If you pass a const pointer to compound_head(), you get a const pointer
back; if you pass a mutable pointer, you get a mutable pointer back.
Also remove an unnecessary forward definition of struct page; we're about
to dereference page->compound_head, so it must already have been defined.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
include/linux/page-flags.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 04a34c08e0a6..d8e26243db25 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -177,17 +177,17 @@ enum pageflags {
#ifndef __GENERATING_BOUNDS_H
-struct page; /* forward declaration */
-
-static inline struct page *compound_head(struct page *page)
+static inline unsigned long _compound_head(const struct page *page)
{
unsigned long head = READ_ONCE(page->compound_head);
if (unlikely(head & 1))
- return (struct page *) (head - 1);
- return page;
+ return head - 1;
+ return (unsigned long)page;
}
+#define compound_head(page) ((typeof(page))_compound_head(page))
+
static __always_inline int PageTail(struct page *page)
{
return READ_ONCE(page->compound_head) & 1;
--
2.30.2
