Commit e6333fd4 authored May 15, 2006 by Hua Zhong Committed by Linus Torvalds May 15, 2006

[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 <hzhong@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 41e5a6ac

include/linux/swap.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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/