Re: [PATCH v1 2/3] overlay: Add the ability to remount volatile directories when safe

[Sargun Dhillon <sargun@sargun.me>]

On Wed, Nov 25, 2020 at 10:17 AM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> On Wed, Nov 25, 2020 at 02:46:20AM -0800, Sargun Dhillon wrote:
>
> [..]
> > @@ -1125,16 +1183,19 @@ static int ovl_workdir_cleanup_recurse(struct path *path, int level)
> >                       if (p->len == 2 && p->name[1] == '.')
> >                               continue;
> >               } else if (incompat) {
> > -                     pr_err("overlay with incompat feature '%s' cannot be mounted\n",
> > -                             p->name);
> > -                     err = -EINVAL;
> > -                     break;
> > +                     err = ovl_check_incompat(ofs, p, path);
> > +                     if (err < 0)
> > +                             break;
> > +                     /* Skip cleaning this */
> > +                     if (err == 1)
> > +                             continue;
> >               }
>
> Shouldn't we clean volatile/dirty on non-volatile mount. I did a
> volatile mount followed by a non-volatile remount and I still
> see work/incompat/volatile/dirty and "trusted.overlay.volatile" xattr
> on "volatile" dir. I would expect that this will be all cleaned up
> as soon as that upper/work is used for non-volatile mount.
>
>

Amir pointed out this is incorrect behaviour earlier.
You should be able to go:
non-volatile -> volatile
volatile -> volatile

But never
volatile -> non-volatile, since our mechanism is not bulletproof.

I will fix this in the next respin.