block: make queue stat accounting a reference

kyber turns on IO statistics when it is loaded on a queue, which means
that even if kyber is then later unloaded, we're still stuck with stats
enabled on the queue.

Change the account enabled from a bool to an int, and pair the enable call
with the equivalent disable call. This ensures that stats gets turned off
again appropriately.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-stat.c b/block/blk-stat.c
index efb2a80..2ea01b5 100644 (file)
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -15,7 +15,7 @@
 struct blk_queue_stats {
        struct list_head callbacks;
        spinlock_t lock;
-       bool enable_accounting;
+       int accounting;
 };
 
 void blk_rq_stat_init(struct blk_rq_stat *stat)
@@ -161,7 +161,7 @@ void blk_stat_remove_callback(struct request_queue *q,
 
        spin_lock_irqsave(&q->stats->lock, flags);
        list_del_rcu(&cb->list);
-       if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
+       if (list_empty(&q->stats->callbacks) && !q->stats->accounting)
                blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
        spin_unlock_irqrestore(&q->stats->lock, flags);
 
@@ -184,13 +184,24 @@ void blk_stat_free_callback(struct blk_stat_callback *cb)
                call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
 }
 
+void blk_stat_disable_accounting(struct request_queue *q)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&q->stats->lock, flags);
+       if (!--q->stats->accounting)
+               blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
+       spin_unlock_irqrestore(&q->stats->lock, flags);
+}
+EXPORT_SYMBOL_GPL(blk_stat_disable_accounting);
+
 void blk_stat_enable_accounting(struct request_queue *q)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&q->stats->lock, flags);
-       q->stats->enable_accounting = true;
-       blk_queue_flag_set(QUEUE_FLAG_STATS, q);
+       if (!q->stats->accounting++)
+               blk_queue_flag_set(QUEUE_FLAG_STATS, q);
        spin_unlock_irqrestore(&q->stats->lock, flags);
 }
 EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);
@@ -205,7 +216,7 @@ struct blk_queue_stats *blk_alloc_queue_stats(void)
 
        INIT_LIST_HEAD(&stats->callbacks);
        spin_lock_init(&stats->lock);
-       stats->enable_accounting = false;
+       stats->accounting = 0;
 
        return stats;
 }

diff --git a/block/blk-stat.h b/block/blk-stat.h
index 58f029a..17e1eb4 100644 (file)
--- a/block/blk-stat.h
+++ b/block/blk-stat.h
@@ -70,6 +70,7 @@ void blk_stat_add(struct request *rq, u64 now);
 
 /* record time/size info in request but not add a callback */
 void blk_stat_enable_accounting(struct request_queue *q);
+void blk_stat_disable_accounting(struct request_queue *q);
 
 /**
  * blk_stat_alloc_callback() - Allocate a block statistics callback.

diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index fdd74a4..70ff2a5 100644 (file)
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -433,6 +433,7 @@ static void kyber_exit_sched(struct elevator_queue *e)
        int i;
 
        del_timer_sync(&kqd->timer);
+       blk_stat_disable_accounting(kqd->q);
 
        for (i = 0; i < KYBER_NUM_DOMAINS; i++)
                sbitmap_queue_free(&kqd->domain_tokens[i]);