mm: convert is_transparent_hugepage() to use a folio

Replace a use of page->compound_dtor with its folio equivalent.

Link: https://lkml.kernel.org/r/20230111142915.1001531-20-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/huge_memory.c

@@ -591,12 +591,14 @@ void prep_transhuge_page(struct page *page)
 
 static inline bool is_transparent_hugepage(struct page *page)
 {
+	struct folio *folio;
+
 	if (!PageCompound(page))
 		return false;
 
-	page = compound_head(page);
-	return is_huge_zero_page(page) ||
-	       page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
+	folio = page_folio(page);
+	return is_huge_zero_page(&folio->page) ||
+	       folio->_folio_dtor == TRANSHUGE_PAGE_DTOR;
 }
 
 static unsigned long __thp_get_unmapped_area(struct file *filp,