mm: add add_to_swap stub

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>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Robin Holt <holt@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index c38bd157695b..c0d23ac710d5 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -371,6 +371,11 @@ static inline struct page *lookup_swap_cache(swp_entry_t swp)
         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)
 {
diff --git a/mm/vmscan.c b/mm/vmscan.c
index cc7401571cba..f350523a8eee 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -617,7 +617,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                                         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.
@@ -629,7 +628,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                                 goto activate_locked;
                         may_enter_fs = 1;
                 }
-#endif /* CONFIG_SWAP */
 
                 mapping = page_mapping(page);