From: Nick Piggin atomic_add_unless (atomic_inc_not_zero) no longer requires an offset refcount to function correctly. Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton --- include/linux/mm.h | 19 +++++-------------- 1 files changed, 5 insertions(+), 14 deletions(-) diff -puN include/linux/mm.h~mm-de-skew-page-refcounting include/linux/mm.h --- devel/include/linux/mm.h~mm-de-skew-page-refcounting 2006-02-07 18:25:53.000000000 -0800 +++ devel-akpm/include/linux/mm.h 2006-02-07 18:26:23.000000000 -0800 @@ -286,15 +286,6 @@ struct page { * * Also, many kernel routines increase the page count before a critical * routine so they can be sure the page doesn't go away from under them. - * - * Since 2.6.6 (approx), a free page has ->_count = -1. This is so that we - * can use atomic_add_negative(-1, page->_count) to detect when the page - * becomes free and so that we can also use atomic_inc_and_test to atomically - * detect when we just tried to grab a ref on a page which some other CPU has - * already deemed to be freeable. - * - * NO code should make assumptions about this internal detail! Use the provided - * macros which retain the old rules: page_count(page) == 0 is a free page. */ /* @@ -303,8 +294,8 @@ struct page { */ static inline int put_page_testzero(struct page *page) { - BUG_ON(atomic_read(&page->_count) == -1); - return atomic_add_negative(-1, &page->_count); + BUG_ON(atomic_read(&page->_count) == 0); + return atomic_dec_and_test(&page->_count); } /* @@ -313,10 +304,10 @@ static inline int put_page_testzero(stru */ static inline int get_page_unless_zero(struct page *page) { - return atomic_add_unless(&page->_count, 1, -1); + return atomic_inc_not_zero(&page->_count); } -#define set_page_count(p,v) atomic_set(&(p)->_count, (v) - 1) +#define set_page_count(p,v) atomic_set(&(p)->_count, (v)) #define __put_page(p) atomic_dec(&(p)->_count) extern void FASTCALL(__page_cache_release(struct page *)); @@ -325,7 +316,7 @@ static inline int page_count(struct page { if (PageCompound(page)) page = (struct page *)page_private(page); - return atomic_read(&page->_count) + 1; + return atomic_read(&page->_count); } static inline void get_page(struct page *page) _