From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 1045B387341 for ; Fri, 11 Sep 2026 14:51:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789138281; cv=none; b=XDCtmv/u7xLafKvA5iNFVEBr27AGZvsDu7G3YRf3AHCdX64kmgoJ3I77ZaL3JuA2F7icGPhnsTVdi+9Z/xf9ZTH9G7PXnuTmhxW73Uq/QozsCQaEcPrEY/4Af7UhIpQovIsko/SmKsp/lOUZGFuNRLTFyXmGCmMgulQNLTdvhoY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789138281; c=relaxed/simple; bh=gLC/AqB/EKAkLfSOfvzmCFo4LS7Q7xj+NU1YOjdsuR0=; h=Message-ID:Date:MIME-Version:Subject:To:References:Cc:From: In-Reply-To:Content-Type; b=XNq79Tm605m1CQ3dPiYGDPP9D1VV5JyaBhzPIa4kcUyv3MgwdANCIbFpFvfUS4n+eYXI5W6Rm3jTEvjnFgEzi0Gsf9ij9JWzVtyn9T0EKjd/2BAocrLzySF2ZiUGjisU1OQXMNONSi0Q/QTd6uE351jLHFIQFqr7qxql9zWDJFU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OZV+t9Sa; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OZV+t9Sa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4DD7B1F000FF; Fri, 11 Sep 2026 14:51:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789138279; bh=7+ScKLQ/WdL2S9MFVqlgNfMIMEsmsijc4mcz/mfN2iQ=; h=Date:Subject:To:References:Cc:From:In-Reply-To; b=OZV+t9Sa+rk1N10EAFjrJDIQ28TU6HCj0HwRdRbVoOi1FMZ1OdmsHIXukFD7QP+tw y4YR0GSHjvDco4f2GnOZLo/WHZb3iQRNh09xGYCeM1W6bNGXRMRcQS8XbuVgTS3l+x JpzS5+JzbhQT5/gZ2k9fFLMkJZXAkxtNIVd/XeWjaT/9BNCSw+1rbcGxzhiosWOGG5 fXpt7/ci3pQce+dz0Wpy65VnxmEiNnRWOR2z9/0OSwXz0fGDA801IynUo2fTLfJ7fY 1vFeJlP3k7/RAqfySi6PCoAiGXSDp3U/ZEE7rYORF2QNrN7cfH57gpnSQpqqHRKV6H yW8IMM4H8nxBQ== Message-ID: Date: Fri, 11 Sep 2026 22:51:16 +0800 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] btrfs: derive f_fsid from on-disk fsuuid and dev_t To: Dave Hansen References: Content-Language: en-US Cc: sashal@kernel.org, linux-btrfs@vger.kernel.org, David Woodhouse , David Sterba , "Macieira, Thiago" From: Anand Suveer Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/9/26 20:32, Dave Hansen wrote: > On 2/26/26 06:27, Anand Jain wrote: >> Currently, f_fsid depends on fs_devices->fsid. For cloned devices, this >> value is dynamic and fluctuates across mount cycles. This inconsistency >> breaks persistence for subsystems like IMA. >> >> Switch to a stable derivation using the persistent on-disk fsuuid + >> root id + devt of the block device for the single device filesystem. >> This is consistent as long as the device remains unchanged/replace >> (excludes btrfs device replace secnario for now). > > This commit evidently hit 7.2 and is causing end users some real pain. > Real software uses the FSID to encrypt/decrypt their VPN key files: > > https://github.com/NetworkManager/NetworkManager-openconnect/ > > When this gets applied, those users suddenly can't connect to their VPN > any more. Having a stable derivation does seem like a good idea, of > course. Is there any way to make this transition without breaking > existing userspace and existing users? > > It looks like this is also getting -stable backports. > > Dave, Thanks for the report. 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? Also, a couple of quick checks: Is the underlying device MAJ:MIN changing before and after the upgrade? Are the original and cloned Btrfs filesystems mounted simultaneously? 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.