This problem is under consideration. Right now NFS client is playing it
safe by not renaming sources or targets that are busy (dentry count >
1).
The reasons for this are to avoid potential problems with deleting a
file on the server while an inode is in use locally. (Rename may involve
an implicit delete.) Once all of the busy inode bugs have been nailed,
we can look at ways to safely do a rename with busy objects.
Regards,
Bill