Date: Wed, 7 Nov 2012 14:01:11 -0500
To: Jack Wang <jack.wang.usish@gmail.com>
Cc: =?utf-8?Q?Mart=C3=ADn?= Cigorraga <msx@archlinux.us>, dahai_tian@usish.com,
        linux-nfs@vger.kernel.org
Subject: Re: hang problem when umount a nfs point
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From: "J. Bruce Fields" <bfields@fieldses.org>
Sender: linux-nfs-owner@vger.kernel.org

On Wed, Nov 07, 2012 at 09:05:51AM +0800, Jack Wang wrote:
> 2012/11/7 Martín Cigorraga <msx@archlinux.us>:
> > On Mon, Nov 5, 2012 at 10:27 PM, Jack Wang <jack.wang.usish@gmail.com>
> > wrote:
> >>
> >> Hi all,
> >>
> >> Anyone who can kindly give some suggestion? or we just put question to
> >> the wrong list?
> >>
> >> Thanks.
> >>
> >> Jack
> >>
> >> 2012/11/1 dahai_tian <dahai_tian@usish.com>:
> >> > Hi all:
> >> >         I mount a local directory to a nfs server. When nfs server is
> >> > stopped
> >> > for some accidental cause, I try to umount the mount point, the umount
> >> > command will hang and 'time out' messages are continually printed in the
> >> > terminal. How can I avoid hanging in this case? BTW, This issue does not
> >> > exist when I changed nfs version from 4 to 3.
> >> >         Look forward to your response, thanks!
> 
> >
> > Hi Jack, use the -l (lazy) switch:
> > # umount -l {your mounted nfs share}
> >
> > Also, I wouldn't recommend 'just to kill' the NFS proces(ses) as it (them)
> > may leave shared memory a mess.
> > (And I would like to see how do you make to mount any NFS share again
> > without booting)
> 
> Thanks Martin for kindly help.
> 
> umount -l did work, but why nfsv3 do not have this problem?

I don't know what it is exactly.  But in general I wouldn't expect
umount to work when the server's unavailable.

--b.