diff options
Diffstat (limited to 'include/linux/mm.h')
| -rw-r--r-- | include/linux/mm.h | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 679300c050f5..ff83798e1c27 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -402,16 +402,23 @@ static inline void init_page_count(struct page *page) /* * PageBuddy() indicate that the page is free and in the buddy system * (see mm/page_alloc.c). + * + * PAGE_BUDDY_MAPCOUNT_VALUE must be <= -2 but better not too close to + * -2 so that an underflow of the page_mapcount() won't be mistaken + * for a genuine PAGE_BUDDY_MAPCOUNT_VALUE. -128 can be created very + * efficiently by most CPU architectures. */ +#define PAGE_BUDDY_MAPCOUNT_VALUE (-128) + static inline int PageBuddy(struct page *page) { - return atomic_read(&page->_mapcount) == -2; + return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE; } static inline void __SetPageBuddy(struct page *page) { VM_BUG_ON(atomic_read(&page->_mapcount) != -1); - atomic_set(&page->_mapcount, -2); + atomic_set(&page->_mapcount, PAGE_BUDDY_MAPCOUNT_VALUE); } static inline void __ClearPageBuddy(struct page *page) |