[PATCH 8/8] mm: add add_to_swap stub

[Hugh Dickins <hugh@veritas.com>]

If we add a failing stub for add_to_swap(),
then we can remove the #ifdef CONFIG_SWAP from mm/vmscan.c.

This was intended as a source cleanup, but looking more closely, it turns
out that the !CONFIG_SWAP case was going to keep_locked for an anonymous
page, whereas now it goes to the more suitable activate_locked, like the
CONFIG_SWAP nr_swap_pages 0 case.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---
Shouldn't PageSwapBacked pages be made PageUnevictable
when CONFIG_UNEVICTABLE_LRU but !CONFIG_SWAP?

 include/linux/swap.h |    5 +++++
 mm/vmscan.c          |    2 --
 2 files changed, 5 insertions(+), 2 deletions(-)

--- swapfree7/include/linux/swap.h	2008-11-21 18:51:05.000000000 +0000
+++ swapfree8/include/linux/swap.h	2008-11-21 18:51:08.000000000 +0000
@@ -374,6 +374,11 @@ static inline struct page *lookup_swap_c
 	return NULL;
 }
 
+static inline int add_to_swap(struct page *page)
+{
+	return 0;
+}
+
 static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
 							gfp_t gfp_mask)
 {
--- swapfree7/mm/vmscan.c	2008-11-21 18:51:05.000000000 +0000
+++ swapfree8/mm/vmscan.c	2008-11-21 18:51:08.000000000 +0000
@@ -665,7 +665,6 @@ static unsigned long shrink_page_list(st
 					referenced && page_mapping_inuse(page))
 			goto activate_locked;
 
-#ifdef CONFIG_SWAP
 		/*
 		 * Anonymous process memory has backing store?
 		 * Try to allocate it some swap space here.
@@ -677,7 +676,6 @@ static unsigned long shrink_page_list(st
 				goto activate_locked;
 			may_enter_fs = 1;
 		}
-#endif /* CONFIG_SWAP */
 
 		mapping = page_mapping(page);
 

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