From a8500fc816b19795756d27c762daa5e19f5e1b6f Mon Sep 17 00:00:00 2001
From: Michael Lyle <mlyle@lyle.org>
Date: Fri, 13 Oct 2017 16:35:39 -0700
Subject: [PATCH] bcache: rearrange writeback main thread ratelimit
Git-commit: a8500fc816b19795756d27c762daa5e19f5e1b6f
Patch-mainline: v4.15-rc1
References: bsc#1076110

The time spent searching for things to write back "counts" for the
actual rate achieved, so don't flush the accumulated rate with each
chunk.

This will maintain better fidelity to user-commanded rates, but it
may slightly increase the burstiness of writeback.  The writeback
lock needs improvement to help mitigate this.

Signed-off-by: Michael Lyle <mlyle@lyle.org>
Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/bcache/writeback.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 897d28050656..9b770b13bdf6 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -440,6 +440,8 @@ static int bch_writeback_thread(void *arg)
 	struct cached_dev *dc = arg;
 	bool searched_full_index;
 
+	bch_ratelimit_reset(&dc->writeback_rate);
+
 	while (!kthread_should_stop()) {
 		down_write(&dc->writeback_lock);
 		if (!atomic_read(&dc->has_dirty) ||
@@ -467,7 +469,6 @@ static int bch_writeback_thread(void *arg)
 
 		up_write(&dc->writeback_lock);
 
-		bch_ratelimit_reset(&dc->writeback_rate);
 		read_dirty(dc);
 
 		if (searched_full_index) {
@@ -477,6 +478,8 @@ static int bch_writeback_thread(void *arg)
 			       !kthread_should_stop() &&
 			       !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
 				delay = schedule_timeout_interruptible(delay);
+
+			bch_ratelimit_reset(&dc->writeback_rate);
 		}
 	}
 
-- 
2.15.1