[PATCH v4 21/36] mm: Add __page_cache_alloc_order

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>

This new function allows page cache pages to be allocated that are
larger than an order-0 page.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 include/linux/pagemap.h | 24 +++++++++++++++++++++---
 mm/filemap.c            | 12 ++++++++----
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index c75d7fb7ccbc..97f36ea16116 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -239,15 +239,33 @@ static inline int page_cache_add_speculative(struct page *page, int count)
 	return __page_cache_add_speculative(page, count);
 }
 
+static inline gfp_t thp_gfpmask(gfp_t gfp)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	/* We'd rather allocate smaller pages than stall a page fault */
+	gfp |= GFP_TRANSHUGE_LIGHT;
+	gfp &= ~__GFP_DIRECT_RECLAIM;
+#endif
+	return gfp;
+}
+
 #ifdef CONFIG_NUMA
-extern struct page *__page_cache_alloc(gfp_t gfp);
+extern struct page *__page_cache_alloc_order(gfp_t gfp, unsigned int order);
 #else
-static inline struct page *__page_cache_alloc(gfp_t gfp)
+static inline
+struct page *__page_cache_alloc_order(gfp_t gfp, unsigned int order)
 {
-	return alloc_pages(gfp, 0);
+	if (order == 0)
+		return alloc_pages(gfp, 0);
+	return prep_transhuge_page(alloc_pages(thp_gfpmask(gfp), order));
 }
 #endif
 
+static inline struct page *__page_cache_alloc(gfp_t gfp)
+{
+	return __page_cache_alloc_order(gfp, 0);
+}
+
 static inline struct page *page_cache_alloc(struct address_space *x)
 {
 	return __page_cache_alloc(mapping_gfp_mask(x));
diff --git a/mm/filemap.c b/mm/filemap.c
index 23a051a7ef0f..9abba062973a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -941,24 +941,28 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
 
 #ifdef CONFIG_NUMA
-struct page *__page_cache_alloc(gfp_t gfp)
+struct page *__page_cache_alloc_order(gfp_t gfp, unsigned int order)
 {
 	int n;
 	struct page *page;
 
+	if (order > 0)
+		gfp = thp_gfpmask(gfp);
+
 	if (cpuset_do_page_mem_spread()) {
 		unsigned int cpuset_mems_cookie;
 		do {
 			cpuset_mems_cookie = read_mems_allowed_begin();
 			n = cpuset_mem_spread_node();
-			page = __alloc_pages_node(n, gfp, 0);
+			page = __alloc_pages_node(n, gfp, order);
+			prep_transhuge_page(page);
 		} while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
 
 		return page;
 	}
-	return alloc_pages(gfp, 0);
+	return prep_transhuge_page(alloc_pages(gfp, order));
 }
-EXPORT_SYMBOL(__page_cache_alloc);
+EXPORT_SYMBOL(__page_cache_alloc_order);
 #endif
 
 /*
-- 
2.26.2