Is NFSv4 mount interruptible?

[Slawa Olhovchenkov]

On Tue, Aug 02, 2016 at 10:48:52PM +0000, Rick Macklem wrote:

> Slawa wrote:
> >I have autofs NFSv4 mount with /etc/nfs.map:
> >
> >/NFS    -nfsv4,intr,soft,sec=krb5i,gssname=host storage01:/
> >
> >Currently I am see NFS hung and I am can't kill shell and can't
> >unmount /NFS.
> >
> >Is NFSv4 mount interruptible?
> >Or intr support only by NFSv3?
> Well, in the BUGS section of "man mount_nfs" it notes that soft and intr cannot be
> safely used with NFSv4. The problem is that, if an RPC that updates state (Open, Close,...)
> terminates, then the state is no longer usable.
> 
> You can "umount -f" the file system, but only if no other "umount" is already in progress.
> (I am working on a new umount option that will allow "umount -f" to succeed when another
>  umount is stuck. It requires "umount(8)" to avoid all the path checking, etc.)
> 
> Personally, I would never use "soft" for any mount (except read-only maybe), since it can
> result in a write failure when the NFS server is slow. Using "intr" should be ok for NFSv3,
> since it is stateless.

For me, this mount like r/o.
I am don't have significant write to this mount.
If some data lost I am able to create this data again.
Currently NFS hang after long idle.

I am try to do umount, w/o success:

# ps -ax | grep mou
  706  -  Is        0:00.00 /usr/sbin/moused -p /dev/ums0 -t auto -I /var/run/moused.ums0.pid
 1116  -  Ds        1:16.50 /usr/sbin/autounmountd
86794  3- T+        0:00.00 umount -f /NFS

# procstat 86794
  PID  PPID  PGID   SID  TSID THR LOGIN    WCHAN     EMUL          COMM        
86794 86791 86794 86788 86788   1 admin    autofsvl  FreeBSD ELF64 umount      

# procstat 1116
  PID  PPID  PGID   SID  TSID THR LOGIN    WCHAN     EMUL          COMM
 1116     1  1116  1116     0   1 root     newnfs    FreeBSD ELF64 autounmountd