nvmet: make ctrl model configurable

This patch adds a new target subsys attribute which allows user to
optionally specify model name which then used in the
nvmet_execute_identify_ctrl() to fill up the nvme_id_ctrl structure.

The default value for the model is set to "Linux" for backward
compatibility.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Mark Ruijter <MRuijter@onestopsystems.com>
[chaitanya.kulkarni@wdc.com
 *Use macro for default model, coding style fixes.
 *Use RCU for accessing model in for configfs and in
  nvmet_execute_identify_ctrl().
]
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/target/admin-cmd.c

@@ -322,12 +322,25 @@ static void nvmet_execute_get_log_page(struct nvmet_req *req)
 	nvmet_req_complete(req, NVME_SC_INVALID_FIELD | NVME_SC_DNR);
 }
 
+static void nvmet_id_set_model_number(struct nvme_id_ctrl *id,
+				      struct nvmet_subsys *subsys)
+{
+	const char *model = NVMET_DEFAULT_CTRL_MODEL;
+	struct nvmet_subsys_model *subsys_model;
+
+	rcu_read_lock();
+	subsys_model = rcu_dereference(subsys->model);
+	if (subsys_model)
+		model = subsys_model->number;
+	memcpy_and_pad(id->mn, sizeof(id->mn), model, strlen(model), ' ');
+	rcu_read_unlock();
+}
+
 static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 {
 	struct nvmet_ctrl *ctrl = req->sq->ctrl;
 	struct nvme_id_ctrl *id;
 	u16 status = 0;
-	const char model[] = "Linux";
 
 	id = kzalloc(sizeof(*id), GFP_KERNEL);
 	if (!id) {
@@ -342,7 +355,7 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 	memset(id->sn, ' ', sizeof(id->sn));
 	bin2hex(id->sn, &ctrl->subsys->serial,
 		min(sizeof(ctrl->subsys->serial), sizeof(id->sn) / 2));
-	memcpy_and_pad(id->mn, sizeof(id->mn), model, sizeof(model) - 1, ' ');
+	nvmet_id_set_model_number(id, ctrl->subsys);
 	memcpy_and_pad(id->fr, sizeof(id->fr),
 		       UTS_RELEASE, strlen(UTS_RELEASE), ' ');
 

drivers/nvme/target/configfs.c

@@ -919,12 +919,78 @@ static ssize_t nvmet_subsys_attr_cntlid_max_store(struct config_item *item,
 }
 CONFIGFS_ATTR(nvmet_subsys_, attr_cntlid_max);
 
+static ssize_t nvmet_subsys_attr_model_show(struct config_item *item,
+					    char *page)
+{
+	struct nvmet_subsys *subsys = to_subsys(item);
+	struct nvmet_subsys_model *subsys_model;
+	char *model = NVMET_DEFAULT_CTRL_MODEL;
+	int ret;
+
+	rcu_read_lock();
+	subsys_model = rcu_dereference(subsys->model);
+	if (subsys_model)
+		model = subsys_model->number;
+	ret = snprintf(page, PAGE_SIZE, "%s\n", model);
+	rcu_read_unlock();
+
+	return ret;
+}
+
+/* See Section 1.5 of NVMe 1.4 */
+static bool nvmet_is_ascii(const char c)
+{
+	return c >= 0x20 && c <= 0x7e;
+}
+
+static ssize_t nvmet_subsys_attr_model_store(struct config_item *item,
+					     const char *page, size_t count)
+{
+	struct nvmet_subsys *subsys = to_subsys(item);
+	struct nvmet_subsys_model *new_model;
+	char *new_model_number;
+	int pos = 0, len;
+
+	len = strcspn(page, "\n");
+	if (!len)
+		return -EINVAL;
+
+	for (pos = 0; pos < len; pos++) {
+		if (!nvmet_is_ascii(page[pos]))
+			return -EINVAL;
+	}
+
+	new_model_number = kstrndup(page, len, GFP_KERNEL);
+	if (!new_model_number)
+		return -ENOMEM;
+
+	new_model = kzalloc(sizeof(*new_model) + len + 1, GFP_KERNEL);
+	if (!new_model) {
+		kfree(new_model_number);
+		return -ENOMEM;
+	}
+	memcpy(new_model->number, new_model_number, len);
+
+	down_write(&nvmet_config_sem);
+	mutex_lock(&subsys->lock);
+	new_model = rcu_replace_pointer(subsys->model, new_model,
+					mutex_is_locked(&subsys->lock));
+	mutex_unlock(&subsys->lock);
+	up_write(&nvmet_config_sem);
+
+	kfree_rcu(new_model, rcuhead);
+
+	return count;
+}
+CONFIGFS_ATTR(nvmet_subsys_, attr_model);
+
 static struct configfs_attribute *nvmet_subsys_attrs[] = {
 	&nvmet_subsys_attr_attr_allow_any_host,
 	&nvmet_subsys_attr_attr_version,
 	&nvmet_subsys_attr_attr_serial,
 	&nvmet_subsys_attr_attr_cntlid_min,
 	&nvmet_subsys_attr_attr_cntlid_max,
+	&nvmet_subsys_attr_attr_model,
 	NULL,
 };
 

drivers/nvme/target/core.c

@@ -1461,6 +1461,7 @@ static void nvmet_subsys_free(struct kref *ref)
 	WARN_ON_ONCE(!list_empty(&subsys->namespaces));
 
 	kfree(subsys->subsysnqn);
+	kfree_rcu(subsys->model, rcuhead);
 	kfree(subsys);
 }
 

drivers/nvme/target/nvmet.h

@@ -23,6 +23,7 @@
 #define NVMET_ASYNC_EVENTS		4
 #define NVMET_ERROR_LOG_SLOTS		128
 #define NVMET_NO_ERROR_LOC		((u16)-1)
+#define NVMET_DEFAULT_CTRL_MODEL	"Linux"
 
 /*
  * Supported optional AENs:
@@ -202,6 +203,11 @@ struct nvmet_ctrl {
 	struct nvme_error_slot	slots[NVMET_ERROR_LOG_SLOTS];
 };
 
+struct nvmet_subsys_model {
+	struct rcu_head		rcuhead;
+	char			number[];
+};
+
 struct nvmet_subsys {
 	enum nvme_subsys_type	type;
 
@@ -229,6 +235,8 @@ struct nvmet_subsys {
 
 	struct config_group	namespaces_group;
 	struct config_group	allowed_hosts_group;
+
+	struct nvmet_subsys_model	__rcu *model;
 };
 
 static inline struct nvmet_subsys *to_subsys(struct config_item *item)