linux-kernel - Re: [PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications [ver #5]

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Message-ID: <CAJfpeguvLMCw1H8+DPsfZE_k0sEiRtA17pD9HjnceSsAvqqAZw@mail.gmail.com>
Date:   Mon, 3 Aug 2020 11:29:27 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     David Howells <dhowells@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Ian Kent <raven@...maw.net>,
        Christian Brauner <christian@...uner.io>, andres@...razel.de,
        Jeff Layton <jlayton@...hat.com>, dray@...hat.com,
        Karel Zak <kzak@...hat.com>, keyrings@...r.kernel.org,
        Linux API <linux-api@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        LSM <linux-security-module@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/17] watch_queue: Implement mount topology and attribute
 change notifications [ver #5]

On Thu, Jul 23, 2020 at 12:48 PM David Howells <dhowells@...hat.com> wrote:

>
> > >                 __u32   topology_changes;
> > >                 __u32   attr_changes;
> > >                 __u32   aux_topology_changes;
> >
> > Being 32bit this introduces wraparound effects.  Is that really worth it?
>
> You'd have to make 2 billion changes without whoever's monitoring getting a
> chance to update their counters.  But maybe it's not worth it putting them
> here.  If you'd prefer, I can make the counters all 64-bit and just retrieve
> them with fsinfo().

Yes, I think that would be preferable.

> > >         n->watch.info & NOTIFY_MOUNT_IS_RECURSIVE if true indicates that
> > >         the notifcation was generated by an event (eg. SETATTR) that was
> > >         applied recursively.  The notification is only generated for the
> > >         object that initially triggered it.
> >
> > Unused in this patchset.  Please don't add things to the API which are not
> > used.
>
> Christian Brauner has patches for mount_setattr() that will need to use this.

Fine, then that patch can add the flag.

Thanks,
Miklos