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Commit c125311d authored by Jens Axboe's avatar Jens Axboe
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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: c1c80384 ("block: remove external dependency on wbt_flags")
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c45e6a03

block/blk-sysfs.c

+18 −1
Original line number Diff line number Diff line
@@ -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;

}

block/blk-wbt.c

+3 −0
Original line number Diff line number Diff line
@@ -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)) {