[PATCH v2 41/46] mm/page_alloc: Add folio allocation functions

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

The __alloc_folio(), __alloc_folio_node() and alloc_folio() functions
are mostly for type safety, but they also ensure that the page allocator
allocates a compound page and initialises the deferred list if the page
is large enough to have one.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/gfp.h | 16 ++++++++++++++++
 mm/mempolicy.c      | 10 ++++++++++
 mm/page_alloc.c     | 12 ++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index a503d928e684..76086c798cb1 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -511,6 +511,8 @@ static inline void arch_alloc_page(struct page *page, int order) { }
 
 struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
 		nodemask_t *nodemask);
+struct folio *__alloc_folio(gfp_t gfp, unsigned int order, int preferred_nid,
+		nodemask_t *nodemask);
 
 unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 				nodemask_t *nodemask, int nr_pages,
@@ -543,6 +545,15 @@ __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
 	return __alloc_pages(gfp_mask, order, nid, NULL);
 }
 
+static inline
+struct folio *__alloc_folio_node(gfp_t gfp, unsigned int order, int nid)
+{
+	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
+	VM_WARN_ON((gfp & __GFP_THISNODE) && !node_online(nid));
+
+	return __alloc_folio(gfp, order, nid, NULL);
+}
+
 /*
  * Allocate pages, preferring the node given as nid. When nid == NUMA_NO_NODE,
  * prefer the current CPU's closest node. Otherwise node must be valid and
@@ -559,6 +570,7 @@ 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 *alloc_folio(gfp_t gfp, unsigned order);
 extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
 			struct vm_area_struct *vma, unsigned long addr,
 			int node, bool hugepage);
@@ -569,6 +581,10 @@ static inline struct page *alloc_pages(gfp_t gfp_mask, unsigned int order)
 {
 	return alloc_pages_node(numa_node_id(), gfp_mask, order);
 }
+static inline struct folio *alloc_folio(gfp_t gfp, unsigned int order)
+{
+	return __alloc_folio_node(gfp, order, numa_node_id());
+}
 #define alloc_pages_vma(gfp_mask, order, vma, addr, node, false)\
 	alloc_pages(gfp_mask, order)
 #define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d79fa299b70c..382fec380f28 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2277,6 +2277,16 @@ struct page *alloc_pages(gfp_t gfp, unsigned order)
 }
 EXPORT_SYMBOL(alloc_pages);
 
+struct folio *alloc_folio(gfp_t gfp, unsigned order)
+{
+	struct page *page = alloc_pages(gfp | __GFP_COMP, order);
+
+	if (page && order > 1)
+		prep_transhuge_page(page);
+	return (struct folio *)page;
+}
+EXPORT_SYMBOL(alloc_folio);
+
 int vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst)
 {
 	struct mempolicy *pol = mpol_dup(vma_policy(src));
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6f2e131d08b5..b466d0aaaa18 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5225,6 +5225,18 @@ struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
 }
 EXPORT_SYMBOL(__alloc_pages);
 
+struct folio *__alloc_folio(gfp_t gfp, unsigned int order, int preferred_nid,
+		nodemask_t *nodemask)
+{
+	struct page *page = __alloc_pages(gfp | __GFP_COMP, order,
+			preferred_nid, nodemask);
+
+	if (page && order > 1)
+		prep_transhuge_page(page);
+	return (struct folio *)page;
+}
+EXPORT_SYMBOL(__alloc_folio);
+
 /*
  * Common helper functions. Never use with __GFP_HIGHMEM because the returned
  * address cannot represent highmem pages. Use alloc_pages and then kmap if
-- 
2.30.2