blk-stat: make q->stats->lock irqsafe

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@kernel.org>
Fixes: cd006509b0a9 ("blk-iocost: account for IO size when testing latencies")
Cc: stable@vger.kernel.org # v5.8+
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-stat.c b/block/blk-stat.c
index 7da302f..ae3dd1f 100644 (file)
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -137,6 +137,7 @@ void blk_stat_add_callback(struct request_queue *q,
                           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 request_queue *q,
                        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_stat_callback *cb)
 
 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);