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

From: Arkadiusz MiÅkiewicz
Date: Sun Mar 25 2012 - 13:41:42 EST

On Sunday 25 of March 2012, Vasiliy Kulikov wrote:
> On Sun, Mar 25, 2012 at 09:24 +0200, Arkadiusz MiÅkiewicz 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.
> Procfs is a special filesystem. Mount options are not reset on each
> mount(2) as you can mount procfs multiple times at different mount points
> (/proc/, /aaa/proc/, etc.). Each time you add mount options they are
> applied to _each_ mount point because there is no per-mount point sb, but
> there is a per pid_ns superblock: pid_ns itself. All options are stored
> at pid_ns.
> When you mount it another time without any option nothing should change
> at the old mount points. When you umount the last mount point all mount
> options are still stored. When you mount it again old options are used
> (unless you override them).

I wonder if it should support noxx options then (like nogid, nohidepid) ?

Arkadiusz MiÅkiewicz PLD/Linux Team
arekm /
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