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.
PAGE_MASK (and its HPAGE counterparts) always confuses me because it's
a mask which returns the upper bits rather than one which returns the
lower bits.
