Re: LInux NFSv4.1 client and server- case insensitive filesystems supported?

Chuck Lever
2025-06-08T21:52:45Z

On 6/8/25 4:52 PM, Theodore Ts'o wrote:
> On Sun, Jun 08, 2025 at 12:29:30PM -0400, Chuck Lever wrote:
>>
>> For some reason I thought case-insensitivity support was merged more
>> recently than that. I recall it first appearing as a session at LSF in
>> Park City, but maybe that one was in 2018.
>
> commit b886ee3e778ec2ad43e276fd378ab492cf6819b7
> Author: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
> Date: Thu Apr 25 14:12:08 2019 -0400
>
> ext4: Support case-insensitive file name lookups
>
>> nfs(5) describes the lookupcache= mount option. It controls how the
>> Linux NFS client caches positive and negative lookup results.
>
> Has anyone just tried it? It might just work. To create a
> case-folded directory:
>
> # mke2fs -Fq -t ext4 -O casefold /dev/vdc
> # mount /dev/vdc /vdc
> # mkdir /vdc/casefold
> # chattr +F /vdc/casefold
> # cp /etc/issue /vdc/casefold/MaDNeSS
> # cat /vdc/casefold/madness
>
> Then export the directory and mount it via NFS, and let us know how it
> goes. I'm currently on a cruise ship so it's a bit harder for me to
> do the experiment myself. :-)

NFSD currently asserts that all exported file systems are case-sensitive
and case-preserving (either via NFSv3 or NFSv4). There is very likely
some additional work necessary.

Ted, do you happen to know if there are any fstests that exercise case-
insensitive lookups? I would not regard that simple test as "job done!
put pencil down!" :-)

--
Chuck Lever