nvmet: remove redundant subsysnqn field from ctrl

The subsysnqn field in the nvmet controller structure is redundant,
since the subsystem NQN can always be accessed via the controller's
subsystem reference. Remove this field to save memory and avoid
unnecessary duplication.

Signed-off-by: Max Gurtovoy <[e-mail]>
Signed-off-by: Keith Busch <[e-mail]>

drivers/nvme/target/auth.c

···
 	ret = crypto_shash_update(shash, buf, 1);
 	if (ret)
 		goto out;
-	ret = crypto_shash_update(shash, ctrl->subsysnqn,
-				  strlen(ctrl->subsysnqn));
+	ret = crypto_shash_update(shash, ctrl->subsys->subsysnqn,
+				  strlen(ctrl->subsys->subsysnqn));
 	if (ret)
 		goto out;
 	ret = crypto_shash_final(shash, response);
···
 	}
 
 	transformed_key = nvme_auth_transform_key(ctrl->ctrl_key,
-						ctrl->subsysnqn);
+						ctrl->subsys->subsysnqn);
 	if (IS_ERR(transformed_key)) {
 		ret = PTR_ERR(transformed_key);
 		goto out_free_tfm;
···
 	ret = crypto_shash_update(shash, "Controller", 10);
 	if (ret)
 		goto out;
-	ret = crypto_shash_update(shash, ctrl->subsysnqn,
-			    strlen(ctrl->subsysnqn));
+	ret = crypto_shash_update(shash, ctrl->subsys->subsysnqn,
+			    strlen(ctrl->subsys->subsysnqn));
 	if (ret)
 		goto out;
 	ret = crypto_shash_update(shash, buf, 1);
···
 		return;
 	}
 	ret = nvme_auth_generate_digest(sq->ctrl->shash_id, psk, psk_len,
-					sq->ctrl->subsysnqn,
+					sq->ctrl->subsys->subsysnqn,
 					sq->ctrl->hostnqn, &digest);
 	if (ret) {
 		pr_warn("%s: ctrl %d qid %d failed to generate digest, error %d\n",
···
 		goto out_free_digest;
 	}
 #ifdef CONFIG_NVME_TARGET_TCP_TLS
-	tls_key = nvme_tls_psk_refresh(NULL, sq->ctrl->hostnqn, sq->ctrl->subsysnqn,
-				       sq->ctrl->shash_id, tls_psk, psk_len, digest);
+	tls_key = nvme_tls_psk_refresh(NULL, sq->ctrl->hostnqn,
+				       sq->ctrl->subsys->subsysnqn,
+				       sq->ctrl->shash_id, tls_psk, psk_len,
+				       digest);
 	if (IS_ERR(tls_key)) {
 		pr_warn("%s: ctrl %d qid %d failed to refresh key, error %ld\n",
 			__func__, sq->ctrl->cntlid, sq->qid, PTR_ERR(tls_key));

drivers/nvme/target/core.c

···
 	INIT_WORK(&ctrl->fatal_err_work, nvmet_fatal_error_handler);
 	INIT_DELAYED_WORK(&ctrl->ka_work, nvmet_keep_alive_timer);
 
-	memcpy(ctrl->subsysnqn, args->subsysnqn, NVMF_NQN_SIZE);
 	memcpy(ctrl->hostnqn, args->hostnqn, NVMF_NQN_SIZE);
 
 	kref_init(&ctrl->ref);

drivers/nvme/target/nvmet.h

···
 	__le32			*changed_ns_list;
 	u32			nr_changed_ns;
 
-	char			subsysnqn[NVMF_NQN_FIELD_LEN];
 	char			hostnqn[NVMF_NQN_FIELD_LEN];
 
 	struct device		*p2p_client;

drivers/nvme/target/passthru.c

···
 	 * code path with duplicate ctrl subsysnqn. In order to prevent that we
 	 * mask the passthru-ctrl subsysnqn with the target ctrl subsysnqn.
 	 */
-	memcpy(id->subnqn, ctrl->subsysnqn, sizeof(id->subnqn));
+	memcpy(id->subnqn, ctrl->subsys->subsysnqn, sizeof(id->subnqn));
 
 	/* use fabric id-ctrl values */
 	id->ioccsz = cpu_to_le32((sizeof(struct nvme_command) +