block/blk-mq-tag.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 32e8dbb..8d4b4f0 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -232,6 +232,27 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
 	return bs;
 }
 
+static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt);
+
+static void print_hctx_tags_usage(struct blk_mq_hw_ctx *hctx)
+{
+	unsigned int free, res;
+	struct blk_mq_tags *tags = hctx->tags;
+
+	if (!tags)
+		return;
+
+	printk("queue_num=%d, nr_tags=%u, reserved_tags=%u, bits_per_word=%u\n",
+	       hctx->queue_num, tags->nr_tags, tags->nr_reserved_tags,
+	       tags->bitmap_tags.bits_per_word);
+
+	free = bt_unused_tags(&tags->bitmap_tags);
+	res = bt_unused_tags(&tags->breserved_tags);
+
+	printk("nr_free=%u, nr_reserved=%u\n", free, res);
+	printk("active_queues=%u\n", atomic_read(&tags->active_queues));
+}
+
 static int bt_get(struct blk_mq_alloc_data *data,
 		struct blk_mq_bitmap_tags *bt,
 		struct blk_mq_hw_ctx *hctx,
@@ -245,6 +266,10 @@ static int bt_get(struct blk_mq_alloc_data *data,
 	if (tag != -1)
 		return tag;
 
+	printk("\n%s: __bt_get() returned -1\n", __func__);
+	print_hctx_tags_usage(hctx);
+	dump_stack();
+
 	if (!(data->gfp & __GFP_WAIT))
 		return -1;
 
@@ -256,6 +281,9 @@ static int bt_get(struct blk_mq_alloc_data *data,
 		if (tag != -1)
 			break;
 
+		printk("%s: __bt_get() _still_ returned -1\n", __func__);
+		print_hctx_tags_usage(hctx);
+
 		/*
 		 * We're out of tags on this hardware queue, kick any
 		 * pending IO submits before going to sleep waiting for