blk-wbt: don't show valid wbt_lat_usec in sysfs while wbt is disabled

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 if it's disabled.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reported-and-tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221019121518.3865235-5-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index e71b3b4..7b98c70 100644 (file)
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -470,6 +470,9 @@ static ssize_t queue_wb_lat_show(struct request_queue *q, char *page)
        if (!wbt_rq_qos(q))
                return -EINVAL;
 
+       if (wbt_disabled(q))
+               return sprintf(page, "0\n");
+
        return sprintf(page, "%llu\n", div_u64(wbt_get_min_lat(q), 1000));
 }
 

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 4680691..07ed0b0 100644 (file)
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -422,6 +422,14 @@ 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 ||
+              RQWB(rqos)->enable_state == WBT_STATE_OFF_MANUAL;
+}
+
 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 7fe9863..e3ea6e7 100644 (file)
--- a/block/blk-wbt.h
+++ b/block/blk-wbt.h
@@ -96,6 +96,7 @@ 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);
 
@@ -127,6 +128,10 @@ 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 */