From: Hua Zhong Date: Mon, 15 May 2006 16:44:22 +0000 (-0700) Subject: [PATCH] fix can_share_swap_page() when !CONFIG_SWAP X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=e6333fd4ddf7a583480017f535b9ea53c116ab81;p=deliverable%2Flinux.git [PATCH] fix can_share_swap_page() when !CONFIG_SWAP can_share_swap_page() is used to check if the page has the last reference. This avoids allocating a new page for COW if it's the last page. However, if CONFIG_SWAP is not set, can_share_swap_page() is defined as 0, thus always causes a copy for the last COW page. The below simple patch fixes it. Signed-off-by: Hua Zhong Cc: David Howells Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/linux/swap.h b/include/linux/swap.h index 5b1fdf1cff4f..f03c24719302 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -296,7 +296,7 @@ static inline void disable_swap_token(void) #define read_swap_cache_async(swp,vma,addr) NULL #define lookup_swap_cache(swp) NULL #define valid_swaphandles(swp, off) 0 -#define can_share_swap_page(p) 0 +#define can_share_swap_page(p) (page_mapcount(p) == 1) #define move_to_swap_cache(p, swp) 1 #define move_from_swap_cache(p, i, m) 1 #define __delete_from_swap_cache(p) /*NOTHING*/