mm: move folio_set_compound_order() to mm/internal.h

folio_set_compound_order() is moved to an mm-internal location so external
folio users cannot misuse this function.  Change the name of the function
to folio_set_order() and use WARN_ON_ONCE() rather than BUG_ON.  Also,
handle the case if a non-large folio is passed and add clarifying comments
to the function.

Link: https://lore.kernel.org/lkml/[email protected]/T/
Link: https://lkml.kernel.org/r/[email protected]
Fixes: 9fd330582b2f ("mm: add folio dtor and order setter functions")
Signed-off-by: Sidhartha Kumar <[email protected]>
Suggested-by: Mike Kravetz <[email protected]>
Suggested-by: Muchun Song <[email protected]>
Suggested-by: Matthew Wilcox <[email protected]>
Suggested-by: John Hubbard <[email protected]>
Reviewed-by: John Hubbard <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 0 insertions, 16 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8f857163ac89..253b2d7489e6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1019,22 +1019,6 @@ static inline void set_compound_order(struct page *page, unsigned int order)
 #endif
 }
 
-/*
- * folio_set_compound_order is generally passed a non-zero order to
- * initialize a large folio.  However, hugetlb code abuses this by
- * passing in zero when 'dissolving' a large folio.
- */
-static inline void folio_set_compound_order(struct folio *folio,
-		unsigned int order)
-{
-	VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
-
-	folio->_folio_order = order;
-#ifdef CONFIG_64BIT
-	folio->_folio_nr_pages = order ? 1U << order : 0;
-#endif
-}
-
 /* Returns the number of pages in this potentially compound page. */
 static inline unsigned long compound_nr(struct page *page)
 {