linux-kernel - Re: [PATCH 3/3] ovl: Use real disk UUID for origin file handles

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Message-ID: <20260114062608.GB10805@lst.de>
Date: Wed, 14 Jan 2026 07:26:08 +0100
From: Christoph Hellwig <hch@....de>
To: André Almeida <andrealmeid@...lia.com>
Cc: Christoph Hellwig <hch@....de>, Chuck Lever <chuck.lever@...cle.com>,
	Jeff Layton <jlayton@...nel.org>, NeilBrown <neil@...wn.name>,
	Olga Kornievskaia <okorniev@...hat.com>,
	Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
	Carlos Maiolino <cem@...nel.org>,
	Amir Goldstein <amir73il@...il.com>, Chris Mason <clm@...com>,
	David Sterba <dsterba@...e.com>, Miklos Szeredi <miklos@...redi.hu>,
	Christian Brauner <brauner@...nel.org>,
	Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-btrfs@...r.kernel.org, linux-unionfs@...r.kernel.org,
	kernel-dev@...lia.com
Subject: Re: [PATCH 3/3] ovl: Use real disk UUID for origin file handles

On Wed, Jan 14, 2026 at 01:31:43AM -0300, André Almeida wrote:
> Some filesystem, like btrfs, supports mounting cloned images, but assign
> random UUIDs for them to avoid conflicts. This breaks overlayfs "index"
> check, given that every time the same image is mounted, it get's
> assigned a new UUID.

... and the fix is to not assign random uuid, but to assign a new uuid
to the cloned image that is persisted.  That might need a new field
to distintguish the stamped into the format uuid from the visible
uuid like the xfs metauuid, but not hacks like this.