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block: Make WBT latency writes honor enable state

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queue/wbt_lat_usec controls both the stored WBT latency target and the
effective WBT enable state.

The old no-op check skipped updates whenever the converted latency
matched the stored min_lat_nsec. That check ignored whether the current
WBT state already matched the state requested by the write. For a queue
disabled by default, attempting to enable WBT by writing the default
value through sysfs could return success while the enable state was left
unchanged.

Treat a write as a no-op only when both the stored latency and the
effective WBT enabled state already match the converted value.

Signed-off-by: Guzebing <guzebing1612@gmail.com>
Link: https://patch.msgid.link/20260621014030.1625306-1-guzebing1612@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Guzebing
2026-06-21 09:40:30 +08:00
committed by Jens Axboe
parent 3dd63dba8f
commit 1e56f30a73
1 changed files with 20 additions and 1 deletions
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21
block/blk-wbt.c
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@@ -813,6 +813,21 @@ static void wbt_queue_depth_changed(struct rq_qos *rqos)
wbt_update_limits(RQWB(rqos));
}
static bool wbt_set_lat_changed(struct request_queue *q, u64 val)
{
struct rq_qos *rqos = wbt_rq_qos(q);
struct rq_wb *rwb;
if (!rqos)
return true;
rwb = RQWB(rqos);
if (rwb->min_lat_nsec != val)
return true;
return rwb_enabled(rwb) != !!val;
}
static void wbt_exit(struct rq_qos *rqos)
{
struct rq_wb *rwb = RQWB(rqos);
@@ -1005,8 +1020,12 @@ int wbt_set_lat(struct gendisk *disk, s64 val)
else if (val >= 0)
val *= 1000ULL;
if (wbt_get_min_lat(q) == val)
mutex_lock(&disk->rqos_state_mutex);
if (!wbt_set_lat_changed(q, val)) {
mutex_unlock(&disk->rqos_state_mutex);
goto out;
}
mutex_unlock(&disk->rqos_state_mutex);
blk_mq_quiesce_queue(q);