Re: [PATCH 3/5] mm: export zap_page_range_single and list_lru_add/del

[David Hildenbrand (arm)]

On 2/5/26 12:57, Lorenzo Stoakes wrote:
> +cc Christoph for his input on exports here.
>
> On Thu, Feb 05, 2026 at 12:43:03PM +0100, David Hildenbrand (arm) wrote:
> > On 2/5/26 12:29, Lorenzo Stoakes wrote:
> > > Same point as before about exporting symbols, but given the _obj variants are
> > > exported already this one is more valid.
> > >
> > >
> > > Sorry but I don't want this exported at all.
> > >
> > > This is an internal implementation detail which allows fine-grained control of
> > > behaviour via struct zap_details (which binder doesn't use, of course :)
> >
> > I don't expect anybody to set zap_details, but yeah, it could be abused.
> > It could be abused right now from anywhere else in the kernel
> > where we don't build as a module :)
> >
> > Apparently we export a similar function in rust where we just removed the last parameter.
>
> What??
>
> Alice - can you confirm rust isn't exporting stuff that isn't explicitly marked
> EXPORT_SYMBOL*() for use by other rust modules?
>
> It's important we keep this in sync, otherwise rust is overriding kernel policy.
>
> > I think zap_page_range_single() is only called with non-NULL from mm/memory.c.
> >
> > So the following makes likely sense even outside of the context of this series:
>
> Yeah this looks good so feel free to add a R-b from me tag when you send it
> BUT...
>
> I'm still _very_ uncomfortable with exporting this just for binder which seems
> to be doing effectively mm tasks itself in a way that makes me think it needs a
> rework to not be doing that and to update core mm to add functionality if it's
> needed.
>
> In any case, if we _do_ export this I think I'm going to insist on this being
> EXPORT_SYMBOL_FOR_MODULES() _only_ for the binder in-tree module.

Works for me.

Staring at it again, I think I landed in cleanup land.

zap_vma_ptes() is exported and does the same thing as 
zap_page_range_single(), just with some additional safety checks.

Fun.


Let me cleanup. Good finger exercise after one month of almost-not coding :)

--
Cheers,

David