[PATCH] NVMe: User initiated rescan

[Keith Busch]

This provides user ioctl and sysfs methods that can be used to request
the driver rescan a controller and its namespaces. This is less harsh
than doing a controller reset, which temporarily halts all IO just to
surface a newly attached namespace.

This is mainly useful for controllers that implement namespace management,
but do not support the namespace notify change asynchronous event
notification.

Signed-off-by: Keith Busch <keith.busch at intel.com>
---
 drivers/nvme/host/core.c        | 22 ++++++++++++++++++++--
 drivers/nvme/host/nvme.h        |  2 +-
 include/uapi/linux/nvme_ioctl.h |  1 +
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 2df0351d..b85c4b1 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1216,6 +1216,8 @@ static long nvme_dev_ioctl(struct file *file, unsigned int cmd,
 		return ctrl->ops->reset_ctrl(ctrl);
 	case NVME_IOCTL_SUBSYS_RESET:
 		return nvme_reset_subsystem(ctrl);
+	case NVME_IOCTL_RESCAN:
+		return nvme_queue_scan(ctrl);
 	default:
 		return -ENOTTY;
 	}
@@ -1243,6 +1245,20 @@ static ssize_t nvme_sysfs_reset(struct device *dev,
 }
 static DEVICE_ATTR(reset_controller, S_IWUSR, NULL, nvme_sysfs_reset);
 
+static ssize_t nvme_sysfs_rescan(struct device *dev,
+				struct device_attribute *attr, const char *buf,
+				size_t count)
+{
+	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+	int ret;
+
+	ret = nvme_queue_scan(ctrl);
+	if (ret < 0)
+		return ret;
+	return count;
+}
+static DEVICE_ATTR(rescan_controller, S_IWUSR, NULL, nvme_sysfs_rescan);
+
 static ssize_t wwid_show(struct device *dev, struct device_attribute *attr,
 								char *buf)
 {
@@ -1346,6 +1362,7 @@ nvme_show_int_function(cntlid);
 
 static struct attribute *nvme_dev_attrs[] = {
 	&dev_attr_reset_controller.attr,
+	&dev_attr_rescan_controller.attr,
 	&dev_attr_model.attr,
 	&dev_attr_serial.attr,
 	&dev_attr_firmware_rev.attr,
@@ -1569,14 +1586,15 @@ static void nvme_scan_work(struct work_struct *work)
 		ctrl->ops->post_scan(ctrl);
 }
 
-void nvme_queue_scan(struct nvme_ctrl *ctrl)
+int nvme_queue_scan(struct nvme_ctrl *ctrl)
 {
 	/*
 	 * Do not queue new scan work when a controller is reset during
 	 * removal.
 	 */
 	if (ctrl->state == NVME_CTRL_LIVE)
-		schedule_work(&ctrl->scan_work);
+		return schedule_work(&ctrl->scan_work);
+	return -EBUSY;
 }
 EXPORT_SYMBOL_GPL(nvme_queue_scan);
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 114b928..997b9ec 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -217,7 +217,7 @@ void nvme_uninit_ctrl(struct nvme_ctrl *ctrl);
 void nvme_put_ctrl(struct nvme_ctrl *ctrl);
 int nvme_init_identify(struct nvme_ctrl *ctrl);
 
-void nvme_queue_scan(struct nvme_ctrl *ctrl);
+int nvme_queue_scan(struct nvme_ctrl *ctrl);
 void nvme_remove_namespaces(struct nvme_ctrl *ctrl);
 
 #define NVME_NR_AERS	1
diff --git a/include/uapi/linux/nvme_ioctl.h b/include/uapi/linux/nvme_ioctl.h
index c4b2a3f..50ff21f 100644
--- a/include/uapi/linux/nvme_ioctl.h
+++ b/include/uapi/linux/nvme_ioctl.h
@@ -61,5 +61,6 @@ struct nvme_passthru_cmd {
 #define NVME_IOCTL_IO_CMD	_IOWR('N', 0x43, struct nvme_passthru_cmd)
 #define NVME_IOCTL_RESET	_IO('N', 0x44)
 #define NVME_IOCTL_SUBSYS_RESET	_IO('N', 0x45)
+#define NVME_IOCTL_RESCAN	_IO('N', 0x46)
 
 #endif /* _UAPI_LINUX_NVME_IOCTL_H */
-- 
2.7.2