mm: add free_hot_cold_page_list() helper

This patch adds helper free_hot_cold_page_list() to free list of 0-order
pages.  It frees pages directly from list without temporary page-vector.
It also calls trace_mm_pagevec_free() to simulate pagevec_free()
behaviour.

bloat-o-meter:

add/remove: 1/1 grow/shrink: 1/3 up/down: 267/-295 (-28)
function                                     old     new   delta
free_hot_cold_page_list                        -     264    +264
get_page_from_freelist                      2129    2132      +3
__pagevec_free                               243     239      -4
split_free_page                              380     373      -7
release_pages                                606     510     -96
free_page_list                               188       -    -188

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 753a2dc..3d571df 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -734,24 +734,6 @@
 	return PAGEREF_RECLAIM;
 }
 
-static noinline_for_stack void free_page_list(struct list_head *free_pages)
-{
-	struct pagevec freed_pvec;
-	struct page *page, *tmp;
-
-	pagevec_init(&freed_pvec, 1);
-
-	list_for_each_entry_safe(page, tmp, free_pages, lru) {
-		list_del(&page->lru);
-		if (!pagevec_add(&freed_pvec, page)) {
-			__pagevec_free(&freed_pvec);
-			pagevec_reinit(&freed_pvec);
-		}
-	}
-
-	pagevec_free(&freed_pvec);
-}
-
 /*
  * shrink_page_list() returns the number of reclaimed pages
  */
@@ -1015,7 +997,7 @@
 	if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
 		zone_set_flag(zone, ZONE_CONGESTED);
 
-	free_page_list(&free_pages);
+	free_hot_cold_page_list(&free_pages, 1);
 
 	list_splice(&ret_pages, page_list);
 	count_vm_events(PGACTIVATE, pgactivate);