Commit e6333fd4 authored by Hua Zhong's avatar Hua Zhong Committed by Linus Torvalds

[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: default avatarHua Zhong <hzhong@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 41e5a6ac
......@@ -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*/
......
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