[PATCH v4 00/15] follow_pfn and other iomap races

[Christoph Hellwig]

On Thu, Oct 29, 2020 at 10:25:16AM +0100, Daniel Vetter wrote:
> On Thu, Oct 29, 2020 at 9:57 AM Christoph Hellwig <hch at infradead.org> wrote:
> >
> > Maybe I'm missing something, but shouldn't follow_pfn be unexported
> > at the end of the series?
> 
> kvm is a legit user and modular afaict. But since you can't use this
> without an mmu_notifier anyway (or digging around in pagetable
> locking), maybe it should be EXPORT_SYMBOL_GPL now at least?

I think it should then take the notifier as an argument even if it isn't
diretly used as a safety check, and get a new name describing it.

EXPORT_SYMBOL_GPL is probably ok for now, but I'm drafting a new
EXPORT_SYMBOL_FOR_MODULE() which will export symbols that can only be
used by one specific module, with kvm being a prime user due to all
the odd exports it requires that aren't really the kernel interface by
any normal means.