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Date: Wed, 14 Jan 2026 07:26:08 +0100
From: Christoph Hellwig <hch@lst.de>
To: =?iso-8859-1?Q?Andr=E9?= Almeida <andrealmeid@igalia.com>
Cc: Christoph Hellwig <hch@lst.de>, Chuck Lever <chuck.lever@oracle.com>,
	Jeff Layton <jlayton@kernel.org>, NeilBrown <neil@brown.name>,
	Olga Kornievskaia <okorniev@redhat.com>,
	Dai Ngo <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
	Carlos Maiolino <cem@kernel.org>,
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	David Sterba <dsterba@suse.com>, Miklos Szeredi <miklos@szeredi.hu>,
	Christian Brauner <brauner@kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.cz>,
	linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-btrfs@vger.kernel.org, linux-unionfs@vger.kernel.org,
	kernel-dev@igalia.com
Subject: Re: [PATCH 3/3] ovl: Use real disk UUID for origin file handles
Message-ID: <20260114062608.GB10805@lst.de>
References: <20260114-tonyk-get_disk_uuid-v1-0-e6a319e25d57@igalia.com> <20260114-tonyk-get_disk_uuid-v1-3-e6a319e25d57@igalia.com>
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User-Agent: Mutt/1.5.17 (2007-11-01)

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.