mm, highmem: remove page_address_pool list

We can find free page_address_map instance without the page_address_pool.
So remove it.
Signed-off-by: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/highmem.c

@@ -324,10 +324,7 @@ struct page_address_map {
 	struct list_head list;
 };
 
-/*
- * page_address_map freelist, allocated from page_address_maps.
- */
-static struct list_head page_address_pool;	/* freelist */
+static struct page_address_map page_address_maps[LAST_PKMAP];
 
 /*
  * Hash table bucket
@@ -392,12 +389,7 @@ void set_page_address(struct page *page, void *virtual)
 
 	pas = page_slot(page);
 	if (virtual) {		/* Add */
-		BUG_ON(list_empty(&page_address_pool));
-
-		pam = list_entry(page_address_pool.next,
-				struct page_address_map, list);
-		list_del(&pam->list);
-
+		pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
 		pam->page = page;
 		pam->virtual = virtual;
 
@@ -410,7 +402,6 @@ void set_page_address(struct page *page, void *virtual)
 			if (pam->page == page) {
 				list_del(&pam->list);
 				spin_unlock_irqrestore(&pas->lock, flags);
-				list_add_tail(&pam->list, &page_address_pool);
 				goto done;
 			}
 		}
@@ -420,15 +411,10 @@ void set_page_address(struct page *page, void *virtual)
 	return;
 }
 
-static struct page_address_map page_address_maps[LAST_PKMAP];
-
 void __init page_address_init(void)
 {
 	int i;
 
-	INIT_LIST_HEAD(&page_address_pool);
-	for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
-		list_add(&page_address_maps[i].list, &page_address_pool);
 	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 		INIT_LIST_HEAD(&page_address_htable[i].lh);
 		spin_lock_init(&page_address_htable[i].lock);