RHEL6.8: NFS4.1 client connected to NetApp with write delegations enabled enters loop of WRITE / NFS4ERR_BAD_STATEID or SETATTR / NFS4ERR_ADMIN_REVOKED when the same file is written from a 4.0 client

Issue

I made a very simple testcase that can be run on two nodes where each node repeatedly writes the nodename and date to a given file without any locking.

# for i in $(seq 1 1000); do echo "$(hostname) $(date)" >> /mnt/nfs4/file; done

Since NFS4 delegations are enabled, this test will cause one client to obtain a delegation, write to the file for a while, then the delegation will be called back by the NFS server as a result of the second client's conflicting open.

I've found if I run this with on one NFS 4.0 client (for example, RHEL6.7) and then on a second client using NFS 4.1 either:
- run the same loop to the same file
- try to truncate the file

I can get the second 4.1 into an infinite loop of either WRITE / BAD_STATEID or SETATTR / ADMIN_REVOKED. I have to reboot the client to recover.