On Thu 22-09-22 19:35:54, Yu Kuai wrote:
> Currently, if wbt is initialized and then disabled by
> wbt_disable_default(), sysfs will still show valid wbt_lat_usec, which
> will confuse users that wbt is still enabled.
>
> This patch shows wbt_lat_usec as zero and forbid to set it while wbt
> is disabled.
So I agree we should show 0 in wbt_lat_usec if wbt is disabled by
wbt_disable_default(). But why do you forbid setting of wbt_lat_usec?
IMHO if wbt_lat_usec is set, admin wants to turn on wbt so we should just
update rwb->enable_state to WBT_STATE_ON_MANUAL.
Honza
>
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> Reported-and-tested-by: Holger Hoffstätte <holger@xxxxxxxxxxxxxxxxxxxxxx>
> ---
> block/blk-sysfs.c | 9 ++++++++-
> block/blk-wbt.c | 7 +++++++
> block/blk-wbt.h | 5 +++++
> 3 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index e1f009aba6fd..1955bb6a284d 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -467,10 +467,14 @@ static ssize_t queue_io_timeout_store(struct request_queue *q, const char *page,
>
> static ssize_t queue_wb_lat_show(struct request_queue *q, char *page)
> {
> + u64 lat;
> +
> if (!wbt_rq_qos(q))
> return -EINVAL;
>
> - return sprintf(page, "%llu\n", div_u64(wbt_get_min_lat(q), 1000));
> + lat = wbt_disabled(q) ? 0 : div_u64(wbt_get_min_lat(q), 1000);
> +
> + return sprintf(page, "%llu\n", lat);
> }
>
> static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
> @@ -493,6 +497,9 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
> return ret;
> }
>
> + if (wbt_disabled(q))
> + return -EINVAL;
> +
> if (val == -1)
> val = wbt_default_latency_nsec(q);
> else if (val >= 0)
> diff --git a/block/blk-wbt.c b/block/blk-wbt.c
> index a9982000b667..68851c2c02d2 100644
> --- a/block/blk-wbt.c
> +++ b/block/blk-wbt.c
> @@ -422,6 +422,13 @@ static void wbt_update_limits(struct rq_wb *rwb)
> rwb_wake_all(rwb);
> }
>
> +bool wbt_disabled(struct request_queue *q)
> +{
> + struct rq_qos *rqos = wbt_rq_qos(q);
> +
> + return !rqos || RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT;
> +}
> +
> u64 wbt_get_min_lat(struct request_queue *q)
> {
> struct rq_qos *rqos = wbt_rq_qos(q);
> diff --git a/block/blk-wbt.h b/block/blk-wbt.h
> index 7e44eccc676d..e42465ddcbb6 100644
> --- a/block/blk-wbt.h
> +++ b/block/blk-wbt.h
> @@ -94,6 +94,7 @@ void wbt_enable_default(struct request_queue *);
>
> u64 wbt_get_min_lat(struct request_queue *q);
> void wbt_set_min_lat(struct request_queue *q, u64 val);
> +bool wbt_disabled(struct request_queue *);
>
> void wbt_set_write_cache(struct request_queue *, bool);
>
> @@ -125,6 +126,10 @@ static inline u64 wbt_default_latency_nsec(struct request_queue *q)
> {
> return 0;
> }
> +static inline bool wbt_disabled(struct request_queue *q)
> +{
> + return true;
> +}
>
> #endif /* CONFIG_BLK_WBT */
>
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
