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Subject: Re: [PATCH 13/17] watch_queue: Implement mount topology and
 attribute change notifications [ver #5]
From:   Ian Kent <raven@themaw.net>
To:     David Howells <dhowells@redhat.com>
Cc:     Miklos Szeredi <miklos@szeredi.hu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Nicolas Dichtel <nicolas.dichtel@6wind.com>,
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        Jeff Layton <jlayton@redhat.com>, dray@redhat.com,
        Karel Zak <kzak@redhat.com>, keyrings@vger.kernel.org,
        Linux API <linux-api@vger.kernel.org>,
        linux-fsdevel@vger.kernel.org,
        LSM <linux-security-module@vger.kernel.org>,
        linux-kernel@vger.kernel.org
Date:   Mon, 03 Aug 2020 22:30:26 +0800
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On Mon, 2020-08-03 at 13:31 +0100, David Howells wrote:
> Ian Kent <raven@themaw.net> wrote:
> 
> > > I'm changing it so that the fields are 64-bit, but initialised
> > > with the
> > > existing mount ID in the notifications set.  The fsinfo set
> > > changes that
> > > to a unique ID.  I'm tempted to make the unique IDs start at
> > > UINT_MAX+1 to
> > > disambiguate them.
> > 
> > Mmm ... so what would I use as a mount id that's not used, like
> > NULL
> > for strings?
> 
> Zero is skipped, so you could use that.
> 
> > I'm using -1 now but changing this will mean I need something
> > different.
> 
> It's 64-bits, so you're not likely to see it reach -1, even if it
> does start
> at UINT_MAX+1.

Ha, either or, I don't think it will be a problem, there's
bound to be a few changes so the components using this will
need to change a bit before it's finalized, shouldn't be a
big deal I think. At least not for me and shouldn't be much
for libmount either I think.

Ian