nvme-pci: simplify nvme_dbbuf_dma_alloc

Move the OACS check and the error checking into nvme_dbbuf_dma_alloc so
that an upcoming second caller doesn't have to duplicate this boilerplate
code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

drivers/nvme/host/pci.c

@@ -239,10 +239,13 @@ static inline unsigned int nvme_dbbuf_size(struct nvme_dev *dev)
 	return dev->nr_allocated_queues * 8 * dev->db_stride;
 }
 
-static int nvme_dbbuf_dma_alloc(struct nvme_dev *dev)
+static void nvme_dbbuf_dma_alloc(struct nvme_dev *dev)
 {
 	unsigned int mem_size = nvme_dbbuf_size(dev);
 
+	if (!(dev->ctrl.oacs & NVME_CTRL_OACS_DBBUF_SUPP))
+		return;
+
 	if (dev->dbbuf_dbs) {
 		/*
 		 * Clear the dbbuf memory so the driver doesn't observe stale
@@ -250,25 +253,27 @@ static int nvme_dbbuf_dma_alloc(struct nvme_dev *dev)
 		 */
 		memset(dev->dbbuf_dbs, 0, mem_size);
 		memset(dev->dbbuf_eis, 0, mem_size);
-		return 0;
+		return;
 	}
 
 	dev->dbbuf_dbs = dma_alloc_coherent(dev->dev, mem_size,
 					    &dev->dbbuf_dbs_dma_addr,
 					    GFP_KERNEL);
 	if (!dev->dbbuf_dbs)
-		return -ENOMEM;
+		goto fail;
 	dev->dbbuf_eis = dma_alloc_coherent(dev->dev, mem_size,
 					    &dev->dbbuf_eis_dma_addr,
 					    GFP_KERNEL);
-	if (!dev->dbbuf_eis) {
-		dma_free_coherent(dev->dev, mem_size,
-				  dev->dbbuf_dbs, dev->dbbuf_dbs_dma_addr);
-		dev->dbbuf_dbs = NULL;
-		return -ENOMEM;
-	}
+	if (!dev->dbbuf_eis)
+		goto fail_free_dbbuf_dbs;
+	return;
 
-	return 0;
+fail_free_dbbuf_dbs:
+	dma_free_coherent(dev->dev, mem_size, dev->dbbuf_dbs,
+			  dev->dbbuf_dbs_dma_addr);
+	dev->dbbuf_dbs = NULL;
+fail:
+	dev_warn(dev->dev, "unable to allocate dma for dbbuf\n");
 }
 
 static void nvme_dbbuf_dma_free(struct nvme_dev *dev)
@@ -2855,12 +2860,7 @@ static void nvme_reset_work(struct work_struct *work)
 	if (result)
 		goto out;
 
-	if (dev->ctrl.oacs & NVME_CTRL_OACS_DBBUF_SUPP) {
-		result = nvme_dbbuf_dma_alloc(dev);
-		if (result)
-			dev_warn(dev->dev,
-				 "unable to allocate dma for dbbuf\n");
-	}
+	nvme_dbbuf_dma_alloc(dev);
 
 	if (dev->ctrl.hmpre) {
 		result = nvme_setup_host_mem(dev);