[PATCHv3, RFC 08/34] thp, mm: introduce mapping_can_have_hugepages() predicate

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

Returns true if mapping can have huge pages. Just check for __GFP_COMP
in gfp mask of the mapping for now.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 include/linux/pagemap.h |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index e3dea75..56debde 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -84,6 +84,17 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
 				(__force unsigned long)mask;
 }
 
+static inline bool mapping_can_have_hugepages(struct address_space *m)
+{
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+		gfp_t gfp_mask = mapping_gfp_mask(m);
+		/* __GFP_COMP is key part of GFP_TRANSHUGE */
+		return !!(gfp_mask & __GFP_COMP);
+	}
+
+	return false;
+}
+
 /*
  * The page cache can done in larger chunks than
  * one page, because it allows for more efficient
-- 
1.7.10.4