Re: Testing if two open descriptors refer to the same inode

[Florian Weimer]

* Mateusz Guzik:

> On Mon, Jul 29, 2024 at 08:55:46AM +0200, Florian Weimer wrote:
>> It was pointed out to me that inode numbers on Linux are no longer
>> expected to be unique per file system, even for local file systems.
>
> I don't know if I'm parsing this correctly.
>
> Are you claiming on-disk inode numbers are not guaranteed unique per
> filesystem? It sounds like utter breakage, with capital 'f'.

Yes, POSIX semantics and traditional Linux semantics for POSIX-like
local file systems are different.

> While the above is not what's needed here, I guess it sets a precedent
> for F_DUPINODE_QUERY (or whatever other name) to be added to handily
> compare inode pointers. It may be worthwhile regardless of the above.
> (or maybe kcmp could be extended?)

I looked at kcmp as well, but I think it's dependent on
checkpoint/restore.  File sameness checks are much more basic than that.

Thanks,
Florian