Re: [PATCH] proc: fix mount -t proc -o AAA

[Andrew Morton]

On Sun, 25 Mar 2012 18:23:16 -0400
Valdis.Kletnieks@xxxxxx wrote:

> On Sun, 25 Mar 2012 19:36:12 +0400, Vasiliy Kulikov said:
> > On Sun, Mar 25, 2012 at 09:24 +0200, Arkadiusz MiEkiewicz wrote:
> > > but there is another problem - unmounting it and mounting without options
> > > causes old option to persist:
> > >
> > > # mount none /proc -t proc -o hidepid=2
> > > # umount /proc
> > > # mount none /proc -t proc
> > > # grep "/proc" /proc/mounts
> > > none /proc proc rw,relatime,hidepid=2 0 0
> > >
> > > There should be no hidepid=2 now.
> >
> > No, that's an expected behaviour.
> 
> "You keep using that word. I do not think it means what you think it means". ;)
> 
> > Procfs is a special filesystem.
> 
> And the fact it's "special" makes this *unexpected* behavior.  Are there
> any other filesystems where -o values will persist across an unmount
> and then take effect *even if no -o is given* on a subsequent mount?
> 
> Yes, it may be what the code actually *does*, but it certainly violates
> the Principle of Least Surprise...

It surprises me ;)  I never noticed that before.

It does seem pretty insane.  I wonder how much downstream damage would
result from fixing it.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/