bcache: set writeback_rate_update_seconds in range [1, 60] seconds

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.

Changelog:
v2: fix a rebase typo in v4, which is pointed out by Michael Lyle.
v1: initial version.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index c524305..4a6a697 100644 (file)
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -218,7 +218,9 @@ STORE(__cached_dev)
        sysfs_strtoul_clamp(writeback_rate,
                            dc->writeback_rate.rate, 1, INT_MAX);
 
-       d_strtoul_nonzero(writeback_rate_update_seconds);
+       sysfs_strtoul_clamp(writeback_rate_update_seconds,
+                           dc->writeback_rate_update_seconds,
+                           1, WRITEBACK_RATE_UPDATE_SECS_MAX);
        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 58218f7..f1d2fc1 100644 (file)
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -655,7 +655,7 @@ 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 66f1c52..587b255 100644 (file)
--- 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