bug#15986: df in current coreutils shows the device for loop mounts, not the file

[Linda Walsh]

On 28/11/2013 09:06, Bernhard Voelker wrote:
> tag 15986 notabug
> thanks
>
> On 11/28/2013 03:34 PM, Philipp Thomas wrote:
> > Df in older coreutils showed the file of a loop mount whereas currently it
> > shows you the loop device. This is IMHO bogus as what good is that info?
> >
> > Is this a deliberate change or a side effect of other changes? I searched
> > ChangeLog but didn't find anything relating to it (at least in my eyes).
>
> Hi Philipp,
>
> on systems where /etc/mtab is a regular file, 'mount' writes the name of
> the backing file into /etc/mtab.
> Nowadays, as /etc/mtab is a symlink to /proc/self/mounts, this information
> is not available to 'df' anymore**.
----

The fact that /etc/mtab is pointing to a wrongly formatted file by
default, these days, rather than being used to store user-specific mount
information, seems to be getting well-used as a reason for dropping
useful information:

(** ex: -showing the user their real "root" instead of /root,
 --     -showing the user modified  device names instead of
        what they passed to mount (i.e. showing
/dev/mapper/Hns-Home-users--  instead of /dev/HnS/Home/users-home
        - showing what options they specified rather than all
that applied at the time of mount, like:
   /dev/mapper/Backups-Backups on /backups type xfs (rw,nodiratime,relatime,\
    swalloc,attr2,largeio,inode64,allocsize=131072k,logbsize=256k,sunit=128,\
    swidth=1536,noquota)
instead of:
    /dev/Backups/Backups  /backups  xfs\
    defaults,nodiratime,swalloc,largeio,logbsize=256k,\
    inode64,allocsize=128m 2 0

Maybe if they want to substitute /etc/mtab for /proc/mounts, they should have
wondered a bit more where to get the correct information to allow for backwards
compat (I know there are other utils and /proc locations to get access to the
device you want, BUT -- they are not standard locations.  Should all of the 
linux
utils have to jump through hoops to provide relevant and accurate information as
specified by the user?