kern/41331: NFS write error while mounting vnd on NFS server

[fun%naobsd.org@localhost]

>Number:         41331
>Category:       kern
>Synopsis:       NFS write error while mounting vnd on NFS server
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat May 02 04:20:01 +0000 2009
>Originator:     FUKAUMI Naoki
>Release:        NetBSD 5.0
>Organization:
        FUKAUMI Naoki
>Environment:
System: NetBSD t105.naobsd.org 5.0 NetBSD 5.0 (T105_XEN) #0: Wed Apr 29 
21:34:46 JST 2009 
root%t105.naobsd.org@localhost:/usr/obj/amd64/sys/arch/amd64/compile/T105_XEN 
amd64
Architecture: x86_64
Machine: amd64
>Description:
        I'm setting up Xen environment. dom0 is NFS server and domU is
        NFS client.

        when compiling pkgsrc on NFS area on domU, I made new vnd image
        and mount vnd partition on dom0. then, compiling pkgsrc is
        stopped suddenly with "permission denied" message.

        I can reproduce this problem more general way. (see below)
>How-To-Repeat:
        [on NFS client]
        # mount nfs_server:/foo /bar
        # cd /bar
        # pax -rzf tarball.tgz (contiguous write operation)
        [on NFS server]
        # vnconfig vndX img
        # newfs vndXa
        # mount /dev/vndXa /mnt (during write operation on NFS client)

        you'll get write error on NFS client like:

        pax: Unable to obtain block size for file 
pkgsrc/archivers/lha/patches/CVS/Root (Input/output error)
        pax: Cannot close file descriptor on 
pkgsrc/archivers/lha/patches/CVS/Root.14473n (Permission denied)
        pax: Cannot set permissions on 
pkgsrc/archivers/lha/patches/CVS/Root.14473n (Input/output error)
        pax: Access/modification time set failed on: 
pkgsrc/archivers/lha/patches/CVS/Root.14473n (Input/output error)
>Fix:
        yes, please.