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 <[email protected]> Cc: Vivek Goyal <[email protected]> Cc: Arianna Avanzini <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
josf · Aug 18, 2015 · c9589f0 · c9589f0
1 parent 85b6bc9
commit c9589f0
Showing 1 changed file with 4 additions and 3 deletions.
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
@@ -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) {