Re: Regression for MS_MOVE on kernel v5.1

[Adding Eric to the cc list since he implemented MNT_LOCKED]

Linus Torvalds [off-list ref] wrote:

quoted

The commit changes the internal logic to lock mounts when propagating
mounts (user+)mount namespaces and - I believe - causes do_mount_move()
to fail at:

You mean 'do_move_mount()'.

quoted

if (old->mnt.mnt_flags & MNT_LOCKED)
        goto out;

If that's indeed the case we should either revert this commit (reverts
cleanly, just tested it) or find a fix.

Hmm.. I'm not entirely sure of the logic here, and just looking at
that commit 3bd045cc9c4b ("separate copying and locking mount tree on
cross-userns copies") doesn't make me go "Ahh" either.

Al? My gut feel is that we need to just revert, since this was in 5.1
and it's getting reasonably late in 5.2 too. But maybe you go "guys,
don't be silly, this is easily fixed with this one-liner".