On Fri, Jun 05, 2015 at 01:07:15AM +0100, Al Viro wrote:
> Umm... Cosmetical point is that this
>
> > +static bool ovl_remote(struct dentry *root)
> > +{
> > + const struct dentry_operations *dop = root->d_op;
> > +
> > + return dop && (dop->d_revalidate || dop->d_weak_revalidate);
> > +}
>
> is better done as
> root->d_flags & (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE)
Okay.
>
> More interesting question is whether anything in the system relies on
> existing behaviour that follows ->d_revalidate() returning 0.
Hmm, d_invalidate() almost always follows ->d_revalidate(). Almost, becuase RCU
lookup can get aborted at that point. We can easily stick d_invalidate() in
there for the non-RCU case.
Regular lookup also almost always follows ->d_revalidate(). Except if
allocation of new dentry fails. So relying on this would be buggy (which is not
to say nobody does it).
> Have you tried to mount e.g. procfs as underlying layer and torture it for a
> while?
I did try now. Nothing bad happened during the test (parallel stat(1) of the
whole overlayed proc tree).
My laptop froze while trying to write this mail. But it's 8 years old and when
the fan starts to make noises and the weather is hot, it does this sometimes. I
don't think that has anything to do with overlayfs, but will do more testing...
Thanks,
Miklos
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