mm: Support arbitrary THP sizes

For code which has not yet been converted from THP to folios, use the
compound size of the page instead of assuming PTE or PMD size.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

include/linux/huge_mm.h

@@ -250,30 +250,6 @@ static inline spinlock_t *pud_trans_huge_lock(pud_t *pud,
 		return NULL;
 }
 
-/**
- * thp_order - Order of a transparent huge page.
- * @page: Head page of a transparent huge page.
- */
-static inline unsigned int thp_order(struct page *page)
-{
-	VM_BUG_ON_PGFLAGS(PageTail(page), page);
-	if (PageHead(page))
-		return HPAGE_PMD_ORDER;
-	return 0;
-}
-
-/**
- * thp_nr_pages - The number of regular pages in this huge page.
- * @page: The head page of a huge page.
- */
-static inline int thp_nr_pages(struct page *page)
-{
-	VM_BUG_ON_PGFLAGS(PageTail(page), page);
-	if (PageHead(page))
-		return HPAGE_PMD_NR;
-	return 1;
-}
-
 /**
  * folio_test_pmd_mappable - Can we map this folio with a PMD?
  * @folio: The folio to test
@@ -336,18 +312,6 @@ static inline struct list_head *page_deferred_list(struct page *page)
 #define HPAGE_PUD_MASK ({ BUILD_BUG(); 0; })
 #define HPAGE_PUD_SIZE ({ BUILD_BUG(); 0; })
 
-static inline unsigned int thp_order(struct page *page)
-{
-	VM_BUG_ON_PGFLAGS(PageTail(page), page);
-	return 0;
-}
-
-static inline int thp_nr_pages(struct page *page)
-{
-	VM_BUG_ON_PGFLAGS(PageTail(page), page);
-	return 1;
-}
-
 static inline bool folio_test_pmd_mappable(struct folio *folio)
 {
 	return false;
@@ -489,15 +453,4 @@ static inline int split_folio_to_list(struct folio *folio,
 	return split_huge_page_to_list(&folio->page, list);
 }
 
-/**
- * thp_size - Size of a transparent huge page.
- * @page: Head page of a transparent huge page.
- *
- * Return: Number of bytes in this page.
- */
-static inline unsigned long thp_size(struct page *page)
-{
-	return PAGE_SIZE << thp_order(page);
-}
-
 #endif /* _LINUX_HUGE_MM_H */

include/linux/mm.h

@@ -939,6 +939,37 @@ static inline unsigned int page_shift(struct page *page)
 	return PAGE_SHIFT + compound_order(page);
 }
 
+/**
+ * thp_order - Order of a transparent huge page.
+ * @page: Head page of a transparent huge page.
+ */
+static inline unsigned int thp_order(struct page *page)
+{
+	VM_BUG_ON_PGFLAGS(PageTail(page), page);
+	return compound_order(page);
+}
+
+/**
+ * thp_nr_pages - The number of regular pages in this huge page.
+ * @page: The head page of a huge page.
+ */
+static inline int thp_nr_pages(struct page *page)
+{
+	VM_BUG_ON_PGFLAGS(PageTail(page), page);
+	return compound_nr(page);
+}
+
+/**
+ * thp_size - Size of a transparent huge page.
+ * @page: Head page of a transparent huge page.
+ *
+ * Return: Number of bytes in this page.
+ */
+static inline unsigned long thp_size(struct page *page)
+{
+	return PAGE_SIZE << thp_order(page);
+}
+
 void free_compound_page(struct page *page);
 
 #ifdef CONFIG_MMU