[rfc] 64-bit inode numbers

Kostik Belousov kostikbel at gmail.com
Thu Jun 23 22:26:35 UTC 2011

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.

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