Can not read from ZFS exported over NFSv4 but write to it

[Yamagi Burmeister]

Hello,
I have 2 boxes. Both of them are running FreeBSD 9.1-RC2. On box A a
ZFS filesystem and an UFS filesystem are exported over NFSv4. Both
filesystems are mounted on box B. On box B the UFS filesystem is
working as expected. But I'm only able write to the ZFS filesystem,
when trying to read from it only a small amount of data is transmitted
before the NFSv4 mount stalls. A subsequent "umount -f" takes several
minutes to complete. This behavior is 100% reproduceable.

The /etc/exports on box A:

 # ZFS
 /usr/home/yamagi
 # UFS
 /mnt
 V4: / -sec=sys 192.168.0.13

Mounted on box B:

 % mount
   a:/usr/home/yamagi on /mnt (nfs, nfsv4acls)

After the mount stalled (just try to copy some data) the kernel on box B
shows: 
 nfsv4 client/server protocol prob err=10020
 newnfs server a:/usr/home/yamagi: not responding
 newnfs server a:/usr/home/yamagi: is alive again
 newnfs server a:/usr/home/yamagi: not responding
 ...

But the network connection is stable at all times. Not a single "ping"
failes, the ssh connection between the two hosts works just fine.

The kernel on box A doesn't show anything. The nfsd processes are
looking fine. A "procstat -kk" doesn't show anything:
 
 1844 100392 nfsd             nfsd: master     mi_switch+0x186
 sleepq_catch_signals+0x2cc sleepq_timedwait_sig+0x19 _cv_timedwait_sig
 +0x13c svc_run_internal+0x7a1 svc_run+0x8f nfsrvd_nfsd+0x1c7
 nfssvc_nfsd +0x9b sys_nfssvc+0x90 amd64_syscall+0x546 Xfast_syscall
 +0xf7

 1838 101289 nfsd             -                mi_switch+0x186
 sleepq_catch_signals+0x2cc sleepq_wait_sig+0x16 _cv_wait_sig+0x12e
 seltdwait+0x110 kern_select+0x6ef sys_select+0x5d amd64_syscall+0x546
 Xfast_syscall+0xf7

Any help is welcome. More information can be provided if needed. 

Ciao,
Yamagi

-- 
Homepage:  www.yamagi.org
XMPP:      yamagi at yamagi.org
GnuPG/GPG: 0xEFBCCBCB
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