Re: Bug#563254: du: bind mount causes corrupted filesystem warning (despite -x !)

[Alan Jenkins]

Jim Meyering wrote:
> Alan Jenkins wrote:
>   
> > Package: coreutils
> > Version: 8.1-1
> > Severity: normal
> >
> >
> > To reproduce:
> >
> > $ mkdir -p /mnt/root
> > $ mount --bind / /mnt/root
> >
> > (I have this in /etc/fstab...
> >  it lets me access parts of / which are hidden by other mounted filesystems -
> >  this happens to be useful for reasons too long and obscure to be worth 
> > explaining)
> >
> > $ du -x
> > du: WARNING: Circular directory structure.
> > This almost certainly means that you have a corrupted file system.
> > NOTIFY YOUR SYSTEM MANAGER.
> > The following directory is part of the cycle:
> >   `./mnt/root'
> > ....
> >     
>
> Thanks for the report.
> I confirm that this still happens with the latest.
>
> For now, I suggest you use e.g.,
>
>     du --exclude=/mnt -x /
>
> Unless such bind mounts appear to be common,
> I may just leave the current semantics as they are.
>
> By the way, would you want du to traverse each
> root partition directory twice?
>   

No.  I was thinking that -x would treat bind mounts like other mounts, 
and not traverse them.

I guess the problem is that -x is taken to mean "stay on this 
_filesystem_ only", as opposed to "stay on this _mount_ only".

And "stay on this filesystem" is probably easier to implement; you just 
check st_dev.  "Stay on this mount" requires checking /etc/mtab or 
/proc/mounts.

It doesn't seem too hard to add an extra check before printing the 
warning.  But I agree this is probably obscure, so I don't blame you for 
not being very bothered about it :-).

Thanks
Alan