[PATCH 1/1] nvmet: allow setting model_number once

[Max Gurtovoy <mgurtovoy@nvidia.com>]

In case we have already established connection to nvmf target, it
shouldn't be allowed to change the model_number. E.g. if someone will
identify ctrl and get model_number of "my_model" later on will change
the model_numbel via configfs to "my_new_model" this will break the NVM
specification for "Get Log Page – Persistent Event Log" that refers to
Model Number as: "This field contains the same value as reported in the
Model Number field of the Identify Controller data structure, bytes
63:24."

Although it doesn't mentioned explicitly that this field can't be
changed, we can assume it.

So allow setting this field only once: using configfs or in the first
identify ctrl operation.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
---
 drivers/nvme/target/admin-cmd.c | 33 +++++++++++++------
 drivers/nvme/target/configfs.c  | 57 ++++++++++++++++++---------------
 drivers/nvme/target/core.c      |  2 +-
 drivers/nvme/target/nvmet.h     |  7 +---
 4 files changed, 57 insertions(+), 42 deletions(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index dc1ea468b182..6a3341b2091f 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -319,18 +319,25 @@ 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,
+static int 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;
+	int ret = 0;
 
-	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();
+	mutex_lock(&subsys->lock);
+	if (!subsys->model_number) {
+		subsys->model_number = kstrdup(NVMET_DEFAULT_CTRL_MODEL,
+					       GFP_KERNEL);
+		if (!subsys->model_number) {
+			ret = -ENOMEM;
+			goto out_unlock;
+		}
+	}
+	memcpy_and_pad(id->mn, sizeof(id->mn), subsys->model_number,
+		       strlen(subsys->model_number), ' ');
+out_unlock:
+	mutex_unlock(&subsys->lock);
+	return ret;
 }
 
 static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
@@ -339,6 +346,7 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 	struct nvme_id_ctrl *id;
 	u32 cmd_capsule_size;
 	u16 status = 0;
+	int ret;
 
 	id = kzalloc(sizeof(*id), GFP_KERNEL);
 	if (!id) {
@@ -353,7 +361,11 @@ 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));
-	nvmet_id_set_model_number(id, ctrl->subsys);
+	ret = nvmet_id_set_model_number(id, ctrl->subsys);
+	if (ret) {
+		status = NVME_SC_INTERNAL;
+		goto out_free;
+	}
 	memcpy_and_pad(id->fr, sizeof(id->fr),
 		       UTS_RELEASE, strlen(UTS_RELEASE), ' ');
 
@@ -461,6 +473,7 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 
 	status = nvmet_copy_to_sgl(req, 0, id, sizeof(*id));
 
+out_free:
 	kfree(id);
 out:
 	nvmet_req_complete(req, status);
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index c61ffd767062..ad1adcf30ee5 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -1120,16 +1120,14 @@ 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;
+	char *model = "";
 	int ret;
 
-	rcu_read_lock();
-	subsys_model = rcu_dereference(subsys->model);
-	if (subsys_model)
-		model = subsys_model->number;
+	mutex_lock(&subsys->lock);
+	if (subsys->model_number)
+		model = subsys->model_number;
 	ret = snprintf(page, PAGE_SIZE, "%s\n", model);
-	rcu_read_unlock();
+	mutex_unlock(&subsys->lock);
 
 	return ret;
 }
@@ -1144,40 +1142,49 @@ 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;
 
+	down_write(&nvmet_config_sem);
+	mutex_lock(&subsys->lock);
+	if (subsys->model_number) {
+		pr_err("Can't set model number. %s is already assigned\n",
+		       subsys->model_number);
+		count = -EINVAL;
+		goto out_unlock;
+	}
+
 	len = strcspn(page, "\n");
-	if (!len)
-		return -EINVAL;
+	if (!len) {
+		count = -EINVAL;
+		goto out_unlock;
+	}
 
 	for (pos = 0; pos < len; pos++) {
-		if (!nvmet_is_ascii(page[pos]))
-			return -EINVAL;
+		if (!nvmet_is_ascii(page[pos])) {
+			count = -EINVAL;
+			goto out_unlock;
+		}
 	}
 
 	new_model_number = kmemdup_nul(page, len, GFP_KERNEL);
-	if (!new_model_number)
-		return -ENOMEM;
+	if (!new_model_number) {
+		count = -ENOMEM;
+		goto out_unlock;
+	}
 
-	new_model = kzalloc(sizeof(*new_model) + len + 1, GFP_KERNEL);
-	if (!new_model) {
+	subsys->model_number = kstrdup(new_model_number, GFP_KERNEL);
+	if (!subsys->model_number) {
+		count = -ENOMEM;
 		kfree(new_model_number);
-		return -ENOMEM;
+		goto out_unlock;
 	}
-	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));
+	kfree(new_model_number);
+out_unlock:
 	mutex_unlock(&subsys->lock);
 	up_write(&nvmet_config_sem);
 
-	kfree_rcu(new_model, rcuhead);
-	kfree(new_model_number);
-
 	return count;
 }
 CONFIGFS_ATTR(nvmet_subsys_, attr_model);
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 8ce4d59cc9e7..c7af907912f2 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -1521,7 +1521,7 @@ static void nvmet_subsys_free(struct kref *ref)
 	nvmet_passthru_subsys_free(subsys);
 
 	kfree(subsys->subsysnqn);
-	kfree_rcu(subsys->model, rcuhead);
+	kfree(subsys->model_number);
 	kfree(subsys);
 }
 
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 592763732065..aac741bf378c 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -208,11 +208,6 @@ struct nvmet_ctrl {
 	bool			pi_support;
 };
 
-struct nvmet_subsys_model {
-	struct rcu_head		rcuhead;
-	char			number[];
-};
-
 struct nvmet_subsys {
 	enum nvme_subsys_type	type;
 
@@ -242,7 +237,7 @@ struct nvmet_subsys {
 	struct config_group	namespaces_group;
 	struct config_group	allowed_hosts_group;
 
-	struct nvmet_subsys_model	__rcu *model;
+	char			*model_number;
 
 #ifdef CONFIG_NVME_TARGET_PASSTHRU
 	struct nvme_ctrl	*passthru_ctrl;
-- 
2.25.4


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