[PATCH] count bounce buffer pages in vmstat

This is a patch for counting the number of pages for bounce buffers.  It's
shown in /proc/vmstat.

Currently, the number of bounce pages are not counted anywhere.  So, if
there are many bounce pages, it seems that there are leaked pages.  And
it's difficult for a user to imagine the usage of bounce pages.  So, it's
meaningful to show # of bouce pages.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/page-flags.h

@@ -131,6 +131,7 @@ struct page_state {
 	unsigned long allocstall;	/* direct reclaim calls */
 
 	unsigned long pgrotated;	/* pages rotated to tail of the LRU */
+	unsigned long nr_bounce;	/* pages for bounce buffers */
 };
 
 extern void get_page_state(struct page_state *ret);