blk-wbt: don't maintain inflight counts if disabled

A previous commit removed the ability to have per-rq flags. We used
those flags to maintain inflight counts. Since we don't have those
anymore, we have to always maintain inflight counts, even if wbt is
disabled. This is clearly suboptimal.

Add a queue quiesce around changing the wbt latency settings from sysfs
to work around this. With that, we can reliably put the enabled check in
our bio_to_wbt_flags(), since we know the WBT_TRACKED flag will be
consistent for the lifetime of the request.

Fixes: c1c80384c8 ("block: remove external dependency on wbt_flags")
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-08-23 09:34:46 -06:00
parent c45e6a037a
commit c125311d96
2 changed files with 21 additions and 1 deletions

View File

@ -453,9 +453,26 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
else if (val >= 0)
val *= 1000ULL;
wbt_set_min_lat(q, val);
/*
* Ensure that the queue is idled, in case the latency update
* ends up either enabling or disabling wbt completely. We can't
* have IO inflight if that happens.
*/
if (q->mq_ops) {
blk_mq_freeze_queue(q);
blk_mq_quiesce_queue(q);
} else
blk_queue_bypass_start(q);
wbt_set_min_lat(q, val);
wbt_update_limits(q);
if (q->mq_ops) {
blk_mq_unquiesce_queue(q);
blk_mq_unfreeze_queue(q);
} else
blk_queue_bypass_end(q);
return count;
}

View File

@ -540,6 +540,9 @@ static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio)
{
enum wbt_flags flags = 0;
if (!rwb_enabled(rwb))
return 0;
if (bio_op(bio) == REQ_OP_READ) {
flags = WBT_READ;
} else if (wbt_should_throttle(rwb, bio)) {