writeback: add nr_dirtied and nr_written to /proc/vmstat

To help developers and applications gain visibility into writeback
behaviour adding two entries to vm_stat_items and /proc/vmstat.  This will
allow us to track the "written" and "dirtied" counts.

   # grep nr_dirtied /proc/vmstat
   nr_dirtied 3747
   # grep nr_written /proc/vmstat
   nr_written 3618

Signed-off-by: Michael Rubin <mrubin@google.com>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3984c4eb41fd..c3c17fb675ee 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -104,6 +104,8 @@ enum zone_stat_item {
         NR_ISOLATED_ANON,       /* Temporary isolated pages from anon lru */
         NR_ISOLATED_FILE,       /* Temporary isolated pages from file lru */
         NR_SHMEM,               /* shmem pages (included tmpfs/GEM pages) */
+        NR_DIRTIED,             /* page dirtyings since bootup */
+        NR_WRITTEN,             /* page writings since bootup */
 #ifdef CONFIG_NUMA
         NUMA_HIT,               /* allocated in intended node */
         NUMA_MISS,              /* allocated in non intended node */