mm: Add folio_test_pmd_mappable()

Add a predicate to determine if the folio might be mapped by a PMD entry.
If CONFIG_TRANSPARENT_HUGEPAGE is disabled, we know it can't be, even
if it's large enough.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index f280f33ff223..e4c18ba8d3bf 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -274,6 +274,15 @@ static inline int thp_nr_pages(struct page *page)
 	return 1;
 }
 
+/**
+ * folio_test_pmd_mappable - Can we map this folio with a PMD?
+ * @folio: The folio to test
+ */
+static inline bool folio_test_pmd_mappable(struct folio *folio)
+{
+	return folio_order(folio) >= HPAGE_PMD_ORDER;
+}
+
 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 		pmd_t *pmd, int flags, struct dev_pagemap **pgmap);
 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
@@ -339,6 +348,11 @@ static inline int thp_nr_pages(struct page *page)
 	return 1;
 }
 
+static inline bool folio_test_pmd_mappable(struct folio *folio)
+{
+	return false;
+}
+
 static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
 {
 	return false;