linux-kernel - [PATCH 4.14 161/190] blk-mq: move _blk_mq_update_nr_hw_queues synchronize

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Date:   Fri, 19 Jun 2020 16:33:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Giuliano Procida <gprocida@...gle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 161/190] blk-mq: move _blk_mq_update_nr_hw_queues synchronize_rcu call

From: Giuliano Procida <gprocida@...gle.com>

This fixes the
4.14 backport commit 574eb136ec7f315c3ef2ca68fa9b3e16c56baa24
which was
upstream commit f5bbbbe4d63577026f908a809f22f5fd5a90ea1f.

The upstream commit added a call to synchronize_rcu to
_blk_mq_update_nr_hw_queues, just after freezing queues.

In the backport this landed just after unfreezeing queues.

This commit moves the call to its intended place.

Fixes: 574eb136ec7f ("blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter")
Signed-off-by: Giuliano Procida <gprocida@...gle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 block/blk-mq.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9d53f476c517..cf56bdad2e06 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2738,6 +2738,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 
 	list_for_each_entry(q, &set->tag_list, tag_set_list)
 		blk_mq_freeze_queue(q);
+	/*
+	 * Sync with blk_mq_queue_tag_busy_iter.
+	 */
+	synchronize_rcu();
 
 	set->nr_hw_queues = nr_hw_queues;
 	blk_mq_update_queue_map(set);
@@ -2748,10 +2752,6 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 
 	list_for_each_entry(q, &set->tag_list, tag_set_list)
 		blk_mq_unfreeze_queue(q);
-	/*
-	 * Sync with blk_mq_queue_tag_busy_iter.
-	 */
-	synchronize_rcu();
 }
 
 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
-- 
2.25.1