Re: umount error: device is busy after nfs + lock

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Mon, 2006-05-15 at 11:59 -0700, wang dengyi wrote:
> Hello,
> 
> When I ran ltp test case:tlocklfs, I met a old problem
> with the kernel:2.6.9. I can not umount a file system
> after nfs and lock using it. Here is the steps.

Kernel 2.6.9 is almost 2 years old, and the NFS locking has changed a
_lot_ since then. Can you reproduce this with a recent kernel?

Cheers,
  Trond

>  1) mount /dev/sda3 /xyz
>  2) export /xyz
>  3) restart nfs
>  4) mount 127.0.0.1:/xyz /mnt/nfs_xyz
>  5) run the special lock test program: "tlocklfs -t 7
> /mnt/nfs_xyz
>  6) umount /mnt/nfs_xyz
>  7) stop nfs
>  8) umount /xyz
> Then I got the error: "umount /xyz: device is busy".
> And the error displays twice. 
> 
> If I run the different lock test case for the step 5,
> the umount works fine. It only failed on the test case
> 7 from tlocklfs. 
> 
> There are 2 processes in this special test case.
> First, the parent process "setlk" for a file from nfs
> file system. Then the child process "setlkw". At the
> end, the parent and the child process unlock the file.
> 
> 
> With some debug line in the code, I found the file
> system's "mnt_count" is 3 instead of 2 before
> umounting it. I traced back the problem and I'm lost
> in linux/net/sunrpc/sched.c. Could anyone give me some
> hint? Thank you very much.
> 
> Best regard
> 
> Dengyi Wang
>   
> 
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