[PATCH v4 01/13] bcache: set writeback_rate_update_seconds in range [1, 60] seconds

Coly Li
2018-01-28T02:54:25Z

dc->writeback_rate_update_seconds can be set via sysfs and its value can
be set to [1, ULONG_MAX]. It does not make sense to set such a large
value, 60 seconds is long enough value considering the default 5 seconds
works well for long time.

Because dc->writeback_rate_update is a special delayed work, it re-arms
itself inside the delayed work routine update_writeback_rate(). When
stopping it by cancel_delayed_work_sync(), there should be a timeout to
wait and make sure the re-armed delayed work is stopped too. A small max
value of dc->writeback_rate_update_seconds is also helpful to decide a
reasonable small timeout.

This patch limits sysfs interface to set dc->writeback_rate_update_seconds
in range of [1, 60] seconds, and replaces the hand-coded number by macros.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
---
drivers/md/bcache/sysfs.c | 3 +++
drivers/md/bcache/writeback.c | 2 +-
drivers/md/bcache/writeback.h | 3 +++
3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index b4184092c727..a74a752c9e0f 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -215,6 +215,9 @@ STORE(__cached_dev)
sysfs_strtoul_clamp(writeback_rate,
dc->writeback_rate.rate, 1, INT_MAX);

+ sysfs_strtoul_clamp(writeback_rate_update_seconds,
+ dc->writeback_rate_update_seconds,
+ 1, WRITEBACK_RATE_UPDATE_SECS_MAX);
d_strtoul_nonzero(writeback_rate_update_seconds);
d_strtoul(writeback_rate_i_term_inverse);
d_strtoul_nonzero(writeback_rate_p_term_inverse);
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 51306a19ab03..0ade883b6316 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -652,7 +652,7 @@ void bch_cached_dev_writeback_init(struct cached_dev *dc)
dc->writeback_rate.rate = 1024;
dc->writeback_rate_minimum = 8;

- dc->writeback_rate_update_seconds = 5;
+ dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;
dc->writeback_rate_p_term_inverse = 40;
dc->writeback_rate_i_term_inverse = 10000;

diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h
index 66f1c527fa24..587b25599856 100644
--- a/drivers/md/bcache/writeback.h
+++ b/drivers/md/bcache/writeback.h
@@ -8,6 +8,9 @@
#define MAX_WRITEBACKS_IN_PASS 5
#define MAX_WRITESIZE_IN_PASS 5000 /* *512b */

+#define WRITEBACK_RATE_UPDATE_SECS_MAX 60
+#define WRITEBACK_RATE_UPDATE_SECS_DEFAULT 5
+
/*
* 14 (16384ths) is chosen here as something that each backing device
* should be a reasonable fraction of the share, and not to blow up
--
2.15.1