[Unionfs] unmounting order during shutdown [was: Re: unionfs 2.2.3 OOPS]

[Erez Zadok]

In message <47E9FEE5.2010809 at mozilla.com>, Dave Miller writes:
> So after applying this patch to 2.3 and deploying it (might as well have 
> called it 2.3.1 ;) I got the following about a half hour after booting 
> into it:
> 
> Mar 26 00:20:03 dm-stage02 kernel: unionfs: new lower inode mtime 
> (bindex=0, name=2008-03-25-15-trunk)
> Mar 26 00:20:04 dm-stage02 kernel: unionfs: unionfs: new generation 
> number 57
> Mar 26 00:20:04 dm-stage02 kernel: alidatalidation
> Mar 26 00:20:05 dm-stage02 kernel: alidation
> Mar 26 00:20:05 dm-stage02 kernel: 
> alidaalidaaaliaalialidaalialialidalidaalidatioalidatialidalidation
> Mar 26 00:20:05 dm-stage02 kernel: <alidalalidalidationalidation
> Mar 26 00:20:05 dm-stage02 kernel: <7alidalidationalidation
> Mar 26 00:20:05 dm-stage02 kernel: alalidationalialidation
> Mar 26 00:20:05 dm-stage02 kernel: <alidatioalidation
> Mar 26 00:20:05 dm-stage02 kernel: alidation
> Mar 26 00:20:05 dm-stage02 kernel: <7alidation
> Mar 26 00:20:05 dm-stage02 kernel: alalidation
> Mar 26 00:20:06 dm-stage02 kernel: <7alidation
> Mar 26 00:20:06 dm-stage02 kernel: <alidalialidalidaalidation
> Mar 26 00:20:06 dm-stage02 kernel: alidation
> Mar 26 00:20:06 dm-stage02 kernel: alidatioalialidatalidation
> Mar 26 00:20:06 dm-stage02 kernel: alidation
> Mar 26 00:20:06 dm-stage02 kernel: alidation
> 
> And those last 16 lines or some variation of them repeated for about 
> another 20K lines while file operations that touched the unionfs mount 
> would hang, until I power cycled the machine.  vewy stwange....

Very strange indeed.  I know where the above "console storm" comes from,
just not sure why.  Investigating...

In the mean time, two things.

First, your k/syslog output always seems to overlap somehow.  Is this ouput
from dmesg directly, or from /var/log/* ? are you writing to your log files
synchrnously, or async (the "-" in front of log file names in
/etc/syslog.conf).  Can you try to add

	kern.*	-/var/log/kern

   or even

	*.*	-/var/log/all

so we can better see all the messages?

> The kernel it upgraded from was 2.2.4, which is what I rebooted back 
> into after that.  Dunno if I should try again... :)

Second, can you apply the small patch below on top of 2.2.4 and see if it
helps?  I have a feeling that was definitely affecting you.

> > diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c
> > index e5cb235..4cddc83 100644
> > --- a/fs/unionfs/super.c
> > +++ b/fs/unionfs/super.c
> > @@ -755,7 +755,7 @@ out_no_change:
> >  	/* grab new lower super references; release old ones */
> >  	for (i = 0; i < new_branches; i++)
> >  		atomic_inc(&new_data[i].sb->s_active);
> > -	for (i = 0; i < new_branches; i++)
> > +	for (i = 0; i < sbmax(sb); i++)
> >  		atomic_dec(&UNIONFS_SB(sb)->data[i].sb->s_active);
> >  
> >  	/* copy new vectors into their correct place */

Thanks,
Erez.