From: Paolo Valente <paolo.valente@linaro.org>
Date: Thu, 16 Aug 2018 18:51:16 +0200
Subject: [PATCH] block, bfq: always update the budget of an entity when needed
Git-commit: e02a0aa26bf61b6e481a3d7453a150e692b0df80
Patch-mainline: v4.19-rc1
References: bsc#1104967,FATE#325924

When the next child entity to serve changes for a given parent entity,
the budget of that parent entity must be updated accordingly.
Unfortunately, this update is not performed, by mistake, for the
entities that happen to switch from having no child entity to serve,
to having one child entity to serve.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/bfq-wf2q.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index dbc07b456059..d558fd26740c 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -130,10 +130,14 @@ static bool bfq_update_next_in_service(struct bfq_sched_data *sd,
 	if (!change_without_lookup) /* lookup needed */
 		next_in_service = bfq_lookup_next_entity(sd, expiration);
 
-	if (next_in_service)
-		parent_sched_may_change = !sd->next_in_service ||
+	if (next_in_service) {
+		bool new_budget_triggers_change =
 			bfq_update_parent_budget(next_in_service);
 
+		parent_sched_may_change = !sd->next_in_service ||
+			new_budget_triggers_change;
+	}
+
 	sd->next_in_service = next_in_service;
 
 	if (!next_in_service)
-- 
2.16.4