From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 A4E9141C71; Wed, 15 Oct 2025 01:22:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760491371; cv=none; b=GUi9Qy38Unry4uS2IX6A6oNla0byvO4acbynjIdFKDWj0BA8HDlIa2APZ7VnK9j0a9+1y3B1d6x+hq6JM9g0gkAVwNfmpcPgtqDBjgRpC4kkBHtCfBRWa7MMj8BTMfoT9vSgabeFzR1ZaNrrC+hS8RFzm7WqP9/X+tR1+0w2Pl4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760491371; c=relaxed/simple; bh=Yc5XGXuuN+qN0hyc0ljp9Q9Ff4KoJTRT8Q/X5IibrHI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BMLa6/BvKnWrLNYwU+nLb0riJf6EU9syqBE1lbrv0+iVL9BpAMRtFfMBw8OSh1oNlrcD8B+pmxvPKnTX2Z0ReY5gHGBZ+09nmiXDlDhbP1phYlkR7ZE+UE/r9QpOIWbrQEpPSpkgHUVWDsXZGnXX8KSvXyf/zFvVvcIfl7ZfZh0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=0TcGRxhC; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="0TcGRxhC" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=THZdcb8DllowJHnhCUQvYqJQSPdZJPLsVnMT6SOtwf4=; b=0TcGRxhCKoq89Ni7iOr5qY1ewO grLd3vPzNtuEDYvS+35V9FbmaHJHb6TWqqNIcofOHjvn2F6Ph3JwHXbzEAWRMh8NlqANhOkwqOKnk Ttazm8vEYz7pkvcpBe7aPkr833cz09ATTZkNHXg655xNpjnaCRZd7b8x1hGHx1Q0S+fOUtphQJmbT UoG9EQeFBgk3mBJN9Lnwab1zy3SjBIvRsjpDPvrW5p1zDVMxnUoqs/e6ztSPBrTYcCBcl8P1xI49z yPzx+evc8byqhj5Sn6kXUZhl4/pG0/Qbj79COwo1tBVuaVTLzjvID8ze9iJhuKkZz+Z7gzg8HdSQl aazYgT0Q==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8qDy-000000009Qi-01Ha; Wed, 15 Oct 2025 01:22:42 +0000 Date: Tue, 14 Oct 2025 18:22:41 -0700 From: Christoph Hellwig To: Anand Jain Cc: Christoph Hellwig , =?iso-8859-1?Q?Andr=E9?= Almeida , linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-dev@igalia.com, Miklos Szeredi , Amir Goldstein , Chris Mason , David Sterba , "Guilherme G . Piccoli" Subject: Re: [RFC PATCH 1/1] ovl: Use fsid as unique identifier for trusted origin Message-ID: References: <20251014015707.129013-1-andrealmeid@igalia.com> <20251014015707.129013-2-andrealmeid@igalia.com> <5137ce36-c3b4-4a0a-83af-e00892feaf43@gmail.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5137ce36-c3b4-4a0a-83af-e00892feaf43@gmail.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Oct 15, 2025 at 07:46:34AM +0800, Anand Jain wrote: > We needed cloned device mount support for an A/B testing > use case, but changing the on-disk UUID defeats the purpose. > > Right now, ext4 and Btrfs can mount identical devices, > but XFS can't. How about extending this to the common > VFS layer and adding a parameter to tell apart a cloned > device from the same device accessed through multiple > paths? I haven't looked into the details yet, but I can > dig it further. If you clone a device you need to change the user visible uuid/fsid, and you need to do that explicitly to a known either saved or user controlled value. Assigning a random ID is highly dangerous as seen here.