nvme: free sq/cq dbbuf pointers when dbbuf set fails

If Doorbell Buffer Config command fails even 'dev->dbbuf_dbs != NULL'
which means OACS indicates that NVME_CTRL_OACS_DBBUF_SUPP is set,
nvme_dbbuf_update_and_check_event() will check event even it's not been
successfully set.

This patch fixes mismatch among dbbuf for sq/cqs in case that dbbuf
command fails.
Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/pci.c

@@ -292,9 +292,21 @@ static void nvme_dbbuf_init(struct nvme_dev *dev,
 	nvmeq->dbbuf_cq_ei = &dev->dbbuf_eis[cq_idx(qid, dev->db_stride)];
 }
 
+static void nvme_dbbuf_free(struct nvme_queue *nvmeq)
+{
+	if (!nvmeq->qid)
+		return;
+
+	nvmeq->dbbuf_sq_db = NULL;
+	nvmeq->dbbuf_cq_db = NULL;
+	nvmeq->dbbuf_sq_ei = NULL;
+	nvmeq->dbbuf_cq_ei = NULL;
+}
+
 static void nvme_dbbuf_set(struct nvme_dev *dev)
 {
 	struct nvme_command c;
+	unsigned int i;
 
 	if (!dev->dbbuf_dbs)
 		return;
@@ -308,6 +320,9 @@ static void nvme_dbbuf_set(struct nvme_dev *dev)
 		dev_warn(dev->ctrl.device, "unable to set dbbuf\n");
 		/* Free memory and continue on */
 		nvme_dbbuf_dma_free(dev);
+
+		for (i = 1; i <= dev->online_queues; i++)
+			nvme_dbbuf_free(&dev->queues[i]);
 	}
 }