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authorHua Zhong <hzhong@gmail.com>2006-05-15 09:44:22 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-05-15 11:20:56 -0700
commite6333fd4ddf7a583480017f535b9ea53c116ab81 (patch)
treedf1aeae28ce51103a0c9eda8f7d40e463297b2ef
parent41e5a6ac80c600e1f8bda0a4871f0b797e097d78 (diff)
downloadlinux-e6333fd4ddf7a583480017f535b9ea53c116ab81.tar.gz
[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>
-rw-r--r--include/linux/swap.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 5b1fdf1cff4..f03c2471930 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*/