Re: [PATCH v5 01/10] bcache: set writeback_rate_update_seconds in range [1, 60] seconds

Michael Lyle
2018-02-07T17:31:42Z

LGTM-- in my staging branch.

Reviewed-by: Michael Lyle <mlyle@lyle.org>

On 02/05/2018 08:20 PM, Coly Li wrote:
> 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>
> Cc: Michael Lyle <mlyle@lyle.org>
> ---
> drivers/md/bcache/sysfs.c | 4 +++-
> drivers/md/bcache/writeback.c | 2 +-
> drivers/md/bcache/writeback.h | 3 +++
> 3 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
> index c524305cc9a7..4a6a697e1680 100644
> --- 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 58218f7e77c3..f1d2fc15abcc 100644
> --- 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 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
>