1 files changed, 94 insertions, 14 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 424239c075e2..aa340b097b6e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -43,6 +43,7 @@
 
 static DEFINE_PER_CPU(struct llist_head, blk_cpu_done);
 static DEFINE_PER_CPU(call_single_data_t, blk_cpu_csd);
+static DEFINE_MUTEX(blk_mq_cpuhp_lock);
 
 static void blk_mq_insert_request(struct request *rq, blk_insert_t flags);
 static void blk_mq_request_bypass_insert(struct request *rq,
@@ -3739,13 +3740,91 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
 	return 0;
 }
 
-static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
+static void __blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
 {
-	if (!(hctx->flags & BLK_MQ_F_STACKING))
+	lockdep_assert_held(&blk_mq_cpuhp_lock);
+
+	if (!(hctx->flags & BLK_MQ_F_STACKING) &&
+	    !hlist_unhashed(&hctx->cpuhp_online)) {
 		cpuhp_state_remove_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
 						    &hctx->cpuhp_online);
-	cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
-					    &hctx->cpuhp_dead);
+		INIT_HLIST_NODE(&hctx->cpuhp_online);
+	}
+
+	if (!hlist_unhashed(&hctx->cpuhp_dead)) {
+		cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
+						    &hctx->cpuhp_dead);
+		INIT_HLIST_NODE(&hctx->cpuhp_dead);
+	}
+}
+
+static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
+{
+	mutex_lock(&blk_mq_cpuhp_lock);
+	__blk_mq_remove_cpuhp(hctx);
+	mutex_unlock(&blk_mq_cpuhp_lock);
+}
+
+static void __blk_mq_add_cpuhp(struct blk_mq_hw_ctx *hctx)
+{
+	lockdep_assert_held(&blk_mq_cpuhp_lock);
+
+	if (!(hctx->flags & BLK_MQ_F_STACKING) &&
+	    hlist_unhashed(&hctx->cpuhp_online))
+		cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
+				&hctx->cpuhp_online);
+
+	if (hlist_unhashed(&hctx->cpuhp_dead))
+		cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD,
+				&hctx->cpuhp_dead);
+}
+
+static void __blk_mq_remove_cpuhp_list(struct list_head *head)
+{
+	struct blk_mq_hw_ctx *hctx;
+
+	lockdep_assert_held(&blk_mq_cpuhp_lock);
+
+	list_for_each_entry(hctx, head, hctx_list)
+		__blk_mq_remove_cpuhp(hctx);
+}
+
+/*
+ * Unregister cpuhp callbacks from exited hw queues
+ *
+ * Safe to call if this `request_queue` is live
+ */
+static void blk_mq_remove_hw_queues_cpuhp(struct request_queue *q)
+{
+	LIST_HEAD(hctx_list);
+
+	spin_lock(&q->unused_hctx_lock);
+	list_splice_init(&q->unused_hctx_list, &hctx_list);
+	spin_unlock(&q->unused_hctx_lock);
+
+	mutex_lock(&blk_mq_cpuhp_lock);
+	__blk_mq_remove_cpuhp_list(&hctx_list);
+	mutex_unlock(&blk_mq_cpuhp_lock);
+
+	spin_lock(&q->unused_hctx_lock);
+	list_splice(&hctx_list, &q->unused_hctx_list);
+	spin_unlock(&q->unused_hctx_lock);
+}
+
+/*
+ * Register cpuhp callbacks from all hw queues
+ *
+ * Safe to call if this `request_queue` is live
+ */
+static void blk_mq_add_hw_queues_cpuhp(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	mutex_lock(&blk_mq_cpuhp_lock);
+	queue_for_each_hw_ctx(q, hctx, i)
+		__blk_mq_add_cpuhp(hctx);
+	mutex_unlock(&blk_mq_cpuhp_lock);
 }
 
 /*
@@ -3796,8 +3875,6 @@ static void blk_mq_exit_hctx(struct request_queue *q,
 	if (set->ops->exit_hctx)
 		set->ops->exit_hctx(hctx, hctx_idx);
 
-	blk_mq_remove_cpuhp(hctx);
-
 	xa_erase(&q->hctx_table, hctx_idx);
 
 	spin_lock(&q->unused_hctx_lock);
@@ -3814,6 +3891,7 @@ static void blk_mq_exit_hw_queues(struct request_queue *q,
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (i == nr_queue)
 			break;
+		blk_mq_remove_cpuhp(hctx);
 		blk_mq_exit_hctx(q, set, hctx, i);
 	}
 }
@@ -3824,16 +3902,11 @@ static int blk_mq_init_hctx(struct request_queue *q,
 {
 	hctx->queue_num = hctx_idx;
 
-	if (!(hctx->flags & BLK_MQ_F_STACKING))
-		cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
-				&hctx->cpuhp_online);
-	cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
-
 	hctx->tags = set->tags[hctx_idx];
 
 	if (set->ops->init_hctx &&
 	    set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
-		goto unregister_cpu_notifier;
+		goto fail;
 
 	if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx,
 				hctx->numa_node))
@@ -3850,8 +3923,7 @@ static int blk_mq_init_hctx(struct request_queue *q,
  exit_hctx:
 	if (set->ops->exit_hctx)
 		set->ops->exit_hctx(hctx, hctx_idx);
- unregister_cpu_notifier:
-	blk_mq_remove_cpuhp(hctx);
+ fail:
 	return -1;
 }
 
@@ -3877,6 +3949,8 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
 	INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
 	spin_lock_init(&hctx->lock);
 	INIT_LIST_HEAD(&hctx->dispatch);
+	INIT_HLIST_NODE(&hctx->cpuhp_dead);
+	INIT_HLIST_NODE(&hctx->cpuhp_online);
 	hctx->queue = q;
 	hctx->flags = set->flags & ~BLK_MQ_F_TAG_QUEUE_SHARED;
 
@@ -4415,6 +4489,12 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 	xa_for_each_start(&q->hctx_table, j, hctx, j)
 		blk_mq_exit_hctx(q, set, hctx, j);
 	mutex_unlock(&q->sysfs_lock);
+
+	/* unregister cpuhp callbacks for exited hctxs */
+	blk_mq_remove_hw_queues_cpuhp(q);
+
+	/* register cpuhp for new initialized hctxs */
+	blk_mq_add_hw_queues_cpuhp(q);
 }
 
 int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,