linux-kernel - [PATCH v3 2/3] block, bfq: avoid moving bfqq to it's parent bfqg

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Message-ID: <20220129015924.3958918-3-yukuai3@huawei.com>
Date:   Sat, 29 Jan 2022 09:59:23 +0800
From:   Yu Kuai <yukuai3@...wei.com>
To:     <paolo.valente@...aro.org>, <jack@...e.cz>, <axboe@...nel.dk>
CC:     <linux-block@...r.kernel.org>, <cgroups@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <yukuai3@...wei.com>,
        <yi.zhang@...wei.com>
Subject: [PATCH v3 2/3] block, bfq: avoid moving bfqq to it's parent bfqg

Moving bfqq to it's parent bfqg is pointless.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/bfq-cgroup.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 24a5c5329bcd..9783c1156159 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -645,6 +645,14 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 		   struct bfq_group *bfqg)
 {
 	struct bfq_entity *entity = &bfqq->entity;
+	struct bfq_group *old_parent = bfqq_group(bfqq);
+
+	/*
+	 * No point to move bfqq to the same group, which can happen when
+	 * root group is offlined
+	 */
+	if (old_parent == bfqg)
+		return;
 
 	/*
 	 * Get extra reference to prevent bfqq from being freed in
@@ -666,7 +674,7 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 		bfq_deactivate_bfqq(bfqd, bfqq, false, false);
 	else if (entity->on_st_or_in_serv)
 		bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
-	bfqg_and_blkg_put(bfqq_group(bfqq));
+	bfqg_and_blkg_put(old_parent);
 
 	if (entity->parent &&
 	    entity->parent->last_bfqq_created == bfqq)
-- 
2.31.1