From 27cdc2ee79dd132d494ddae0d4a49077760f8dbb Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 9 Apr 2020 16:17:51 +0200
Subject: [PATCH] bfq: Fix check detecting whether waker queue should be
 selected
Patch-mainline: Not yet, submitted 09/04/2020
References: bsc#1168838

The check in bfq_select_queue() checking whether a waker queue should be
selected has a bug and is checking bfqq->next_rq instead of
bfqq->waker_bfqq->next_rq to verify whether the waker queue has a
request to dispatch. This often results in the condition being false
(most notably when the current queue is idling waiting for next request)
and thus the waker queue logic is ineffective. Fix the condition.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 block/bfq-iosched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 3ed484054d48..06c420d98bd2 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4585,7 +4585,7 @@ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
 			bfqq = bfqq->bic->bfqq[0];
 		else if (bfq_bfqq_has_waker(bfqq) &&
 			   bfq_bfqq_busy(bfqq->waker_bfqq) &&
-			   bfqq->next_rq &&
+			   bfqq->waker_bfqq->next_rq &&
 			   bfq_serv_to_charge(bfqq->waker_bfqq->next_rq,
 					      bfqq->waker_bfqq) <=
 			   bfq_bfqq_budget_left(bfqq->waker_bfqq)
-- 
2.16.4