nvmet: make sn stable once connection was established

Once some host has connected to the target, make sure that the serial
number is stable and cannot be changed.

Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Noam Gottlieb <ngottlieb@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 22 insertions, 5 deletions

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 027b28aaf7cd..a13da86fb374 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -1044,12 +1044,18 @@ static ssize_t nvmet_subsys_attr_serial_show(struct config_item *item,
 	return snprintf(page, PAGE_SIZE, "%s\n", subsys->serial);
 }
 
-static ssize_t nvmet_subsys_attr_serial_store(struct config_item *item,
-					      const char *page, size_t count)
+static ssize_t
+nvmet_subsys_attr_serial_store_locked(struct nvmet_subsys *subsys,
+		const char *page, size_t count)
 {
-	struct nvmet_subsys *subsys = to_subsys(item);
 	int pos, len = strcspn(page, "\n");
 
+	if (subsys->subsys_discovered) {
+		pr_err("Can't set serial number. %s is already assigned\n",
+		       subsys->serial);
+		return -EINVAL;
+	}
+
 	if (!len || len > NVMET_SN_MAX_SIZE) {
 		pr_err("Serial Number can not be empty or exceed %d Bytes\n",
 		       NVMET_SN_MAX_SIZE);
@@ -1063,13 +1069,24 @@ static ssize_t nvmet_subsys_attr_serial_store(struct config_item *item,
 		}
 	}
 
+	memcpy_and_pad(subsys->serial, NVMET_SN_MAX_SIZE, page, len, ' ');
+
+	return count;
+}
+
+static ssize_t nvmet_subsys_attr_serial_store(struct config_item *item,
+					      const char *page, size_t count)
+{
+	struct nvmet_subsys *subsys = to_subsys(item);
+	ssize_t ret;
+
 	down_write(&nvmet_config_sem);
 	mutex_lock(&subsys->lock);
-	memcpy_and_pad(subsys->serial, NVMET_SN_MAX_SIZE, page, len, ' ');
+	ret = nvmet_subsys_attr_serial_store_locked(subsys, page, count);
 	mutex_unlock(&subsys->lock);
 	up_write(&nvmet_config_sem);
 
-	return count;
+	return ret;
 }
 CONFIGFS_ATTR(nvmet_subsys_, attr_serial);