zfs hang with umount

[Uroš Gruber]

Hi,

I don't know what causes this, but while stopping one of jails I also
run zfs inherit mountpoint on this jails fs. This jail was in stopping
state at this moment. Process than hanged in D state. Then I was doing
some stuff on the server, and while "zfs unmount -f" of that fs,
server chrased. Now everytime I wan't to unmount that fs process hang.
I've managed to send & receive this fs to other fs and mounted
sucessfuly.

Before I reboot and try to destroy this fs, here is output of procstat
-k PID (zfs umount zroot/myfs)

  PID    TID COMM             TDNAME           KSTACK
 3937 100559 zfs              -                mi_switch
sleepq_timedwait _sleep zfs_zget zfs_get_data zil_commit
zfs_freebsd_write VOP_WRITE_APV vnode_pager_generic_putpages
vnode_pager_putpages vm_pageout_flush vm_object_page_collect_flush
vm_object_page_clean vm_object_terminate vnode_destroy_vobject
zfs_freebsd_reclaim vgonel vflush

Is there anything I can check or is this know bug?

Server is running on 9.1-RELEASE

regards

Uros