[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);

mm/highmem.c

@@ -325,6 +325,7 @@ static void bounce_end_io(struct bio *bio, mempool_t *pool, int err)
 			continue;
 
 		mempool_free(bvec->bv_page, pool);	
+		dec_page_state(nr_bounce);
 	}
 
 	bio_endio(bio_orig, bio_orig->bi_size, err);
@@ -405,6 +406,7 @@ static void __blk_queue_bounce(request_queue_t *q, struct bio **bio_orig,
 		to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 		to->bv_len = from->bv_len;
 		to->bv_offset = from->bv_offset;
+		inc_page_state(nr_bounce);
 
 		if (rw == WRITE) {
 			char *vto, *vfrom;

mm/page_alloc.c

@@ -1897,6 +1897,7 @@ static char *vmstat_text[] = {
 	"allocstall",
 
 	"pgrotated",
+	"nr_bounce",
 };
 
 static void *vmstat_start(struct seq_file *m, loff_t *pos)