6.12 rc6 - Exclusive Shares Not Compatible with NFSv4.

This was emailed in as well. #25089

From the remote host-

root@kube01:~# mount -t nfs4 -o nfsvers=4.0,actimeo=1,soft,timeo=300,retry=2 10.100.5.2:/mnt/user/longhorn-backups test/ mount.nfs4: mounting 10.100.5.2:/mnt/user/longhorn-backups failed, reason given by server: No such file or directory

From Unraid
root@Tower:/mnt/user# cat /etc/exports

...

"/mnt/user/longhorn-backups" -fsid=105,async,no_subtree_check 10.100.5.0/24(sec=sys,rw,insecure,anongid=100,anonuid=99,all_squash)

...

root@Tower:/mnt/user# ls -al /mnt/user 

longhorn-backups -> /mnt/main/longhorn-backups/ 

NFS Shares:

root@Tower:/mnt/main/home/root# ./showNfsClients
v3 clients: (via /var/lib/nfs/rmtab)
10.100.5.100:/mnt/main/photos:0x00000001
10.100.5.105:/mnt/main/nextcloud:0x00000001
10.100.5.105:/mnt/cache/scanned:0x00000001
10.100.5.105:/mnt/main/documents:0x00000001

v4 clients: (via /proc/fs/nfsd/clients)
address: "10.100.5.100:798"
name: "Linux NFSv4.2 longhorn-manager-j2wk7"
address: "10.100.5.106:847"
name: "Linux NFSv4.0 longhorn-manager-hgtt8/10.100.5.2"
address: "10.100.5.105:681"
name: "Linux NFSv4.2 instance-manager-r-23866f720a1af5bf2236875845f4f132"
address: "10.100.5.105:701"
name: "Linux NFSv4.2 longhorn-manager-7txwq"
address: "10.100.5.106:909"
name: "Linux NFSv4.2 instance-manager-r-9613737d8c4e4685af4dda69f50a4f50"
address: "10.100.5.100:659"
name: "Linux NFSv4.2 instance-manager-r-ce2be797b831f1d30f228947e0bec7a3"

To note, this ONLY impacts the following conditions:

1. Remote client is using NFSv4, instead of NFSv3.

2. Share, is "Exclusive share" added in rc6.

3. ZFS may, or may not be a factor here. 

I do believe this issue is due to nfsv4 not liking the symlink. 

Adding a secondary storage, converting back to a FUSE/SHFS mount, addresses issue.