Re: [GIT PULL] overlayfs updates for 6.13

[Christian Brauner]

On Sat, Nov 23, 2024 at 01:06:14PM +0100, Christian Brauner wrote:
> On Fri, Nov 22, 2024 at 09:21:58PM -0800, Linus Torvalds wrote:
> > On Fri, 22 Nov 2024 at 01:57, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> > >
> > > - Introduction and use of revert/override_creds_light() helpers, that were
> > >   suggested by Christian as a mitigation to cache line bouncing and false
> > >   sharing of fields in overlayfs creator_cred long lived struct cred copy.
> > 
> > So I don't actively hate this, but I do wonder if this shouldn't have
> > been done differently.
> > 
> > In particular, I suspect *most* users of override_creds() actually
> > wants this "light" version, because they all already hold a ref to the
> > cred that they want to use as the override.
> > 
> > We did it that safe way with the extra refcount not because most
> > people would need it, but it was expected to not be a big deal.
> > 
> > Now you found that it *is* a big deal, and instead of just fixing the
> > old interface, you create a whole new interface and the mental burden
> > of having to know the difference between the two.
> 
> > So may I ask that you look at perhaps just converting the (not very
> > many) users of the non-light cred override to the "light" version?
> 
> I think that could be a good idea in general.
> 
> But I have to say I'm feeling a bit defensive after having read your
> message even though I usually try not to. :) 

It was just pointed out to me that this was written like I'm not reading
you messages - which is obviously not the case. What I means it that I
usually try to not be defensive when valid criticism is brought up. :)