Thank you for the reproducer! I was able to reproduce the file
corruption with a modified version of the C file in which the
destination file times were set. Otherwise there is no corruption. I'm
attaching the modified file. I'm going to file a bug with Red Hat using
Paul's modified reproducer, if that's okay.

The nfs mounted filesystem is on another Red Hat system. I'm going to
file the Red Hat bug before gathering additional information.

Thanks for your help!

David