Bug#1114898: NFSv4.2 reports "Operation Not Supported" on getxattr calls

[Brad Barnett <debian-bugs5@L8R.net>]

Package: linux-image-amd64
Version: 6.12.43-1

NFSv4.2 reports "Operation Not Supported" on getxattr calls.

The following is with the same NFS backend, and same mount options.  The
NFS server reports name: "Linux NFSv4.2 [an identifier]" under 
/proc/fs/nfsd/clients/*/info for both clients.

Bookworm:

# touch testfile
# setfattr -h -n user.test -v yes testfile
# getfattr -h -n user.test testfile
# file: testfile
user.test="yes"

Trixie:

# setfattr -h -n user.test -v yes testfile
setfattr: testfile: Operation not supported

# getfattr -h -n user.test testfile
testfile: user.test: Operation not supported

There seems to be a regression in set/getxattr handling in 6.12 and other
branches.  This may be helpful:

https://marc.info/?l=linux-nfs&m=175643910429853&w=2