nvme: read the subsystem NQN from Identify Controller

NVMe 1.2.1 or later requires controllers to provide a subsystem NQN in the
Identify controller data structures. Use this NQN for the subsysnqn
sysfs attribute by storing it in the nvme_ctrl structure after verifying
it. For older controllers we generate a "fake" NQN per non-normative
text in the NVMe 1.3 spec.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Keith Busch <[e-mail]>
Reviewed-by: Johannes Thumshirn <[e-mail]>
Signed-off-by: Sagi Grimberg <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/nvme/host/core.c

···
 		string_matches(id->fr, q->fr, sizeof(id->fr));
 }
 
+static void nvme_init_subnqn(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
+{
+	size_t nqnlen;
+	int off;
+
+	nqnlen = strnlen(id->subnqn, NVMF_NQN_SIZE);
+	if (nqnlen > 0 && nqnlen < NVMF_NQN_SIZE) {
+		strcpy(ctrl->subnqn, id->subnqn);
+		return;
+	}
+
+	if (ctrl->vs >= NVME_VS(1, 2, 1))
+		dev_warn(ctrl->device, "missing or invalid SUBNQN field.\n");
+
+	/* Generate a "fake" NQN per Figure 254 in NVMe 1.3 + ECN 001 */
+	off = snprintf(ctrl->subnqn, NVMF_NQN_SIZE,
+			"nqn.2014.08.org.nvmexpress:%4x%4x",
+			le16_to_cpu(id->vid), le16_to_cpu(id->ssvid));
+	memcpy(ctrl->subnqn + off, id->sn, sizeof(id->sn));
+	off += sizeof(id->sn);
+	memcpy(ctrl->subnqn + off, id->mn, sizeof(id->mn));
+	off += sizeof(id->mn);
+	memset(ctrl->subnqn + off, 0, sizeof(ctrl->subnqn) - off);
+}
+
 /*
  * Initialize the cached copies of the Identify data and various controller
  * register in our nvme_ctrl structure.  This should be called as soon as
···
 		dev_err(ctrl->device, "Identify Controller failed (%d)\n", ret);
 		return -EIO;
 	}
+
+	nvme_init_subnqn(ctrl, id);
 
 	if (!ctrl->identified) {
 		/*
···
 {
 	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
 
-	return snprintf(buf, PAGE_SIZE, "%s\n",
-			ctrl->ops->get_subsysnqn(ctrl));
+	return snprintf(buf, PAGE_SIZE, "%s\n", ctrl->subnqn);
 }
 static DEVICE_ATTR(subsysnqn, S_IRUGO, nvme_sysfs_show_subsysnqn, NULL);
 
···
 			return 0;
 	}
 
-	CHECK_ATTR(ctrl, a, subsysnqn);
 	CHECK_ATTR(ctrl, a, address);
 
 	return a->mode;

drivers/nvme/host/fabrics.c

···
 EXPORT_SYMBOL_GPL(nvmf_get_address);
 
 /**
- * nvmf_get_subsysnqn() - Get subsystem NQN
- * @ctrl:	Host NVMe controller instance which we got the NQN
- */
-const char *nvmf_get_subsysnqn(struct nvme_ctrl *ctrl)
-{
-	return ctrl->opts->subsysnqn;
-}
-EXPORT_SYMBOL_GPL(nvmf_get_subsysnqn);
-
-/**
  * nvmf_reg_read32() -  NVMe Fabrics "Property Get" API function.
  * @ctrl:	Host NVMe controller instance maintaining the admin
  *		queue used to submit the property read command to

drivers/nvme/host/fabrics.h

···
 int nvmf_register_transport(struct nvmf_transport_ops *ops);
 void nvmf_unregister_transport(struct nvmf_transport_ops *ops);
 void nvmf_free_options(struct nvmf_ctrl_options *opts);
-const char *nvmf_get_subsysnqn(struct nvme_ctrl *ctrl);
 int nvmf_get_address(struct nvme_ctrl *ctrl, char *buf, int size);
 bool nvmf_should_reconnect(struct nvme_ctrl *ctrl);
 

drivers/nvme/host/fc.c

···
 	.free_ctrl		= nvme_fc_nvme_ctrl_freed,
 	.submit_async_event	= nvme_fc_submit_async_event,
 	.delete_ctrl		= nvme_fc_del_nvme_ctrl,
-	.get_subsysnqn		= nvmf_get_subsysnqn,
 	.get_address		= nvmf_get_address,
 };
 

drivers/nvme/host/nvme.h

···
 	char serial[20];
 	char model[40];
 	char firmware_rev[8];
+	char subnqn[NVMF_NQN_SIZE];
 	u16 cntlid;
 
 	u32 ctrl_config;
···
 	void (*free_ctrl)(struct nvme_ctrl *ctrl);
 	void (*submit_async_event)(struct nvme_ctrl *ctrl, int aer_idx);
 	int (*delete_ctrl)(struct nvme_ctrl *ctrl);
-	const char *(*get_subsysnqn)(struct nvme_ctrl *ctrl);
 	int (*get_address)(struct nvme_ctrl *ctrl, char *buf, int size);
 };
 

drivers/nvme/host/rdma.c

···
 	.free_ctrl		= nvme_rdma_free_ctrl,
 	.submit_async_event	= nvme_rdma_submit_async_event,
 	.delete_ctrl		= nvme_rdma_del_ctrl,
-	.get_subsysnqn		= nvmf_get_subsysnqn,
 	.get_address		= nvmf_get_address,
 };
 

drivers/nvme/target/loop.c

···
 	.free_ctrl		= nvme_loop_free_ctrl,
 	.submit_async_event	= nvme_loop_submit_async_event,
 	.delete_ctrl		= nvme_loop_del_ctrl,
-	.get_subsysnqn		= nvmf_get_subsysnqn,
 };
 
 static int nvme_loop_create_io_queues(struct nvme_loop_ctrl *ctrl)