On Mon, 2005-01-17 at 09:32, J. Bruce Fields wrote:
> On Mon, Jan 17, 2005 at 06:11:50AM +0000, Al Viro wrote:
> > No - I have been missing a typo. Make that "if mountpoint of what we
> > are moving...".
>
> OK, got it, so the point is that its not clear how you'd propagate the
> removal of the subtree from the vfsmount of the source mountpoint.
>
> By the way, I wrote up some notes this weekend in an attempt to explain
> the shared subtrees RFC to myself. They may or may not be helpful to
> anyone else:
>
> http://www.fieldses.org/~bfields/kernel/viro_mount_propagation.txt
Question 1:
If there exists a private subtree in a larger shared subtree, what
happens when the larger shared subtree is rbound to some other place?
Is a new private subtree created in the new larger shared subtree? or
will that be pruned out in the new larger subtree?
Concrete example:
mount <device1> /tmp/mnt1
mount <device2> /tmp/mnt1/mnt1.1
mount <device3> /tmp/mnt1/mnt1.1/mnt1.1.1
make --make-shared /tmp/mnt1
mount --make-private /tmp/mnt1/mnt1.1
make --rbind /tmp/mnt1 /tmp/mnt2
Question: will I see the mount at /tmp/mnt2/mnt1.1/mnt1.1.1 ?
My guess is since /tmp/mnt1/mnt1.1 is private that subtree
should not be even seen under /tmp/mnt2/mnt1.1 , Is that
the case? Or does the subtree get mirrored in /tmp/mnt2/mnt1.1;
however propogation is not set between the vfsstruct of
/mnt/mnt1/mnt1.1 and /mnt/mnt2/mnt1.1 ?
I believe its the former case.
Question 2:
When a mount gets propogated to a slave, but the slave
has mounted something else at the same place, and hence
that mount point is masked, what will happen?
Concrete example:
mount <device1> /tmp/mnt1
mkdir -p /tmp/mnt1/a/b
mount --rbind /tmp/mnt1 /tmp/mnt2
mount --make-slave /tmp/mnt2
mount <device2> /tmp/mnt2/a
rm -f /tmp/mnt2/a/*
what happens when a mount is attempted on /tmp/mnt1/a/b?
will that be reflected in /tmp/mnt2/a ?
I believe the answer is 'no', because that part of the subtree
in /tmp/mnt2 no more mirrors its parent subtree.
RP
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