Re: devfs vs udev, thoughts from a devfs user

dleonard
2004-02-11T19:19:44Z

For mount 2.12 /etc/mtab doesn't get updated correctly but umount is at least smart (or dumb) enough not to do the wrong thing.

r:dryad:/tmp# mkdir /tmp/a /tmp/b
r:dryad:/tmp# mount -t ramfs none /tmp/a
r:dryad:/tmp# touch /tmp/a/foo
r:dryad:/tmp# mount --move /tmp/a /tmp/b
r:dryad:/tmp# ls /tmp/b
foo

r:dryad:/tmp# cat /etc/mtab
/dev/hda2 / ext3 rw,errors=remount-ro 0 0
proc /proc proc rw 0 0
devpts /dev/pts devpts rw,gid=5,mode=620 0 0
/dev/hda5 /usr ext3 rw 0 0
/dev/hda6 /home ext3 rw 0 0
usbfs /proc/bus/usb usbfs rw 0 0
none /tmp/a ramfs rw 0 0
/tmp/a /tmp/b none rw 0 0

r:dryad:/tmp# cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/root / ext3 rw 0 0
proc /proc proc rw 0 0
devpts /dev/pts devpts rw 0 0
/dev/hda5 /usr ext3 rw 0 0
/dev/hda6 /home ext3 rw 0 0
usbfs /proc/bus/usb usbfs rw 0 0
none /tmp/b ramfs rw 0 0

r:dryad:/tmp# umount /tmp/a
umount: none: not found
umount: /tmp/a: not mounted
umount: none: not found
umount: /tmp/a: not mounted
r:dryad:/tmp# ls /tmp/b
foo

This problem *does* occur exactly as Greg says with mount 2.11n (debian) though.

--

<Douglas Leonard>
<dleonard@dleonard.net>

On Wed, 11 Feb 2004, Bill Rugolsky Jr. wrote:

> On Wed, Feb 11, 2004 at 07:50:49AM +0000, viro@parcelfarce.linux.theplanet.co.uk wrote:
> > On Tue, Feb 10, 2004 at 05:16:00PM -0800, Greg KH wrote:
> > > Doesn't work for what we want here:
> > >
> > > $ mkdir /tmp/a /tmp/b
> > > $ mount -t ramfs none /tmp/a
> > > $ touch /tmp/a/foo
> > > $ mount --move /tmp/a /tmp/b
> > > $ ls /tmp/b
> > > foo
> > > $ umount /tmp/a
> > > $ ls /tmp/b
> > > $
> > >
> > > Hm, not nice :(
> >
> > Huh? Is that a bug report or just your guess at what would happen if you
> > tried the above?
> >
> > If it _does_ happen - we have a problem and I'd like to know which versions
> > have such bug.
>
> Ugh, /etc/mtab really ought to die.
>
> Anyway, with traditional /etc/mtab, mount --move produces:
>
> none on /tmp/a type ramfs (rw)
> /tmp/a on /tmp/b type none (rw)
>
> ln -sf /proc/self/mounts /etc/mtab and retry, it works fine:
>
> none on /tmp/b type ramfs (rw)
>
> I'll have a look at mount later today, if nobody else gets there first.
>
> -Bill
> -
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