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/mm/page-writeback.c b/mm/page-writeback.c
index 94159819a651..4dd91f7fd39f 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1121,6 +1121,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
 {
         if (mapping_cap_account_dirty(mapping)) {
                 __inc_zone_page_state(page, NR_FILE_DIRTY);
+                __inc_zone_page_state(page, NR_DIRTIED);
                 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
                 task_dirty_inc(current);
                 task_io_account_write(PAGE_CACHE_SIZE);
@@ -1136,6 +1137,7 @@ EXPORT_SYMBOL(account_page_dirtied);
 void account_page_writeback(struct page *page)
 {
         inc_zone_page_state(page, NR_WRITEBACK);
+        inc_zone_page_state(page, NR_WRITTEN);
 }
 EXPORT_SYMBOL(account_page_writeback);