From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 33AD949B202 for ; Fri, 11 Sep 2026 16:07:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789142859; cv=none; b=SiYZoPF1VGNkFkMa+XTXJRCTcEb0GkFgRBb8zbRl37S1xBZDfH/asv3hbGtELSP5B+o+1AhO23EIhJW+bT2ihOErqBpIJYRDWWBIFVBXl8PTGkxJcMWGnUJS31eka0h/iMZRsRexqO1BJ4tpe449olXTozk1pcmnUdn+GQKk0t4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789142859; c=relaxed/simple; bh=dsSez3iIkwjff/1EbAtSPDeoRvW0W4YMmEGhRiZaz6w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=NMrgy766EKjT/cYVAfEuAiEmem9viG0lS/zTOGKY/6jh74X8GfIsuGHvJnPcRFm/nDTRwDDHCfI0KZLYq7upz1o9j6TDJsBDS+lKUijJZm/lwUrgNEGFd4Qw9h+x8zaqNYtlZzqe13wTDXQK4W3+pTUMRlFgFEPNs2p2Zei1VzQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=P9z3tej0; arc=none smtp.client-ip=192.198.163.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="P9z3tej0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1789142858; x=1820678858; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=dsSez3iIkwjff/1EbAtSPDeoRvW0W4YMmEGhRiZaz6w=; b=P9z3tej0IQVZj+2CgBsQ949Zl46P6lOSGupAAEBchsmypMOVpPv17TWy Y8H/Z4hvZK2VxG+P4jzLESbE3kYwvMVPMu+1jQ6nyECrnHgrkoEJfIIlG ob1KNEcChnNuyjA1H4sFlvcrc7k7Of5DQ5IfVgi1CFBRylPRe8I/ZgEYJ RKhpDCTudBEAmQCN6m5iXPVPh6KPZm1hWsr0qWlkRx2PzyC0lyolSdWrP NM3CVSgQf/MgQ/zPXnsDZjKw5pX0fbZGncYdtnGg1uwspUH7xa9rQ1v/4 ZRyvFBIdxTpiN2JN9G2+AUljWB2vLru2EkWBtHNOExnyEjv5ievY+3FSV Q==; X-CSE-ConnectionGUID: klid+Uv9T5ScwPQzVDk8Pw== X-CSE-MsgGUID: E9AxugUWTDW42qQ62xJfbA== X-URL-LookUp-ScanningError: 1 X-IronPort-AV: E=McAfee;i="6800,10657,11902"; a="89480508" X-IronPort-AV: E=Sophos;i="6.27,97,1787036400"; d="p7s'346?scan'346,208,346";a="89480508" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2026 09:07:37 -0700 X-CSE-ConnectionGUID: 0V8chWv5QaS97ofS8FK72A== X-CSE-MsgGUID: bHY92lSeRPyzpaIzzNO3WQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,97,1787036400"; d="p7s'346?scan'346,208,346";a="270582591" Received: from tjmaciei-mobl5.jf.intel.com (HELO tjmaciei-mobl5.localnet) ([10.24.81.190]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2026 09:07:37 -0700 From: Thiago Macieira To: Dave Hansen , Anand Suveer Jain Cc: sashal@kernel.org, linux-btrfs@vger.kernel.org, David Woodhouse , David Sterba Subject: Re: [PATCH 1/3] btrfs: derive f_fsid from on-disk fsuuid and dev_t Date: Fri, 11 Sep 2026 09:07:29 -0700 Message-ID: Organization: Intel Corporation In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPartum1A8a6JTPS2ES6fvQVGjw"; micalg="sha256"; protocol="application/pkcs7-signature" --nextPartum1A8a6JTPS2ES6fvQVGjw Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" On Friday, 11 September 2026 07:51:16 Pacific Daylight Time Anand Suveer Jain wrote: > I wish I had more clarity on how OpenConnect uses the FSID before I > comment. Do you know? Can you shed some light on this? It's openconnect's option --key-password-from-fsid. It uses the FSID encoded in hex format as the key's passphrase. To reproduce, take any key without a password and do: openssl rsa -in unencrypted-key.pem -out encrypted-key.pem And paste your FSID as the password. This is not real security, we all agree. David W can probably remember better why this option exists, but I would suspect it was an IT mandate that a) the key not be left unencrypted on disk and b) be specific to a given machine, avoiding reuse by being copied to another. Ideally, we'd use TPM these days, but there are still a lot of systems without it where Linux runs, and especially a lot of legacy set ups. But very simply, it's the fact that the FSID has been used as a stable identifier and no longer is if the device in question is not itself stable. > Also, a couple of quick checks: > > Is the underlying device MAJ:MIN changing before and after the upgrade? Unknown. It's LVM and I don't know if the order of activation of LVs is guaranteed. I wouldn't rely on it. I'll tell you next time I reboot if the order is the same as this: brw-rw---- 1 root disk 254, 0 Sep 7 20:28 cr-auto-1 brw-rw---- 1 root disk 254, 1 Sep 7 20:28 system-root brw-rw---- 1 root disk 254, 2 Sep 7 20:28 system-swap brw-rw---- 1 root disk 254, 3 Sep 7 20:28 system-pool_tmeta brw-rw---- 1 root disk 254, 4 Sep 7 20:28 system-pool_tdata brw-rw---- 1 root disk 254, 5 Sep 7 20:28 system-pool-tpool brw-rw---- 1 root disk 254, 6 Sep 7 20:28 system-pool brw-rw---- 1 root disk 254, 7 Sep 7 20:28 system-stuff brw-rw---- 1 root disk 254, 8 Sep 7 20:28 system-home brw-rw---- 1 root disk 254, 9 Sep 7 20:28 system-stuff2 Either way, the point is that it changed from 7.1 when the MAJ:MIN was not mixed in. > Are the original and cloned Btrfs filesystems mounted simultaneously? No cloning is involved. > Patch v3 (1/2) keeps the FSID persistent from the on-disk superblock and > stops exposing the internal random FSID. However, if OpenConnect relies > on statfs.f_fsid, patch v3 (2/2) now derives f_fsid from the underlying > MAJ:MIN. -- Thiago Macieira - thiago.macieira (AT) intel.com Principal Engineer - Intel DCG - Platform & Sys. 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