NFSv4.x export options to mark export as case-insensitive, case-preserving? Re: LInux NFSv4.1 client and server- case insensitive filesystems supported?

Cedric Blancher
2025-09-09T16:06:56Z

On Tue, 10 Jun 2025 at 07:34, Christoph Hellwig <hch@infradead.org> wrote:
>
> On Mon, Jun 09, 2025 at 10:16:24AM -0400, Chuck Lever wrote:
> > > Date: Wed May 21 16:50:46 2008 +1000
> > >
> > > dcache: Add case-insensitive support d_ci_add() routine
> >
> > My memory must be quite faulty then. I remember there being significant
> > controversy at the Park City LSF around some patches adding support for
> > case insensitivity. But so be it -- I must not have paid terribly close
> > attention due to lack of oxygen.
>
> Well, that is when the ext4 CI code landed, which added the unicode
> normalization, and with that another whole bunch of issues.

Well, no one likes the Han unification, and the mess the Unicode
consortium made from that,
But the Chinese are working on a replacement standard for Unicode, so
that will be a lot of FUN =:-)

> > > That being said no one ever intended any of these to be exported over
> > > NFS, and I also question the sanity of anyone wanting to use case
> > > insensitive file systems over NFS.
> >
> > My sense is that case insensitivity for NFS exports is for Windows-based
> > clients
>
> I still question the sanity of anyone using a Windows NFS client in
> general, but even more so on a case insensitive file system :)

Well, if you want one and the same homedir on both Linux and Windows,
then you have the option between the SMB/CIFS and the Windows NFSv4.2
driver (I'm not counting the Windows NFSv3 driver due lack of ACL
support).
Both, as of September 2025, work fine for us for production usage.

> > Does it, for example, make sense for NFSD to query the file system
> > on its case sensitivity when it prepares an NFSv3 PATHCONF response?
> > Or perhaps only for NFSv4, since NFSv4 pretends to have some recognition
> > of internationalized file names?
>
> Linus hates pathconf any anything like it with passion. Altough we
> basically got it now with statx by tacking it onto a fast path
> interface instead, which he now obviously also hates. But yes, nfsd
> not beeing able to query lots of attributes, including actual important
> ones is largely due to the lack of proper VFS interfaces.

What does Linus recommend as an alternative to pathconf()?

Also, AGAIN the question:
Due lack of a VFS interface and the urgend use case of needing to
export a case-insensitive filesystem via NFSv4.x, could we please get
two /etc/exports options, one setting the case-insensitive boolean
(true, false, get-default-from-fs) and one for case-preserving (true,
false, get-default-from-fs)?

So far LInux nfsd does the WRONG thing here, and exports even
case-insensitive filesystems as case-sensitive. The Windows NFSv4.1
server does it correctly.

Ced
--
Cedric Blancher <cedric.blancher@gmail.com>
[https://plus.google.com/u/0/+CedricBlancher/]
Institute Pasteur