[linux-lvm] umount returns device is busy

[Frank Benkstein]

On Tue, 23 Dec 2003 01:06:08 +0100
Spam <spam at tnonline.net> wrote:

> 
> 
> > On Mon, Dec 22, 2003 at 04:10:27PM -0600, P. Larry Nelson wrote:
> >> I've been using LVM now since sometime this past summer and
> >> everything has worked great and as advertised, until I tried
> >> to unmount a logical volume.  And this happens on both RedHat
> >> 9 and ES_3.
> >> 
> >> I had occasion the other day to unmount one of the mounted raid 
> >> arrays in order to upgrade some firmware.  When I tried to do an
> >> unmount command, I got "device is busy".  Ok, I'm cd'd there
> >> from one of my windows or something, so I make sure all open
> >> terminal windows are *not* cd'd there.  Redo the umount command
> >> with same result.  Weird, something's got a file open. So, I did
> >> an lsof command and grep for the device (/dev/VG1/LV1).  Nothing.
> >> I try greping for the mount name (/scratch/cdf).  Nothing.
> >> It will not let me unmount the logical volume.
> >> 
> >> The system in question is running RedHat 9 w/kernel 2.4.20-24.9smp
> >> with RedHat's lvm-1.0.3-12.  I just so happened to have built 
> >> another system using RedHat's ES_3 w/kernel 2.4.21-4.0.1.ELsmp and
> >> their lvm-1.0.3-15, so I thought I'd try it there.  Built an
> >identical> logical volume, mounted it, tested it (works fine), tried
> >to umount> the filesystem with identical results: device is busy. 
> >Checked> again using lsof.  Nothing open on the mounted filesystem.
> >> 
> >> I went checking back thru about 4 months of this list and saw
> >> (apparently) that no one else has this problem.  At this point
> >> I'm a bit baffled why the umount command isn't working.  I've
> >> also seen nothing that might address this in the LVM-HOWTO.
> >> Then again, I could have missed it.
> >> 
> >> Ideas?
> 
> > maybe some kernel service is holding a reference
> > to that device, nfs or samba server comes to mind, 
> > just try to disable them one after the other and
> > see if umount will work ...
> 
>   In  my opinion this is a severe mis-feature (aka: bug) in the Linux
>   kernels.  In  some occasions it is impossible to kill an application
>   when  unmounting  a filesystem. This leads to problems with shutting
>   down  the  system  cleanly.  For  example  a  device might have been
>   temporary  offline  when  samba tried to access it. The samba thread
>   locks  indefinitely  and  it  is impossible to kill it and thus also
>   impossible to unmount the filesystem.
> 
>   Not  sure  if LVM guys can do anything about this though. =) Perhaps
>   you  can  push  kernel  developers to make it easier to recover from
>   these kinds of problems?
> 

Have you tried "fuser -v -m" (see fuser(1)). I think "umount -l" already
serves the your case of unmounting a filesystem where kernel thinks it's
busy but it isn't.

Bye
Frank Benkstein.