misc/150910: wsize=16384 on udp nfs mount unusable

[Robert Schulze]

>Number:         150910
>Category:       misc
>Synopsis:       wsize=16384 on udp nfs mount unusable
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Sep 24 11:40:02 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Robert Schulze
>Release:        8.1-RELEASE-p1
>Organization:
>Environment:
FreeBSD xxxxx 8.1-RELEASE-p1 FreeBSD 8.1-RELEASE-p1 #0: Wed Sep 22 10:38:45 CEST 2010     root at xxxxx:/usr/obj/usr/src/sys/WEB  amd64

>Description:
Mounting an NFS filesystem with a large value for wsize results in unexpected behaviour. Before analysis, I got strange errors from vi like "close: permission denied" or "no space left on device" when editing a large textfile and having /var/tmp nfs mounted, although there was enough space.

The client is 8.1-RELEASE-p1, the server 8.0-RELEASE-p3. Both use nfs version 3.

>How-To-Repeat:
# mount_nfs -o noatime,udp,wsize=16384 10.0.0.xx:/var/tmp /var/tmp
# dd if=/dev/zero of=/var/tmp/foo bs=2M count=100
does not return to prompt

# dmesg
nfs server 10.0.0.xx:/var/tmp: not responding
nfs server 10.0.0.xx:/var/tmp: not responding
nfs server 10.0.0.xx:/var/tmp: not responding
nfs server 10.0.0.xx:/var/tmp: not responding
nfs server 10.0.0.xx:/var/tmp: not responding

# top
dd in state "nfsaio"

# umount -f /var/tmp

# mount_nfs -o noatime,udp,wsize=8192 10.0.0.xx:/var/tmp /var/tmp
# dd if=/dev/zero of=/var/tmp/foo bs=2M count=100
100+0 records in
100+0 records out
209715200 bytes transferred in 3.897668 secs (53805303 bytes/sec)

>Fix:


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