[PATCH 5.4 65/78] mm: add thp_order

[Greg Kroah-Hartman]

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

commit 6ffbb45826f5d9ae09aa60cd88594b7816c96190 upstream

This function returns the order of a transparent huge page.  It compiles
to 0 if CONFIG_TRANSPARENT_HUGEPAGE is disabled.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20200629151959.15779-4-willy@xxxxxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 include/linux/huge_mm.h |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -231,6 +231,19 @@ static inline spinlock_t *pud_trans_huge
 	else
 		return NULL;
 }
+
+/**
+ * thp_order - Order of a transparent huge page.
+ * @page: Head page of a transparent huge page.
+ */
+static inline unsigned int thp_order(struct page *page)
+{
+	VM_BUG_ON_PGFLAGS(PageTail(page), page);
+	if (PageHead(page))
+		return HPAGE_PMD_ORDER;
+	return 0;
+}
+
 static inline int hpage_nr_pages(struct page *page)
 {
 	if (unlikely(PageTransHuge(page)))
@@ -290,6 +303,12 @@ static inline struct list_head *page_def
 #define HPAGE_PUD_MASK ({ BUILD_BUG(); 0; })
 #define HPAGE_PUD_SIZE ({ BUILD_BUG(); 0; })
 
+static inline unsigned int thp_order(struct page *page)
+{
+	VM_BUG_ON_PGFLAGS(PageTail(page), page);
+	return 0;
+}
+
 #define hpage_nr_pages(x) 1
 
 static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)