On Tue, Jan 01, 2019 at 03:11:04PM -0500, Zi Yan wrote:
> On 1 Jan 2019, at 1:39, Matthew Wilcox wrote:
>
> > On Tue, Jan 01, 2019 at 02:02:22AM +0300, Kirill A. Shutemov wrote:
> >> On Mon, Dec 31, 2018 at 05:42:23AM -0800, Matthew Wilcox wrote:
> >>> It's unnecessarily hard to find out the size of a potentially huge page.
> >>> Replace 'PAGE_SIZE << compound_order(page)' with page_size(page).
> >>
> >> Good idea.
> >>
> >> Should we add page_mask() and page_shift() too?
> >
> > I'm not opposed to that at all. I also have a patch to add compound_nr():
> >
> > +/* Returns the number of pages in this potentially compound page. */
> > +static inline unsigned long compound_nr(struct page *page)
> > +{
> > + return 1UL << compound_order(page);
> > +}
> >
> > I just haven't sent it yet ;-) It should, perhaps, be called page_count()
> > or nr_pages() or something. That covers most of the remaining users of
> > compound_order() which look awkward.
>
> We already have hpage_nr_pages() to show the number of pages. Why do we need
> another one?
Not all compound pages are PMD sized.
