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

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Message-ID: <20260115063630.GA9671@lst.de>
Date: Thu, 15 Jan 2026 07:36:30 +0100
From: Christoph Hellwig <hch@....de>
To: Amir Goldstein <amir73il@...il.com>
Cc: André Almeida <andrealmeid@...lia.com>,
	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>, 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 06:54:37PM +0100, Amir Goldstein wrote:
> Perhaps this is the wrong way to abstract what overlayfs needs from real fs.
> Maybe better to extend ->encode_fh() to take a flags argument (see similar
> suggested patch at [1]) and let overlayfs do something like:

Encoding the uuid into the file handle in the kernel is the right thing
for NFS as well.  Hacking in the uuids in userspace instead of the kernel
was done initially because there was no good kernel uuid infrastructure.
So doing this in general and have NFS use it when available would be
beneficial for everyone.