On Fri, Jan 20, 2023 at 04:45:17AM +0000, Al Viro wrote:
> On Fri, Jan 20, 2023 at 04:28:12AM +0000, Matthew Wilcox wrote:
> > On Fri, Jan 20, 2023 at 04:21:06AM +0000, Al Viro wrote:
> > > On Thu, Jan 19, 2023 at 04:32:32PM +0100, Fabio M. De Francesco wrote:
> > >
> > > > -inline void dir_put_page(struct page *page)
> > > > +inline void dir_put_page(struct page *page, void *page_addr)
> > > > {
> > > > - kunmap(page);
> > > > + kunmap_local(page_addr);
> > >
> > > ... and that needed to be fixed - at some point "round down to beginning of
> > > page" got lost in rebasing...
> >
> > You don't need to round down in kunmap(). See:
> >
> > void kunmap_local_indexed(const void *vaddr)
> > {
> > unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
> >
>
> Sure, but... there's also this:
>
> static inline void __kunmap_local(const void *addr)
> {
> #ifdef ARCH_HAS_FLUSH_ON_KUNMAP
> kunmap_flush_on_unmap(addr);
> #endif
> }
>
> Are you sure that the guts of that thing will be happy with address that is not
> page-aligned? I've looked there at some point, got scared of parisc (IIRC)
> MMU details and decided not to rely upon that...
Ugh, PA-RISC (the only implementor) definitely will flush the wrong
addresses. I think we should do this, as having bugs that only manifest
on one not-well-tested architecture seems Bad.
static inline void __kunmap_local(const void *addr)
{
#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
- kunmap_flush_on_unmap(addr);
+ kunmap_flush_on_unmap(PAGE_ALIGN_DOWN(addr));
#endif
}
Thoughts?
