blk-mq: handle failure path for initializing hctx

Failure of initializing one hctx isn't handled, so this patch
introduces blk_mq_init_hctx() and its pair to handle it explicitly.
Also this patch makes code cleaner.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -1509,6 +1509,20 @@ static int blk_mq_hctx_notify(void *data, unsigned long action,
 	return NOTIFY_OK;
 }
 
+static void blk_mq_exit_hctx(struct request_queue *q,
+		struct blk_mq_tag_set *set,
+		struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
+{
+	blk_mq_tag_idle(hctx);
+
+	if (set->ops->exit_hctx)
+		set->ops->exit_hctx(hctx, hctx_idx);
+
+	blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
+	kfree(hctx->ctxs);
+	blk_mq_free_bitmap(&hctx->ctx_map);
+}
+
 static void blk_mq_exit_hw_queues(struct request_queue *q,
 		struct blk_mq_tag_set *set, int nr_queue)
 {
@@ -1518,17 +1532,8 @@ 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_tag_idle(hctx);
-
-		if (set->ops->exit_hctx)
-			set->ops->exit_hctx(hctx, i);
-
-		blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
-		kfree(hctx->ctxs);
-		blk_mq_free_bitmap(&hctx->ctx_map);
+		blk_mq_exit_hctx(q, set, hctx, i);
 	}
-
 }
 
 static void blk_mq_free_hw_queues(struct request_queue *q,
@@ -1543,16 +1548,10 @@ static void blk_mq_free_hw_queues(struct request_queue *q,
 	}
 }
 
-static int blk_mq_init_hw_queues(struct request_queue *q,
-		struct blk_mq_tag_set *set)
+static int blk_mq_init_hctx(struct request_queue *q,
+		struct blk_mq_tag_set *set,
+		struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
 {
-	struct blk_mq_hw_ctx *hctx;
-	unsigned int i;
-
-	/*
-	 * Initialize hardware queues
-	 */
-	queue_for_each_hw_ctx(q, hctx, i) {
 	int node;
 
 	node = hctx->numa_node;
@@ -1564,7 +1563,7 @@ static int blk_mq_init_hw_queues(struct request_queue *q,
 	spin_lock_init(&hctx->lock);
 	INIT_LIST_HEAD(&hctx->dispatch);
 	hctx->queue = q;
-		hctx->queue_num = i;
+	hctx->queue_num = hctx_idx;
 	hctx->flags = set->flags;
 	hctx->cmd_size = set->cmd_size;
 
@@ -1572,7 +1571,7 @@ static int blk_mq_init_hw_queues(struct request_queue *q,
 					blk_mq_hctx_notify, hctx);
 	blk_mq_register_cpu_notifier(&hctx->cpu_notifier);
 
-		hctx->tags = set->tags[i];
+	hctx->tags = set->tags[hctx_idx];
 
 	/*
 	 * Allocate space for all possible cpus to avoid allocation at
@@ -1581,15 +1580,40 @@ static int blk_mq_init_hw_queues(struct request_queue *q,
 	hctx->ctxs = kmalloc_node(nr_cpu_ids * sizeof(void *),
 					GFP_KERNEL, node);
 	if (!hctx->ctxs)
-			break;
+		goto unregister_cpu_notifier;
 
 	if (blk_mq_alloc_bitmap(&hctx->ctx_map, node))
-			break;
+		goto free_ctxs;
 
 	hctx->nr_ctx = 0;
 
 	if (set->ops->init_hctx &&
-		    set->ops->init_hctx(hctx, set->driver_data, i))
+	    set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
+		goto free_bitmap;
+
+	return 0;
+
+ free_bitmap:
+	blk_mq_free_bitmap(&hctx->ctx_map);
+ free_ctxs:
+	kfree(hctx->ctxs);
+ unregister_cpu_notifier:
+	blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
+
+	return -1;
+}
+
+static int blk_mq_init_hw_queues(struct request_queue *q,
+		struct blk_mq_tag_set *set)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned int i;
+
+	/*
+	 * Initialize hardware queues
+	 */
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (blk_mq_init_hctx(q, set, hctx, i))
 			break;
 	}