kern/118360: NFS-Server gives "Permission denied" after taking a snapshot

[Michael Moll]

>Number:         118360
>Category:       kern
>Synopsis:       NFS-Server gives "Permission denied" after taking a snapshot
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Nov 30 19:10:03 UTC 2007
>Closed-Date:
>Last-Modified:
>Originator:     Michael Moll
>Release:        RELENG_7
>Organization:
kvedulv.de
>Environment:
FreeBSD marduk.kvedulv.de 7.0-BETA3 FreeBSD 7.0-BETA3 #0: Fri Nov 30 14:57:51 CET 2007     mmoll at marduk.kvedulv.de:/usr/obj/usr/src/sys/MARDUK  i386
>Description:
[Export some directories via NFS from marduk to emperor]

root at marduk:~# cat /etc/exports          
/usr/local/music
/usr/ports/distfiles

root at emperor:~# mount 192.168.200.11:/usr/ports/distfiles /mnt
root at emperor:~# df -h /mnt
Filesystem                             Size    Used   Avail Capacity  Mounted on
192.168.200.11:/usr/ports/distfiles    7.7G    3.8G    3.4G    53%    /mnt

[everything ok... now take a snapshot]

root at marduk:~# mount -u -o snapshot /usr/.snap/snapshot.301120071938 /usr

root at marduk:~# ls -al /usr/.snap/
total 408484
drwxrwxr-x   2 root  operator         512 Nov 30 19:39 .
drwxr-xr-x  18 root  wheel            512 Nov 30 15:42 ..
-r--------   1 root  operator  8589935000 Nov 30 19:33 snapshot.191120071245
-r--------   1 root  operator  8589935000 Nov 30 19:40 snapshot.301120071938

[still everything ok, data is accessible]

root at emperor:~# head -n 4 /mnt/jpegexiforient.c
/*
 * jpegexiforient.c
 *
 * This is a utility program to get and set the Exif Orientation Tag.

[now try to mount it again...]

root at emperor:~# umount /mnt
root at emperor:~# mount 192.168.200.11:/usr/ports/distfiles /mnt
[udp] 192.168.200.11:/usr/ports/distfiles: Permission denied

root at marduk:~# tail -n 1 /var/log/messages
Nov 30 19:42:25 marduk mountd[582]: mount request denied from 192.168.200.1 for /usr/ports/distfiles
>How-To-Repeat:
I can reproduce this with a FreeBSD-7 and a Linux-NFS-client, so the problem is on the server-side
>Fix:
Rebooting the NFS-server-machine is the only way I found to make the directory NFS-accessable again.

>Release-Note:
>Audit-Trail:
>Unformatted: