nvme: code cleanup nvme_identify_ns_desc()

The function nvme_identify_ns_desc() has 3 levels of nesting which make
error message to exceeded > 80 char per line which is not aligned with
the kernel code standards and rest of the NVMe subsystem code.

Add a helper function to move the processing of the log when the
command is successful by reducing the nesting and keeping the
code < 80 char per line.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/host/core.c

@@ -1055,6 +1055,43 @@ static int nvme_identify_ctrl(struct nvme_ctrl *dev, struct nvme_id_ctrl **id)
 	return error;
 }
 
+static int nvme_process_ns_desc(struct nvme_ctrl *ctrl, struct nvme_ns_ids *ids,
+		struct nvme_ns_id_desc *cur)
+{
+	const char *warn_str = "ctrl returned bogus length:";
+	void *data = cur;
+
+	switch (cur->nidt) {
+	case NVME_NIDT_EUI64:
+		if (cur->nidl != NVME_NIDT_EUI64_LEN) {
+			dev_warn(ctrl->device, "%s %d for NVME_NIDT_EUI64\n",
+				 warn_str, cur->nidl);
+			return -1;
+		}
+		memcpy(ids->eui64, data + sizeof(*cur), NVME_NIDT_EUI64_LEN);
+		return NVME_NIDT_EUI64_LEN;
+	case NVME_NIDT_NGUID:
+		if (cur->nidl != NVME_NIDT_NGUID_LEN) {
+			dev_warn(ctrl->device, "%s %d for NVME_NIDT_NGUID\n",
+				 warn_str, cur->nidl);
+			return -1;
+		}
+		memcpy(ids->nguid, data + sizeof(*cur), NVME_NIDT_NGUID_LEN);
+		return NVME_NIDT_NGUID_LEN;
+	case NVME_NIDT_UUID:
+		if (cur->nidl != NVME_NIDT_UUID_LEN) {
+			dev_warn(ctrl->device, "%s %d for NVME_NIDT_UUID\n",
+				 warn_str, cur->nidl);
+			return -1;
+		}
+		uuid_copy(&ids->uuid, data + sizeof(*cur));
+		return NVME_NIDT_UUID_LEN;
+	default:
+		/* Skip unknown types */
+		return cur->nidl;
+	}
+}
+
 static int nvme_identify_ns_descs(struct nvme_ctrl *ctrl, unsigned nsid,
 		struct nvme_ns_ids *ids)
 {
@@ -1083,42 +1120,9 @@ static int nvme_identify_ns_descs(struct nvme_ctrl *ctrl, unsigned nsid,
 		if (cur->nidl == 0)
 			break;
 
-		switch (cur->nidt) {
-		case NVME_NIDT_EUI64:
-			if (cur->nidl != NVME_NIDT_EUI64_LEN) {
-				dev_warn(ctrl->device,
-					 "ctrl returned bogus length: %d for NVME_NIDT_EUI64\n",
-					 cur->nidl);
-				goto free_data;
-			}
-			len = NVME_NIDT_EUI64_LEN;
-			memcpy(ids->eui64, data + pos + sizeof(*cur), len);
-			break;
-		case NVME_NIDT_NGUID:
-			if (cur->nidl != NVME_NIDT_NGUID_LEN) {
-				dev_warn(ctrl->device,
-					 "ctrl returned bogus length: %d for NVME_NIDT_NGUID\n",
-					 cur->nidl);
+		len = nvme_process_ns_desc(ctrl, ids, cur);
+		if (len < 0)
 			goto free_data;
-			}
-			len = NVME_NIDT_NGUID_LEN;
-			memcpy(ids->nguid, data + pos + sizeof(*cur), len);
-			break;
-		case NVME_NIDT_UUID:
-			if (cur->nidl != NVME_NIDT_UUID_LEN) {
-				dev_warn(ctrl->device,
-					 "ctrl returned bogus length: %d for NVME_NIDT_UUID\n",
-					 cur->nidl);
-				goto free_data;
-			}
-			len = NVME_NIDT_UUID_LEN;
-			uuid_copy(&ids->uuid, data + pos + sizeof(*cur));
-			break;
-		default:
-			/* Skip unknown types */
-			len = cur->nidl;
-			break;
-		}
 
 		len += sizeof(*cur);
 	}