Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote on 2013/04/17 02:37:40:
> Instead of bothering to store the index, why not just calculate it,
like:
>
> On 04/15/2013 08:37 PM, zhang.yi20@xxxxxxxxxx wrote:
> > +static inline int get_page_compound_index(struct page *page)
> > +{
> > + if (PageHead(page))
> > + return 0;
> > + return compound_head(page) - page;
> > +}
>
> BTW, you've really got to get your mail client fixed. Your patch is
> still line-wrapped.
I agree that I should calculate the compound index, but refer to
prep_compound_gigantic_page, I think it may like this:
+static inline int get_page_compound_index(struct page *page)
+{
+ struct page *head_page;
+ if (PageHead(page))
+ return 0;
+
+ head_page = compound_head(page);
+ if (compound_order(head_page) >= MAX_ORDER)
+ return page_to_pfn(page) - page_to_pfn(head_page);
+ else
+ return page - compound_head(page);
+}
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