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Description of problem:
I want to test export option 'hide', so ,I create /etc/exports:

====
/tmp *(rw,no_root_squash,hide)
/tmp/test *(rw,no_root_squash)
/etc *(rw,no_root_squash)
====

Then, mount shared directories,
#mount -o vers=4 localhost:/etc /tmp/test
#mount -o vers=4 localhost:/tmp /mnt/test

Then , check that 'hide' work fine, and umount
#umount /mnt/test
#umount /mnt/test  <=== error

[root@ibm-ls22-01 ~]# umount /tmp/test
umount.nfs: /tmp/test: device is busy
umount.nfs: /tmp/test: device is busy
[root@ibm-ls22-01 ~]# service nfs stop
Shutting down NFS mountd: [  OK  ]
Shutting down NFS daemon: [  OK  ]
Shutting down NFS quotas: [  OK  ]
^C

And I open rpcdebug, find that RPC prints cyclic debug message.(attacked)


Version-Release number of selected component (if applicable):
2.6.32-188.el6.x86_64
nfs-utils-1.2.3-7.el6.x86_64

Created attachment 518810 [details]
cyclic RPC debug message

ops :    cyclic debug message.(attached)

I have use 'hide' wrongly, this bug should have nothing with 'hide', it may be caused by config file in /etc.

If I delete '/tmp/test *(rw,no_root_squash)', I could umount /tmp/test successfully. Maybe this is not a bug!

Right, you're not expected to be able to unmount exported filesystems.

Also, it looks like you're trying to re-export nfs (by mounting an nfs filesystem at /tmp/test, and also exporting /tmp/test).  That's not expected to work either.