Automatic deletion of loopback device upon umount?

[Rich Felker]

On Sun, Apr 15, 2012 at 05:18:08PM +0200, Florian Fainelli wrote:
> Le 07/04/2012 01:18, Rob Landley a écrit :
> >On 04/06/2012 01:20 AM, ralda at gmx.de wrote:
> >>Hi Florian !
> >>
> >>>1) loopback mount "foo" to mount /bar
> >>>2) umount /bar
> >>>3) append new files and re-generate the "foo" cramfs image
> >>>4) loopback mount "foo" to mount /bar
> >>>5) the contents of /bar are the same as in 1) and not 3)
> >>
> >>>Obviously using umount -d in 2) fixes the issue, but I was wondering
> >>>whether it would not be preferable to unconditionnaly delete the
> >>>loopback device upon umount? util-linux does this actually, so other
> >>>users might also be puzzled by such a case.
> >>
> >>I hit that too, some time ago, not cramfs but squashfs and ISO images.
> >>That was the reason I added an "alias umount='umount -d'" to
> >>my /etc/profile and added the "-d" to all umounts in scripts.
> >>
> >>IMHO it would be better to reverse definition of the "-d" option to
> >>umount and do NOT delete the loop device if option gets specified and
> >>drop/delete it in the default case.
> >
> >You mean the way I originally wrote it before this commit broke it?
> >
> >b2e578a1f2c3cf317b391a7d2c059d6a5f5368b8 is the first bad commit
> >commit b2e578a1f2c3cf317b391a7d2c059d6a5f5368b8
> >Author: Denis Vlasenko<vda.linux at googlemail.com>
> >Date:   Thu Feb 14 12:00:21 2008 +0000
> >
> >     umount: instead of non-standard -D, use -d with opposite meaning
> >       (closes bug 1604)
> >
> >I have no idea what bug 1604 was, but leaking loopback devices was
> >wrong.  I had code to automatically clean them up, it ran by default,
> >and now it doesn't.
> 
> Denys, what do you think about this? I agree with Rob here, not
> having the loopback deleted by default is definitively confusing.

I agree with Rob too, at least this once.. ;-)

Rich