[PATCHv2 7/7] nvme: export controller reconnect event count via sysfs

[Nilay Shroff]

When an NVMe-oF link goes down, the driver attempts to recover the
connection by repeatedly reconnecting to the remote controller at
configured intervals. A maximum number of reconnect attempts is also
configured, after which recovery stops and the controller is removed
if the connection cannot be re-established.

The driver maintains a counter, nr_reconnects, which is incremented on
each reconnect attempt. Currently, this counter is only reported via
kernel log messages and is not exposed to userspace. Since dmesg is a
circular buffer, this information may be lost over time.

Expose the nr_reconnects counter via a new sysfs attribute, reconnect_
events, to provide persistent visibility into the number of reconnect
attempts made by the host. This information can help users diagnose
unstable links or connectivity issues.

This counter can also be consumed by monitoring tools such as nvme-top
to improve controller-level observability.

Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
---
 drivers/nvme/host/sysfs.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
index 7958fe998139..0b3fdd55ba30 100644
--- a/drivers/nvme/host/sysfs.c
+++ b/drivers/nvme/host/sysfs.c
@@ -667,6 +667,15 @@ static ssize_t reset_events_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(reset_events);
 
+static ssize_t reconnect_events_show(struct device *dev,
+		   struct device_attribute *attr, char *buf)
+{
+	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%u\n", ctrl->nr_reconnects);
+}
+static DEVICE_ATTR_RO(reconnect_events);
+
 #ifdef CONFIG_NVME_HOST_AUTH
 static ssize_t nvme_ctrl_dhchap_secret_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
@@ -815,6 +824,7 @@ static struct attribute *nvme_dev_attrs[] = {
 	&dev_attr_adm_passthru_err_log_enabled.attr,
 	&dev_attr_adm_errors.attr,
 	&dev_attr_reset_events.attr,
+	&dev_attr_reconnect_events.attr,
 	NULL
 };
 
-- 
2.52.0