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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 C1534C43331 for ; Fri, 6 Sep 2019 09:27:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 99A492084F for ; Fri, 6 Sep 2019 09:27:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="ngA7m4GT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392899AbfIFJ13 (ORCPT ); Fri, 6 Sep 2019 05:27:29 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:53822 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726073AbfIFJ13 (ORCPT ); Fri, 6 Sep 2019 05:27:29 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x869O48i004154; Fri, 6 Sep 2019 09:27:03 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2019-08-05; bh=4vtA4TrCDSrAfXnJgvttGzQEl5OpH712NFRkuSuYZdE=; b=ngA7m4GTNdTa1pnsnQDclopna/1uO0ddWAHWoF4VF+9l+kkIpcVMbl6V2vHrlrzsn2aw JRMo3Wq5NZdFONpNs9CYyQmeyTkZsSgI9UcjbqgLDRLC+QfN3z2KwXz/erF+au2q3UWE oKPeqg6GCn3ITUsXIT+PWjgGXgaBi2I84gNJMdslVTKRYDLAeyKxpPD+JsT3Zh6zNdlP L6WcguEJzJsYL8rzIsVZYW13zGjaUTD0jZjgrJJ5qMpA4N3NvDa6W2lRSFb517Iivaw4 e7BBDPX3cKuVFGY5v8MLaB1qXpHN+9I1EkENGViJmucFvp1Bd5UtrAvcUj82bR5/6PwB cw== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2130.oracle.com with ESMTP id 2uumbp87tt-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 06 Sep 2019 09:27:03 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x869NTgG105179; Fri, 6 Sep 2019 09:27:02 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3020.oracle.com with ESMTP id 2uud7pb8hy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 06 Sep 2019 09:27:02 +0000 Received: from abhmp0002.oracle.com (abhmp0002.oracle.com [141.146.116.8]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x869R1WT006760; Fri, 6 Sep 2019 09:27:01 GMT Received: from [10.186.51.128] (/10.186.51.128) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 06 Sep 2019 02:27:00 -0700 Subject: Re: [PATCH] btrfs-progs: drop unique uuid test for btrfstune -M To: Nikolay Borisov , linux-btrfs@vger.kernel.org References: <20190906005025.2678-1-anand.jain@oracle.com> From: Anand Jain Message-ID: <232bccd3-3623-8ee9-18db-98edf7cd2e25@oracle.com> Date: Fri, 6 Sep 2019 17:27:00 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9371 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1909060098 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9371 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1909060098 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org > This is intended. Otherwise it's an open avenue for the user to shoot > themselves in the foot. I don't understand how? > If you know what you are doing and are > absolutely sure the original fs is no longer present > - then just flush > libblkid cache and you'll be able to set the FSID back to the original one. > No no its not about the stale cache holding the original fsid. The use case is - a golden copy of the bootable OS image is being used and shares the same fsid on multiple hosts. Now if you want to mount another copy it for some changes, you need to btrfstune -m on the copy. And later if you want to boot it successfully, it needs its original fsid back. HTH, Anand