weird NFSv3 getaddr storm when fileserver upgraded to 2.6

weird NFSv3 getaddr storm when fileserver upgraded to 2.6

[dap]

 I've upgraded my NFS server from 2.4.25 to 2.6.9 at friday night and
the 2.4.x clients started to flood it with getaddr requests:
http://innocence.nightwish.hu/dap/getaddrstat/rpcga.html

 clients are 2.4.x boxes with increased 'ac' values:

10_1_1_1:~# cat /proc/mounts 
rootfs / rootfs rw 0 0
/dev/root / nfs rw,v3,rsize=4096,wsize=4096,acregmin=120,acregmax=120,acdirmin=120,acdirmax=120,hard,udp,nocto,nolock,addr=10.1.1.251 0 0
proc /proc proc rw 0 0
devpts /dev/pts devpts rw 0 0
10.1.1.251:/mnt/htdocs /http nfs rw,v3,rsize=32768,wsize=32768,acregmin=120,acregmax=120,acdirmin=120,acdirmax=180,hard,udp,nocto,lock,addr=10.1.1.251 0 0

 there's no getattr flood for some time if I reboot the clients (like
saturday night), but it begins again at a point and only the reboot can
calm it down for a while. 2.4.25 worked fine for months.


-- 
dap