Commit c9589f03 authored Aug 18, 2015 by Tejun Heo Committed by Jens Axboe Aug 18, 2015

blk-throttle: improve queue bypass handling



If a queue is bypassing, all blkcg policies should become noops but
blk-throttle wasn't.  It only became noop if the queue was dying.
While this wouldn't lead to an oops as falling back to the root blkg
is safe in this case, this can be a bit surprising - a bypassing queue
could still be applying throttle limits.

Fix it by removing blk_queue_dying() test in throtl_lookup_create_tg()
and testing blk_queue_bypass() in blk_throtl_bio() and bypassing
before doing anything else.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent 85b6bc9d

block/blk-throttle.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -475,7 +475,7 @@ static struct throtl_grp throtl_lookup_create_tg(struct throtl_data td,
		/* if %NULL and @q is alive, fall back to root_tg */
		if (!IS_ERR(blkg))
		tg = blkg_to_tg(blkg);
		else if (!blk_queue_dying(q))
		else
		tg = td_root_tg(td);
		}

		@@ -1438,10 +1438,11 @@ bool blk_throtl_bio(struct request_queue q, struct bio bio)
		* IO group
		*/
		spin_lock_irq(q->queue_lock);
		tg = throtl_lookup_create_tg(td, blkcg);
		if (unlikely(!tg))

		if (unlikely(blk_queue_bypass(q)))
		goto out_unlock;

		tg = throtl_lookup_create_tg(td, blkcg);
		sq = &tg->service_queue;

		while (true) {