Messages in this thread | | | Date | Fri, 5 Jun 2015 17:37:29 +0200 | From | Miklos Szeredi <> | Subject | Re: [PATCH 2/2] ovl: allow distributed fs as lower layer |
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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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