Permission denied problem

[Avishay Traeger]

I came across the following error while running a random read benchmark
using krb5p.  I had 6 client machines, each running 4 processes.  Each
process was reading from its own 1GB file that was in its own directory.
During the run, one of the reads failed, and perror() printed
"Permission denied".  This was pretty strange, since the benchmark had
been running for some time.

Then:
$ umount /n/test
(this succeeded with no problem)
$ ls /n/test 
ls: /n/test: Permission denied
$ ll /n/
?--------- ? ?        ?       ?            ? /n/test
$ umount /n/test
umount: /n/test: device is busy

Running the 'mount' command does not show the NFSv4 mount.  However, if
I cat /proc/mounts:
v4server:/ /n/test nfs4 rw,vers=4,rsize=131072,wsize=131072,hard,intr,
proto=tcp,timeo=600,retrans=3,sec=krb5p,addr=v4server 0 0

This does not happen every time I run the benchmark, but I have seen it
three times.  Let me know if you need any more information.

Thanks,
Avishay