From cc38ca7ed54a1df04ae9f23614b348ebfc918029 Mon Sep 17 00:00:00 2001
From: Coly Li <colyli@suse.de>
Date: Thu, 13 Dec 2018 22:53:56 +0800
Subject: [PATCH] bcache: set writeback_percent in a flexible range
Git-commit: cc38ca7ed54a1df04ae9f23614b348ebfc918029
Patch-mainline: v5.0-rc1
References: bsc#1130972

Because CUTOFF_WRITEBACK is defined as 40, so before the changes of
dynamic cutoff writeback values, writeback_percent is limited to [0,
CUTOFF_WRITEBACK]. Any value larger than CUTOFF_WRITEBACK will be fixed
up to 40.

Now cutof writeback limit is a dynamic value bch_cutoff_writeback, so
the range of writeback_percent can be a more flexible range as [0,
bch_cutoff_writeback]. The flexibility is, it can be expended to a
larger or smaller range than [0, 40], depends on how value
bch_cutoff_writeback is specified.

The default value is still strongly recommended to most of users for
most of workloads. But for people who want to do research on bcache
writeback perforamnce tuning, they may have chance to specify more
flexible writeback_percent in range [0, 70].

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

---
 drivers/md/bcache/sysfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 482b128b3e9d..557a8a3270a1 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -267,7 +267,8 @@ STORE(__cached_dev)
 	d_strtoul(writeback_running);
 	d_strtoul(writeback_delay);
 
-	sysfs_strtoul_clamp(writeback_percent, dc->writeback_percent, 0, 40);
+	sysfs_strtoul_clamp(writeback_percent, dc->writeback_percent,
+			    0, bch_cutoff_writeback);
 
 	if (attr == &sysfs_writeback_rate) {
 		ssize_t ret;
-- 
2.16.4