Re: [PATCH] fs: inode: Reduce volatile inode wraparound risk when ino_t is 64 bit

[Chris Down]

J. Bruce Fields writes:
> I thought that (dev, inum) was supposed to be unique from creation to
> last unlink (and last close), and (dev, inum, generation) was supposed
> to be unique for all time.

Sure, but I mean, we don't really protect against even the first case.

> > I didn't mention generation because, even though it's set on tmpfs
> > (to prandom_u32()), it's not possible to evaluate it from userspace
> > since `ioctl` returns ENOTTY. We can't ask userspace applications to
> > introspect on an inode attribute that they can't even access :-)
>
> Is there any reason not to add IOC_GETVERSION support to tmpfs?
>
> I wonder if statx should return it too?

We can, but that seems like a tangential discussion/patch series. For the 
second case especially, that's something we should do separately from this 
patchset, since this demonstrably fixes issues encountered in production, and 
extending a user-facing APIs is likely to be a much more extensive discussion.

(Also, this one in particular has advanced quite a lot since this v1 patch :-))