mm: Move nth_page from folio_page into folio_next

Commit Message

Herbert Xu March 13, 2025, 4:40 a.m. UTC

Discontiguous memory may require the use of nth_page instead of adding
to struct page arithmetically.  However, discontiguous memory cannot
exist within a single folio.

The function folio_page is mostly used for accessing a page within
a folio, therefore using nth_page for it is overkill.

Move it to the only place where it's needed, which is folio_next.

Signed-off-by: Herbert Xu <[e-mail]>

Patch

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7b1068ddcbb7..5f63ee0770f7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2115,7 +2115,7 @@  static inline int thp_nr_pages(struct page *page)
  */
 static inline struct folio *folio_next(struct folio *folio)
 {
-	return (struct folio *)folio_page(folio, folio_nr_pages(folio));
+	return (struct folio *)nth_page(&folio->page, folio_nr_pages(folio));
 }
 
 /**
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 36d283552f80..ebba355c45a5 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -275,7 +275,7 @@  static __always_inline unsigned long _compound_head(const struct page *page)
  * check that the page number lies within @folio; the caller is presumed
  * to have a reference to the page.
  */
-#define folio_page(folio, n)	nth_page(&(folio)->page, n)
+#define folio_page(folio, n)	(&(folio)->page + (n))
 
 static __always_inline int PageTail(const struct page *page)
 {