On Sat, 12 Jun 2021, Matthew Wilcox wrote:
> On Fri, Jun 11, 2021 at 09:31:16PM -0700, Hugh Dickins wrote:
> > +++ linux/include/linux/pagemap.h 2021-06-11 17:30:28.726720252 -0700
> > @@ -516,8 +516,7 @@ static inline struct page *read_mapping_
> > }
> >
> > /*
> > - * Get index of the page with in radix-tree
> > - * (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE)
> > + * Get index of the page within radix-tree (but not for hugetlb pages).
> > */
>
> I think the TODO should be retained. It's still something that I
> intend to do.
Okay. I did not mean to imply, by removing those TODOs, that they
should not be done: just that they were a developer's notes to self,
that I found distracting there.
I've restored both TODOs (but changed the second to say
"hugetlb pages" explicitly, rather than the ambiguous "hugepage").
> > --- 5.13-rc5/mm/hugetlb.c 2021-06-06 16:57:26.263006733 -0700
> > +++ linux/mm/hugetlb.c 2021-06-11 17:30:28.730720276 -0700
> > @@ -1588,15 +1588,12 @@ struct address_space *hugetlb_page_mappi
> > return NULL;
> > }
> >
> > -pgoff_t __basepage_index(struct page *page)
> > +pgoff_t hugetlb_basepage_index(struct page *page)
> > {
> > struct page *page_head = compound_head(page);
> > pgoff_t index = page_index(page_head);
> > unsigned long compound_idx;
> >
> > - if (!PageHuge(page_head))
> > - return page_index(page);
> > -
> > if (compound_order(page_head) >= MAX_ORDER)
> > compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
> > else
> >
>
> urgh. this trailing bit should be:
>
> #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
> compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
> #else
> compound_idx = page - page_head;
> #endif
I don't see what's wrong with what's there, myself. Unfamiliar territory
to me, but mem_map_next() appears to have the same MAX_ORDER expectation.
Or perhaps you're just suggesting an optimization.
If it were obvious to me, I'd have gladly folded it in; but no,
please send your own patch for that, running it by Mike Kravetz
and Mike Rapoport and David Hildenbrand, I think.
Thanks, v2 follows,
Hugh
