linux-kernel - [PATCH 5.8 160/186] blk-stat: make q->stats->lock irqsafe

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Message-Id: <20200908152249.419945317@linuxfoundation.org>
Date:   Tue,  8 Sep 2020 17:25:02 +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, Tejun Heo <tj@...nel.org>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.8 160/186] blk-stat: make q->stats->lock irqsafe

From: Tejun Heo <tj@...nel.org>

commit e11d80a849e010f78243bb6f6af7dccef3a71a90 upstream.

blk-iocost calls blk_stat_enable_accounting() while holding an irqsafe lock
which triggers a lockdep splat because q->stats->lock isn't irqsafe. Let's
make it irqsafe.

Signed-off-by: Tejun Heo <tj@...nel.org>
Fixes: cd006509b0a9 ("blk-iocost: account for IO size when testing latencies")
Cc: stable@...r.kernel.org # v5.8+
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/blk-stat.c |   17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -137,6 +137,7 @@ void blk_stat_add_callback(struct reques
 			   struct blk_stat_callback *cb)
 {
 	unsigned int bucket;
+	unsigned long flags;
 	int cpu;
 
 	for_each_possible_cpu(cpu) {
@@ -147,20 +148,22 @@ void blk_stat_add_callback(struct reques
 			blk_rq_stat_init(&cpu_stat[bucket]);
 	}
 
-	spin_lock(&q->stats->lock);
+	spin_lock_irqsave(&q->stats->lock, flags);
 	list_add_tail_rcu(&cb->list, &q->stats->callbacks);
 	blk_queue_flag_set(QUEUE_FLAG_STATS, q);
-	spin_unlock(&q->stats->lock);
+	spin_unlock_irqrestore(&q->stats->lock, flags);
 }
 
 void blk_stat_remove_callback(struct request_queue *q,
 			      struct blk_stat_callback *cb)
 {
-	spin_lock(&q->stats->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&q->stats->lock, flags);
 	list_del_rcu(&cb->list);
 	if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
 		blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
-	spin_unlock(&q->stats->lock);
+	spin_unlock_irqrestore(&q->stats->lock, flags);
 
 	del_timer_sync(&cb->timer);
 }
@@ -183,10 +186,12 @@ void blk_stat_free_callback(struct blk_s
 
 void blk_stat_enable_accounting(struct request_queue *q)
 {
-	spin_lock(&q->stats->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&q->stats->lock, flags);
 	q->stats->enable_accounting = true;
 	blk_queue_flag_set(QUEUE_FLAG_STATS, q);
-	spin_unlock(&q->stats->lock);
+	spin_unlock_irqrestore(&q->stats->lock, flags);
 }
 EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);