Check if the flag is already set before setting it, and vice versa
for clearing.
Obviously setting or clearing a flag twice isn't a problem on it's
own, but it implies that there's an issue where some piece of code
assumed an opposite state of the flag.
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
include/linux/page-flags.h | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index d1fe1a7..36b0bef 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -130,6 +130,12 @@ enum pageflags {
#ifndef __GENERATING_BOUNDS_H
+#ifdef CONFIG_DEBUG_VM_PAGE_FLAGS
+#define VM_ASSERT_FLAG(assert, page) VM_BUG_ON_PAGE(assert, page)
+#else
+#define VM_ASSERT_FLAG(assert, page) do { } while (0)
+#endif
+
/*
* Macros to create function definitions for page flags
*/
@@ -139,11 +145,13 @@ static inline int Page##uname(const struct page *page) \
#define SETPAGEFLAG(uname, lname) \
static inline void SetPage##uname(struct page *page) \
- { set_bit(PG_##lname, &page->flags); }
+ { VM_ASSERT_FLAG(Page##uname(page), page); \
+ set_bit(PG_##lname, &page->flags); }
#define CLEARPAGEFLAG(uname, lname) \
static inline void ClearPage##uname(struct page *page) \
- { clear_bit(PG_##lname, &page->flags); }
+ { VM_ASSERT_FLAG(!Page##uname(page), page); \
+ clear_bit(PG_##lname, &page->flags); }
#define __SETPAGEFLAG(uname, lname) \
static inline void __SetPage##uname(struct page *page) \
--
1.8.3.2
--
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