mm: Add vma_alloc_folio()

This wrapper around alloc_pages_vma() calls prep_transhuge_page(),
removing the obligation from the caller.  This is in the same spirit
as __folio_alloc().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

include/linux/gfp.h

@@ -613,9 +613,11 @@ static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
 #ifdef CONFIG_NUMA
 struct page *alloc_pages(gfp_t gfp, unsigned int order);
 struct folio *folio_alloc(gfp_t gfp, unsigned order);
-extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
+struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
 			struct vm_area_struct *vma, unsigned long addr,
 			bool hugepage);
+struct folio *vma_alloc_folio(gfp_t gfp, int order, struct vm_area_struct *vma,
+		unsigned long addr, bool hugepage);
 #define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
 	alloc_pages_vma(gfp_mask, order, vma, addr, true)
 #else
@@ -627,8 +629,10 @@ static inline struct folio *folio_alloc(gfp_t gfp, unsigned int order)
 {
 	return __folio_alloc_node(gfp, order, numa_node_id());
 }
-#define alloc_pages_vma(gfp_mask, order, vma, addr, false)\
+#define alloc_pages_vma(gfp_mask, order, vma, addr, hugepage) \
 	alloc_pages(gfp_mask, order)
+#define vma_alloc_folio(gfp, order, vma, addr, hugepage)		\
+	folio_alloc(gfp, order)
 #define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
 	alloc_pages(gfp_mask, order)
 #endif

mm/mempolicy.c

@@ -2227,6 +2227,19 @@ struct page *alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 }
 EXPORT_SYMBOL(alloc_pages_vma);
 
+struct folio *vma_alloc_folio(gfp_t gfp, int order, struct vm_area_struct *vma,
+		unsigned long addr, bool hugepage)
+{
+	struct folio *folio;
+
+	folio = (struct folio *)alloc_pages_vma(gfp, order, vma, addr,
+			hugepage);
+	if (folio && order > 1)
+		prep_transhuge_page(&folio->page);
+
+	return folio;
+}
+
 /**
  * alloc_pages - Allocate pages.
  * @gfp: GFP flags.