Re: mount -f regression in v2.21's new-mount

Karel Zak
2012-03-12T15:26:57Z

On Sun, Mar 11, 2012 at 07:06:26PM +0000, Matt Burgess wrote:
> On Fri, 2012-03-09 at 13:29 +0100, Karel Zak wrote:
> > On Fri, Mar 09, 2012 at 04:30:02AM -0700, Matthew Burgess wrote:
> > > On Fri, 9 Mar 2012 11:53:04 +0100, Karel Zak <kzak@redhat.com> wrote:
> > > > On Thu, Mar 08, 2012 at 08:25:00PM +0000, Matt Burgess wrote:
> > > >> I've attached LIBMOUNT_DEBUG output from the 'mount -a' call that our
> > > >> bootscript does. Note how mount correctly detects that /proc, /sys
> > > >
> > > > No, it calls mount(2) syscall for /proc. The problem is that the
> > > > detection code expects /proc/self/mountinfo (used on systems with
> > > > mtab -> /proc/mounts symlink), but your system uses regular mtab.
> > > >
> > > > I'll fix it. Thanks.
> >
> > Fixed, try git pull.
>
> Thanks, that's sorted it!
> >
> > > Thanks! Is there a consensus opinion on whether users should be
> > > using a regular mtab or a symlink to /proc/self/mountinfo?
> >
> > - disadvantage is that some userspace utils (e.g. df(1) are not able
> > to de-duplicate list of mounted filesystem (bind mounts))
> >
> > + advantage is that there is only one list of mounted filesystems
> > with always valid mount options (on systems with mtab is not problem
> > to have 'rw' in mtab for read-only NFS, etc.), no problems with
> > namespaces, not writable files in /etc, no mtab lock, etc.
> >
> > The symlink is required for systemd.
>
> Thanks for the info. Looks like there are more advantages than
> disadvantages. Without wishing to stray too far off-topic, do you know
> if the Coreutils folks are aware of/looking at the 'df' issue?

My wish:

- add FS de-duplicate function to libmount
- add SIZE, USE, AVAILABLE, USE% columns to findmnt
- add --df to findmnt
- try to implement df(1) compatible output if findmnt argv[0] is
df ;-)))

Karel

--
Karel Zak <kzak@redhat.com>