mm: optimize get_scan_ratio for no swap

Rik suggests a simplified get_scan_ratio() for !CONFIG_SWAP.  Yes, the gcc
optimizer gives us that, when nr_swap_pages is #defined as 0L.  Move usual
declaration to swapfile.c: it never belonged in page_alloc.c.

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>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index c0d23ac710d5..3a31cc25bd2c 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -163,7 +163,6 @@ struct swap_list_t {
 /* linux/mm/page_alloc.c */
 extern unsigned long totalram_pages;
 extern unsigned long totalreserve_pages;
-extern long nr_swap_pages;
 extern unsigned int nr_free_buffer_pages(void);
 extern unsigned int nr_free_pagecache_pages(void);
 
@@ -291,6 +290,7 @@ extern struct page *swapin_readahead(swp_entry_t, gfp_t,
                         struct vm_area_struct *vma, unsigned long addr);
 
 /* linux/mm/swapfile.c */
+extern long nr_swap_pages;
 extern long total_swap_pages;
 extern void si_swapinfo(struct sysinfo *);
 extern swp_entry_t get_swap_page(void);
@@ -331,7 +331,8 @@ static inline void disable_swap_token(void)
 
 #else /* CONFIG_SWAP */
 
-#define total_swap_pages                        0
+#define nr_swap_pages                           0L
+#define total_swap_pages                        0L
 #define total_swapcache_pages                   0UL
 
 #define si_swapinfo(val) \