forked from luck/tmp_suning_uos_patched
[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>
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@ -296,7 +296,7 @@ static inline void disable_swap_token(void)
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#define read_swap_cache_async(swp,vma,addr) NULL
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#define lookup_swap_cache(swp) NULL
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#define valid_swaphandles(swp, off) 0
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#define can_share_swap_page(p) 0
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#define can_share_swap_page(p) (page_mapcount(p) == 1)
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#define move_to_swap_cache(p, swp) 1
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#define move_from_swap_cache(p, i, m) 1
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#define __delete_from_swap_cache(p) /*NOTHING*/
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