writeback: account per-bdi accumulated written pages

Introduce the BDI_WRITTEN counter. It will be used for estimating the
bdi's write bandwidth.

Peter Zijlstra <a.p.zijlstra@chello.nl>:
Move BDI_WRITTEN accounting into __bdi_writeout_inc().
This will cover and fix fuse, which only calls bdi_writeout_inc().

CC: Michael Rubin <mrubin@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

2 files changed, 9 insertions, 2 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 7ba303be5e03..83f18a1d9d10 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -97,6 +97,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
                    "BdiDirtyThresh:   %8lu kB\n"
                    "DirtyThresh:      %8lu kB\n"
                    "BackgroundThresh: %8lu kB\n"
+                   "BdiWritten:       %8lu kB\n"
                    "b_dirty:          %8lu\n"
                    "b_io:             %8lu\n"
                    "b_more_io:        %8lu\n"
@@ -104,8 +105,13 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
                    "state:            %8lx\n",
                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
-                   K(bdi_thresh), K(dirty_thresh),
-                   K(background_thresh), nr_dirty, nr_io, nr_more_io,
+                   K(bdi_thresh),
+                   K(dirty_thresh),
+                   K(background_thresh),
+                   (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
+                   nr_dirty,
+                   nr_io,
+                   nr_more_io,
                    !list_empty(&bdi->bdi_list), bdi->state);
 #undef K
 
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 9d6ac2b6d942..8cd71376c63d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -219,6 +219,7 @@ int dirty_bytes_handler(struct ctl_table *table, int write,
  */
 static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
 {
+        __inc_bdi_stat(bdi, BDI_WRITTEN);
         __prop_inc_percpu_max(&vm_completions, &bdi->completions,
                               bdi->max_prop_frac);
 }