[rfc] 64-bit inode numbers

[Rick Macklem]

Kostik Belousov wrote:
> On Thu, Jun 23, 2011 at 06:05:56PM -0400, Garance A Drosehn wrote:
> > On 6/23/11 4:11 AM, Kostik Belousov wrote:
> > >On Thu, Jun 23, 2011 at 09:43:33AM +0300, Gleb Kurtsou wrote:
> > >
> > >>On (22/06/2011 19:19), Garance A Drosehn wrote:
> > >>
> > >>>Sorry for replying to an older message, but a reply made in a
> > >>>different
> > >>>thread reminded me about this project...
> > >>>
> > >>>Also, I may have asked this before. In fact, I'm almost sure that
> > >>>I
> > >>>started
> > >>>a reply to this back in Jan/Feb, but my email client claims I
> > >>>never
> > >>>replied
> > >>>to this topic...
> > >>>
> > >>>Are you increasing only the size of ino_t, or could you also look
> > >>>at
> > >>>increasing the size of dev_t? (just curious...)
> > >>>
> > >>Sure. Incorporating as much of similar changes as possible is
> > >>good.
> > >>I've added Kostik and Matthew to CC list, it's for them to decide.
> > >>
> > >>dev_t on other OSes:
> > >>	NetBSD - uint64_t
> > >>	DragonFly - uint32_t
> > >>	Darwin - __int32_t
> > >>	OpenSolaris - ulong_t
> > >>	Linux - __u32
> > >>
> > >>Considering this I think 3rd party software is not ready for such
> > >>change.
> > >>
> > >>Major/minor mapping to dev_t will get more complicated.
> > >>
> > >>And the most important question: what would you want it for? [...]
> > >>
> > >Indeed, this is the right question.
> > >
> > Consider the thread "Increasing the size of dev_t and ino_t" from
> > freebsd-arch in 2002:
> >
> > http://docs.freebsd.org/mail/archive/2002/freebsd-arch/20020317.freebsd-arch.html
> >
> > In particular, this message by Robert Watson:
> >
> > http://docs.freebsd.org/cgi/getmsg.cgi?fetch=139853+0+archive/2002/freebsd-arch/20020317.freebsd-arch
> >
> > I just participated in an online conference for OpenAFS, and while
> > it
> > isn't exactly taking the world by storm, I keep thinking it would be
> > useful if FreeBSD could map individual AFS volumes to unique dev_t
> > identifiers. And given the way AFS is implemented (as a global
> > filesystem
> > with many cells all reachable at the same time), and given the way
> > most
> > sites deploy AFS (with thousands or tens-of-thousands of individual
> > AFS
> > volumes *per site*), that adds up to a lot of values for dev_t.
> >
> > The upcoming release of OpenAFS should include a working and pretty
> > stable AFS client for FreeBSD, so having a larger dev_t would have a
> > more immediate application than it did back in 2002.
> Am I right that the issue is the uniqueness of the dev_t for each
> AFS volume, as reported by stat(2) ?
> 
> Shouldn't the AFS client synthesize the dev_t for each new volume
> mounted ? It seems that the current 32bit dev_t would be enough,
> since I do not expect to see hundreds of thousands of mounts
> on an single system.
> 
I think the main concern is making sure that the value is not the
same as what another mount already has. That's why mnt_stat.f_fsid
is synthesized for NFS, I think?

> Please note that we do not guarantee dev_t stability across reboots
> even
> for real devices.