[PATCH] SwapMig: CONFIG_MIGRATION fixes

Move move_to_lru, putback_lru_pages and isolate_lru in section surrounded by
CONFIG_MIGRATION saving some codesize for single processor kernels.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/swap.h

@@ -175,10 +175,9 @@ extern int try_to_free_pages(struct zone **, gfp_t);
 extern int shrink_all_memory(int);
 extern int vm_swappiness;
 
+#ifdef CONFIG_MIGRATION
 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
 

mm/vmscan.c

@@ -569,6 +569,40 @@ static int shrink_list(struct list_head *page_list, struct scan_control *sc)
 }
 
 #ifdef CONFIG_MIGRATION
+static inline void move_to_lru(struct page *page)
+{
+	list_del(&page->lru);
+	if (PageActive(page)) {
+		/*
+		 * lru_cache_add_active checks that
+		 * the PG_active bit is off.
+		 */
+		ClearPageActive(page);
+		lru_cache_add_active(page);
+	} else {
+		lru_cache_add(page);
+	}
+	put_page(page);
+}
+
+/*
+ * Add isolated pages on the list back to the LRU
+ *
+ * returns the number of pages put back.
+ */
+int putback_lru_pages(struct list_head *l)
+{
+	struct page *page;
+	struct page *page2;
+	int count = 0;
+
+	list_for_each_entry_safe(page, page2, l, lru) {
+		move_to_lru(page);
+		count++;
+	}
+	return count;
+}
+
 /*
  * swapout a single page
  * page is locked upon entry, unlocked on exit
@@ -709,6 +743,48 @@ int migrate_pages(struct list_head *l, struct list_head *t)
 
 	return nr_failed + retry;
 }
+
+static void lru_add_drain_per_cpu(void *dummy)
+{
+	lru_add_drain();
+}
+
+/*
+ * Isolate one page from the LRU lists and put it on the
+ * indicated list. Do necessary cache draining if the
+ * page is not on the LRU lists yet.
+ *
+ * Result:
+ *  0 = page not on LRU list
+ *  1 = page removed from LRU list and added to the specified list.
+ * -ENOENT = page is being freed elsewhere.
+ */
+int isolate_lru_page(struct page *page)
+{
+	int rc = 0;
+	struct zone *zone = page_zone(page);
+
+redo:
+	spin_lock_irq(&zone->lru_lock);
+	rc = __isolate_lru_page(page);
+	if (rc == 1) {
+		if (PageActive(page))
+			del_page_from_active_list(zone, page);
+		else
+			del_page_from_inactive_list(zone, page);
+	}
+	spin_unlock_irq(&zone->lru_lock);
+	if (rc == 0) {
+		/*
+		 * Maybe this page is still waiting for a cpu to drain it
+		 * from one of the lru lists?
+		 */
+		rc = schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
+		if (rc == 0 && PageLRU(page))
+			goto redo;
+	}
+	return rc;
+}
 #endif
 
 /*
@@ -758,48 +834,6 @@ static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
 	return nr_taken;
 }
 
-static void lru_add_drain_per_cpu(void *dummy)
-{
-	lru_add_drain();
-}
-
-/*
- * Isolate one page from the LRU lists and put it on the
- * indicated list. Do necessary cache draining if the
- * page is not on the LRU lists yet.
- *
- * Result:
- *  0 = page not on LRU list
- *  1 = page removed from LRU list and added to the specified list.
- * -ENOENT = page is being freed elsewhere.
- */
-int isolate_lru_page(struct page *page)
-{
-	int rc = 0;
-	struct zone *zone = page_zone(page);
-
-redo:
-	spin_lock_irq(&zone->lru_lock);
-	rc = __isolate_lru_page(page);
-	if (rc == 1) {
-		if (PageActive(page))
-			del_page_from_active_list(zone, page);
-		else
-			del_page_from_inactive_list(zone, page);
-	}
-	spin_unlock_irq(&zone->lru_lock);
-	if (rc == 0) {
-		/*
-		 * Maybe this page is still waiting for a cpu to drain it
-		 * from one of the lru lists?
-		 */
-		rc = schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
-		if (rc == 0 && PageLRU(page))
-			goto redo;
-	}
-	return rc;
-}
-
 /*
  * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
  */
@@ -865,40 +899,6 @@ static void shrink_cache(struct zone *zone, struct scan_control *sc)
 	pagevec_release(&pvec);
 }
 
-static inline void move_to_lru(struct page *page)
-{
-	list_del(&page->lru);
-	if (PageActive(page)) {
-		/*
-		 * lru_cache_add_active checks that
-		 * the PG_active bit is off.
-		 */
-		ClearPageActive(page);
-		lru_cache_add_active(page);
-	} else {
-		lru_cache_add(page);
-	}
-	put_page(page);
-}
-
-/*
- * Add isolated pages on the list back to the LRU
- *
- * returns the number of pages put back.
- */
-int putback_lru_pages(struct list_head *l)
-{
-	struct page *page;
-	struct page *page2;
-	int count = 0;
-
-	list_for_each_entry_safe(page, page2, l, lru) {
-		move_to_lru(page);
-		count++;
-	}
-	return count;
-}
-
 /*
  * This moves pages from the active list to the inactive list.
  *