Re: Setting mount propagation type in new mount API

[Miklos Szeredi <mszeredi@redhat.com>]

On Fri, May 15, 2020 at 1:40 PM Michael Kerrisk (man-pages)
<mtk.manpages@gmail.com> wrote:
>
> Hello David, Miklos,
>
> I've been looking at the new mount API (fsopen(), fsconfig(),
> fsmount(), move_mount(), etc.) and among the details that remain
> mysterious to me is this: how does one set the propagation type
> (private/shared/slave/unbindable) of a new mount and change the
> propagation type of an existing mount?

Existing mount can be chaged with mount(NULL, path, NULL, MS_$(propflag), NULL).

To do that with a detached mount created by fsmount(2) the
"/proc/self/fd/$fd" trick can be used.

The plan was to introduce a mount_setattr(2) syscall, but that hasn't
happened yet...  I'm not sure we should be adding propagation flags to
fsmount(2), since that is a less generic mechanism than
mount_setattr(2) or just plain mount(2) as shown above.

Thanks,
Miklos