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/include/linux/gfp.h b/include/linux/gfp.h
index 3a76faf..6562958 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -358,6 +358,7 @@
 extern void __free_pages(struct page *page, unsigned int order);
 extern void free_pages(unsigned long addr, unsigned int order);
 extern void free_hot_cold_page(struct page *page, int cold);
+extern void free_hot_cold_page_list(struct list_head *list, int cold);
 
 #define __free_page(page) __free_pages((page), 0)
 #define free_page(addr) free_pages((addr), 0)