LOg7cXNL+vZ9N4PcmLX5TNWkTgqth20Dk5bqkRVX33aDiTSn54Q9LudBGoapVMkncG +Wrpcy3TM3DAWFKP7oyxdkfDwd0yYlQTrHnmW73Icmx/Zv5bmOJ9LypzDmlbBPtTnXaD l49/0MTvQJmNJtt76WkJtQH1NBqVts+bdOGBno6YsvuAGmtugPBv1LVzKncbAT/6yW4y TS8DmsbsZbSATMsM8iTB7tCmh8xAsYZdUogOf7a5KE84MkQLML6z31k/BdG5RdtV4Ay5 J08RUPYd61bUIZIzXbMkIxoMor55U9I1RaARLbeBk8CT+Cz4OWcPiUU+RQsxJv0KYUI7 jGLA== X-Gm-Message-State: AAQBX9cXBskKys9bUVihjDzqy45t/1w5oBj0k024npRLuUc4+iSRi0TC CufZJJS2BLGC4vKFEO5k9j93qaLmrOE= X-Received: by 2002:a17:902:e746:b0:19a:7217:32af with SMTP id p6-20020a170902e74600b0019a721732afmr721994plf.5.1681431796043; Thu, 13 Apr 2023 17:23:16 -0700 (PDT) Received: from hoboy.vegasvil.org ([2601:640:8200:33:e2d5:5eff:fea5:802f]) by smtp.gmail.com with ESMTPSA id q17-20020a170902789100b001a1ca6dc38csm2001920pll.118.2023.04.13.17.23.15 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Apr 2023 17:23:15 -0700 (PDT) Date: Thu, 13 Apr 2023 17:23:13 -0700 From: Richard Cochran To: linux-kernel@vger.kernel.org Subject: Weirdness with bind mounts and moving files from tmpfs Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS 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 Dear list, If a file is copied from tmpfs onto a bind mount, the contents update as expected. However if a file is _moved_ from tmpfs onto a bind mount, the old content persists. For example, my PC has a tmpfs on /run: # findmnt /run TARGET SOURCE FSTYPE OPTIONS /run tmpfs tmpfs rw,nosuid,nodev,noexec,relatime,size=5737612k,mode=755,inode64 Set up a bind mounted file... # touch /opt/file # echo one > /home/file # mount -o bind /home/file /opt/file # cat /opt/file one Coping a file onto the bind mount via the tmpfs on /run yields... # echo two > /run/file # cp /run/file /home/file # cat /opt/file two So far, so good. Now do the same, but with 'mv' instead of 'cp'... # echo three > /run/file # mv /run/file /home/file # cat /opt/file two At this point, the contents of /opt/file are stuck forever with "two"... # echo three > /run/file # cp /run/file /home/file # cat /opt/file two # echo three > /home/file # cat /opt/file two What is going on here? Is this a bug or a feature? Thanks, Richard