Bug 458911

Summary:	umount failed after umount the NFS share
Product:	Red Hat Enterprise Linux 4	Reporter:	masanari iida <masanari_iida>
Component:	kernel	Assignee:	Jeff Layton <jlayton>
Status:	CLOSED NOTABUG	QA Contact:	Martin Jenner <mjenner>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	4.7	CC:	steved
Target Milestone:	rc
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2008-08-19 11:25:42 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description masanari iida 2008-08-13 05:25:32 UTC

Description of problem:
NFS exported filesystem can not be unmuont even though
all nfs-clients unmount the share.


Version-Release number of selected component (if applicable):
RHEL4.7 (kernel 2.6.9-78)
nfs-utils-1.0.6-87.EL4

How reproducible:
Always

Steps to Reproduce:
1. Setup NFS server.
 mount /nfs.
 setup /etc/exports dir.
 Start nfs daemon. 

2. Mount the NFS share from NFS client.
 # mount NFS_Server:/nfs  /mnt

This NFS mount succesful.

3. Umount the NFS share from NFS client.
 # umount /mnt

This NFS umount succesful.

4. Umount /nfs on NFS Server.
 # umount /nfs

Actual results:
Umount fail with following message.

# umount /nfs
umount: /nfs: device is busy
umount: /nfs: device is busy

Expected results:
umount successful without error message.

Workaround: 
(1) umount -l /nfs 
(2) /etc/init.d/nfs restart, then umount /nfs

Additional info:
When umount failed,
 lsof shows no process accessing /nfs
 fuser shows no process accessing /nfs

Comment 1 masanari iida 2008-08-13 05:46:56 UTC

Hello,

Another workaround that I just found was, 
remove export entry in kernel before issue umount.

# exportfs -au 
# umount /nfs

So, my question would be,
" Umount a file system while it was exported by NFS
 got faild. Is this a bug or expected? "

Thanks

Comment 2 Jeff Layton 2008-08-19 11:25:42 UTC

This is expected. An actively exported a filesystem has an active reference and cannot be unmounted. I'm going to close this as NOTABUG. Please reopen it if you have further questions.