Re: [NFS] VFS: Busy inodes after unmount on 2 way SMP

Re: [NFS] VFS: Busy inodes after unmount on 2 way SMP

[Ion Badulescu]

Sorry, I got the autofs list address wrong the first time around. -Ion

---------- Forwarded message ----------

On Thu, 11 Sep 2003 17:11:40 -0700, Arun Sharma <arun.sharma@intel.com> wrote:

> We've seen a few "VFS: Busy inodes after unmount. Self-destruct in 5 seconds.  Have a nice day.." messages on a dual processor NFS client. Here's the use case:
> 
> - Due to network load issues, the NFS server becomes unreachable for some time
> - The automounter tries to expire the mount
> - The unmount finds a couple of busy inodes. Putting some debug printks shows that typically two inodes are busy i.e. have inode->i_count == 1. But they don't have any waiters on inode->i_wait. Further, the inodes that are busy are
> /mnt/foo     -> autofs mount point
> /mnt/foo/bar -> bar is a symbolic link
> 
> It's not clear if this is a NFS issue or a autofs issue, but it's seen often with autofs. Are there any known race conditions that have been fixed after 2.4.20 ? The two calls I'm worried about are:
> 
> fs/autofs/root.c:305:    d_instantiate(dentry, iget(dir->i_sb,ent->ino));
> fs/autofs/root.c:416:    d_instantiate(dentry, iget(dir->i_sb,ino));

I don't know if it's the same issue, but I've seen it many many times 
while testing amd's autofs functionality. It occurs when a non-empty 
autofs filesystem is unmounted, e.g. if it has some leftover 
subdirectories from previous mounts. Therefore I'd say it's quite 
clearly an autofs issue, at least in my case.

Do you see it when shutting down the automounter, or in other cases as 
well?

Ion

-- 
  It is better to keep your mouth shut and be thought a fool,
            than to open it and remove all doubt.

Re: Re: [NFS] VFS: Busy inodes after unmount on 2 way SMP

[H. Peter Anvin]

Ion Badulescu wrote:
> 
> I don't know if it's the same issue, but I've seen it many many times 
> while testing amd's autofs functionality. It occurs when a non-empty 
> autofs filesystem is unmounted, e.g. if it has some leftover 
> subdirectories from previous mounts. Therefore I'd say it's quite 
> clearly an autofs issue, at least in my case.
> 
> Do you see it when shutting down the automounter, or in other cases as 
> well?
> 

This happens when *any* filesystem allows itself to be unmounted without
proper cleanup.  If it happens in normal operation, it is more likely an
NFS problem.  If it happens on automounter shutdown, it's likely an
autofs problem.

	-hpa

Re: Re: [NFS] VFS: Busy inodes after unmount on 2 way SMP

[H. Peter Anvin]

Arun Sharma wrote:
>>
>> Oh yeah, easily. Kill the automounter while some things are mounted,
>> unmount everything by hand but do not rmdir the mountpoints. When you
>> unmount the autofs filesystem itself, you will get the self destruct
>> message.
> 
> Thanks. This reproduces the problem I'm chasing very well. I think this
> is clearly an unacceptable kernel bug.
> 
Indeed.  This is on autofs 3?

	-hpa

Re: Re: [NFS] VFS: Busy inodes after unmount on 2 way SMP

[Arun Sharma]

H. Peter Anvin wrote:
> 
> Indeed.  This is on autofs 3?

Yes.

	-Arun

Re: Re: [NFS] VFS: Busy inodes after unmount on 2 way SMP

[Ion Badulescu]

On Mon, 15 Sep 2003, H. Peter Anvin wrote:

> Arun Sharma wrote:
> >>
> >> Oh yeah, easily. Kill the automounter while some things are mounted,
> >> unmount everything by hand but do not rmdir the mountpoints. When you
> >> unmount the autofs filesystem itself, you will get the self destruct
> >> message.
> > 
> > Thanks. This reproduces the problem I'm chasing very well. I think this
> > is clearly an unacceptable kernel bug.
> > 
> Indeed.  This is on autofs 3?

Both 3 and 4, at least as far as the "self-destruct" message goes.

Ion

-- 
  It is better to keep your mouth shut and be thought a fool,
            than to open it and remove all doubt.

Re: Re: [NFS] VFS: Busy inodes after unmount on 2 way SMP

[Arun Sharma]

H. Peter Anvin wrote:
> 
> Indeed.  This is on autofs 3?
> 

Correction: the problem was primarily seen on autofs4. However the oops that I reported yesterday was autofs3. So the problem affects both.

	-Arun

Re: Re: [NFS] VFS: Busy inodes after unmount on 2 way SMP

[H. Peter Anvin]

Arun Sharma wrote:
> H. Peter Anvin wrote:
> 
>>
>> Indeed.  This is on autofs 3?
>>
> 
> Correction: the problem was primarily seen on autofs4. However the oops
> that I reported yesterday was autofs3. So the problem affects both.
> 
>     -Arun

Thanks.  That's useful information.

	-hpa