[PATCH] Swap Migration V5: Add CONFIG_MIGRATION for page migration support

Include page migration if the system is NUMA or having a memory model that
allows distinct areas of memory (SPARSEMEM, DISCONTIGMEM).

And:
- Only include lru_add_drain_per_cpu if building for an SMP system.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 893096e..117add0 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -178,7 +178,9 @@
 extern int isolate_lru_page(struct page *p);
 extern int putback_lru_pages(struct list_head *l);
 
+#ifdef CONFIG_MIGRATION
 extern int migrate_pages(struct list_head *l, struct list_head *t);
+#endif
 
 #ifdef CONFIG_MMU
 /* linux/mm/shmem.c */