linux-kernel - Re: [RFC PATCH 1/3] add unique mount ID

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Date:   Fri, 15 Sep 2023 09:31:28 +0800
From:   Ian Kent <raven@...maw.net>
To:     Miklos Szeredi <miklos@...redi.hu>,
        Christian Brauner <brauner@...nel.org>
Cc:     Miklos Szeredi <mszeredi@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-man@...r.kernel.org,
        linux-security-module@...r.kernel.org, Karel Zak <kzak@...hat.com>,
        David Howells <dhowells@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian@...uner.io>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [RFC PATCH 1/3] add unique mount ID

On 14/9/23 17:43, Miklos Szeredi wrote:
> On Thu, 14 Sept 2023 at 11:36, Christian Brauner <brauner@...nel.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.

I think having both is leaving more opportunity for confusion and the new

mount id has a different name so I think start the move to using that now

and only allow the new one for lookups.


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

Yep, agreed.


Ian