mm: remove set_compound_page_dtor()

All users can use the folio equivalent so this function can be safely
removed.

Link: https://lkml.kernel.org/r/20230612163405.99345-1-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Tarun Sahu <tsahu@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm.h

@@ -1223,16 +1223,6 @@ enum compound_dtor_id {
 };
 extern compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS];
 
-static inline void set_compound_page_dtor(struct page *page,
-		enum compound_dtor_id compound_dtor)
-{
-	struct folio *folio = (struct folio *)page;
-
-	VM_BUG_ON_PAGE(compound_dtor >= NR_COMPOUND_DTORS, page);
-	VM_BUG_ON_PAGE(!PageHead(page), page);
-	folio->_folio_dtor = compound_dtor;
-}
-
 static inline void folio_set_compound_dtor(struct folio *folio,
 		enum compound_dtor_id compound_dtor)
 {

mm/huge_memory.c

@@ -583,7 +583,7 @@ void prep_transhuge_page(struct page *page)
 
 	VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio);
 	INIT_LIST_HEAD(&folio->_deferred_list);
-	set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
+	folio_set_compound_dtor(folio, TRANSHUGE_PAGE_DTOR);
 }
 
 static inline bool is_transparent_hugepage(struct page *page)

mm/internal.h

@@ -391,7 +391,7 @@ static inline void prep_compound_head(struct page *page, unsigned int order)
 {
 	struct folio *folio = (struct folio *)page;
 
-	set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
+	folio_set_compound_dtor(folio, COMPOUND_PAGE_DTOR);
 	set_compound_order(page, order);
 	atomic_set(&folio->_entire_mapcount, -1);
 	atomic_set(&folio->_nr_pages_mapped, 0);