Re: `du` check for directory loop avoidance

[Bernhard Voelker]

[please don't top-post here]

On 01/13/2014 01:37 AM, Terry Bowling wrote:
> On 12/19/2013 04:37 AM, Bernhard Voelker wrote:
> > On 12/18/2013 07:41 PM, Pádraig Brady wrote:
> > > I need to look into this some more,
> > > but we should at least reword the warning to something more generic
> > BTW: the diagnostic in du(1) has been improved in 8.20 by commit
> >
> >    http://git.sv.gnu.org/cgit/coreutils.git/commit/?id=cf7e1b5b
> >
> > but chcon, chmod, chown, chgrp, rm, and mv are affected, too:
> >
> >    $ git grep emit_cycle_warning | cat
> >    src/chcon.c:          emit_cycle_warning (file_full_name);
> >    src/chmod.c:          emit_cycle_warning (file_full_name);
> >    src/chown-core.c:          emit_cycle_warning (file_full_name);
> >    src/du.c:                emit_cycle_warning (file);
> >    src/remove.c:      emit_cycle_warning (ent->fts_path);
> >    src/system.h:#define emit_cycle_warning(file_name)    \
> >
> > e.g.
> >
> >    $ mount -t tmpfs tmpfs /mnt
> >
> >    $ mkdir /mnt/mnt
> >
> >    $ mount --bind /mnt /mnt/mnt
> >
> >    $ du /mnt
> >    du: mount point ‘/mnt/mnt’ already traversed
> >    0    /mnt
> >
> >    $ chown -R root  /mnt
> >    chown: 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/mnt’
> >
> > Just for the record, non-FTS ls(1) uses a different diagnostic:
> >
> >    $ ls -R /mnt
> >    /mnt:
> >    mnt
> >    ls: /mnt/mnt: not listing already-listed directory
> >
> > It seems that there is still room for improvement.
> >
> > Have a nice day,
> > Berny
>
> Hello all,
>
> After discussing further in RH BZ 1045086 
(http://rhn.redhat.com/errata/RHSA-2013-1652.htmlincludes), we I would like to 
discuss the following options with upstream for consistency.
>
> 1.  Ensure the new warning for du is upstream:  "mount point %s already 
traversed"

Already done with the above mentioned commit (cf7e1b5b).

> 2. Ensure the other commands are using the same message for consistency 
(chcon, chmod, chown-core, remove)
>
> 3. Evaluate if a separate exit code for this condition is appropriate. This 
would allow for slightly easier scripting to check for this condition and rule out 
any concerns that the warning message
> might change in the future.
>
> 4. Evaluate find, ls  - does it make sense for these to be consistent as well?
>
> After discussing here, I will likely submit a BZ for #2 in against RHEL.  And 
if all agree, I can submit a BZ for #3 and/or #4 as well.
>
> Thanks to all in advance for discussing this and helping us work this out.  I 
know it's a tedious topic.  I will also document this behavior for RHEL & Fedora 
to provide a final document to direct all
> future inquiries so that we can quit discussing it in the future!
> -Terry

I'd only go with #2, and probably look at ls(1).
I think it's not worth adding a new exit code (#3).
And find(1) is out of scope here - it's in findutils
(though it's probably worth looking).

I'll try to come up with a patch for #2 in the next days.

Have a nice day,
Berny