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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Thu, 14 Sep 2023 11:43:50 +0200
Message-ID: <CAJfpeguJ+H7HkZOgZrJ7VmTY_GhQ5uqueZH+DL9EuEeX5kgXQw@mail.gmail.com>
Subject: Re: [RFC PATCH 1/3] add unique mount ID
To:     Christian Brauner <brauner@kernel.org>
Cc:     Miklos Szeredi <mszeredi@redhat.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-api@vger.kernel.org, linux-man@vger.kernel.org,
        linux-security-module@vger.kernel.org, Karel Zak <kzak@redhat.com>,
        Ian Kent <raven@themaw.net>,
        David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <christian@brauner.io>,
        Amir Goldstein <amir73il@gmail.com>
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On Thu, 14 Sept 2023 at 11:36, Christian Brauner <brauner@kernel.org> wrote:
>
> > Yes, one concern is that humans confuse the old and the new ID.
> >
> > I also think it makes sense to allow the new interfaces to look up the
> > mount based on either the old or the new ID.   But I could be wrong
>
> Hm, mount id recycling may happen so quickly that for service restarts
> with a lot of mounts this becomes mostly useless...

Agreed.  The old ID is mostly useful for human interaction.

>
> > there, since that might encourage bad code.  Maybe the new interface
> > should only use take the new ID, which means no mixed use of
> > /proc/$$/mountinfo and statmnt/listmnt.
>
> ... so I think that is indeed the better way of doing things. There's no
> need to encourage userspace to mix both identifiers.

Okay.

But I'd still leave the 2^32 offset for human confusion avoidance.

Thanks,
Miklos