Re: [PATCH 00/24] vfs: require filesystems to explicitly opt-in to lease support

From: Christoph Hellwig <hch@infradead.org>
To: Christian Brauner <brauner@kernel.org>
Cc: Jeff Layton <jlayton@kernel.org>,
	Amir Goldstein <amir73il@gmail.com>,
	Chuck Lever <chuck.lever@oracle.com>, Jan Kara <jack@suse.cz>,
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Subject: Re: [PATCH 00/24] vfs: require filesystems to explicitly opt-in to lease support
Date: Tue, 13 Jan 2026 06:54:27 -0800	[thread overview]
Message-ID: <aWZcoyQLvbJKUxDU@infradead.org> (raw)
In-Reply-To: <20260113-mondlicht-raven-82fc4eb70e9d@brauner>

On Tue, Jan 13, 2026 at 09:54:15AM +0100, Christian Brauner wrote:
> I don't think we want to expose cgroupfs via NFS that's super weird.
> It's like remote partial resource management and it would be very
> strange if a remote process suddenly would be able to move things around
> in the cgroup tree. So I would prefer to not do this.
> 
> So my preference would be to really sever file handles from the export
> mechanism so that we can allow stuff like pidfs and nsfs and cgroupfs to
> use file handles via name_to_handle_at() and open_by_handle_at() without
> making them exportable.

I don't understand this discussion.  If someone really wants to
expose say cgroupfs to the network they'll find a way, be that using
a userspace nfs server, samba, 9p or a custom fuse thing.  What's the
benefit of explicitly prohibiting a knfsd export?

(not that I think any of this makes much sense to start with)