nvme: get rid of nvme_ctrl_list

Use the core chrdev code to set up the link between the character device
and the nvme controller.  This allows us to get rid of the global list
of all controllers, and also ensures that we have both a reference to
the controller and the transport module before the open method of the
character device is called.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sgi@grimberg.me>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>

drivers/nvme/host/core.c

@@ -52,9 +52,6 @@ static u8 nvme_max_retries = 5;
 module_param_named(max_retries, nvme_max_retries, byte, 0644);
 MODULE_PARM_DESC(max_retries, "max number of retries a command may have");
 
-static int nvme_char_major;
-module_param(nvme_char_major, int, 0);
-
 static unsigned long default_ps_max_latency_us = 100000;
 module_param(default_ps_max_latency_us, ulong, 0644);
 MODULE_PARM_DESC(default_ps_max_latency_us,
@@ -71,11 +68,8 @@ MODULE_PARM_DESC(streams, "turn on support for Streams write directives");
 struct workqueue_struct *nvme_wq;
 EXPORT_SYMBOL_GPL(nvme_wq);
 
-static LIST_HEAD(nvme_ctrl_list);
-static DEFINE_SPINLOCK(dev_list_lock);
-
 static DEFINE_IDA(nvme_instance_ida);
-
+static dev_t nvme_chr_devt;
 static struct class *nvme_class;
 
 static __le32 nvme_get_log_dw10(u8 lid, size_t size)
@@ -1031,20 +1025,12 @@ static int nvme_open(struct block_device *bdev, fmode_t mode)
 
 	if (!kref_get_unless_zero(&ns->kref))
 		return -ENXIO;
-	if (!try_module_get(ns->ctrl->ops->module)) {
-		kref_put(&ns->kref, nvme_free_ns);
-		return -ENXIO;
-	}
-
 	return 0;
 }
 
 static void nvme_release(struct gendisk *disk, fmode_t mode)
 {
-	struct nvme_ns *ns = disk->private_data;
-
-	module_put(ns->ctrl->ops->module);
-	nvme_put_ns(ns);
+	nvme_put_ns(disk->private_data);
 }
 
 static int nvme_getgeo(struct block_device *bdev, struct hd_geometry *geo)
@@ -1902,33 +1888,12 @@ EXPORT_SYMBOL_GPL(nvme_init_identify);
 
 static int nvme_dev_open(struct inode *inode, struct file *file)
 {
-	struct nvme_ctrl *ctrl;
-	int instance = iminor(inode);
-	int ret = -ENODEV;
-
-	spin_lock(&dev_list_lock);
-	list_for_each_entry(ctrl, &nvme_ctrl_list, node) {
-		if (ctrl->instance != instance)
-			continue;
-
-		if (!ctrl->admin_q) {
-			ret = -EWOULDBLOCK;
-			break;
-		}
-		if (!kobject_get_unless_zero(&ctrl->device->kobj))
-			break;
-		file->private_data = ctrl;
-		ret = 0;
-		break;
-	}
-	spin_unlock(&dev_list_lock);
-
-	return ret;
-}
+	struct nvme_ctrl *ctrl =
+		container_of(inode->i_cdev, struct nvme_ctrl, cdev);
 
-static int nvme_dev_release(struct inode *inode, struct file *file)
-{
-	nvme_put_ctrl(file->private_data);
+	if (!ctrl->admin_q)
+		return -EWOULDBLOCK;
+	file->private_data = ctrl;
 	return 0;
 }
 
@@ -1992,7 +1957,6 @@ static long nvme_dev_ioctl(struct file *file, unsigned int cmd,
 static const struct file_operations nvme_dev_fops = {
 	.owner		= THIS_MODULE,
 	.open		= nvme_dev_open,
-	.release	= nvme_dev_release,
 	.unlocked_ioctl	= nvme_dev_ioctl,
 	.compat_ioctl	= nvme_dev_ioctl,
 };
@@ -2703,11 +2667,7 @@ EXPORT_SYMBOL_GPL(nvme_start_ctrl);
 
 void nvme_uninit_ctrl(struct nvme_ctrl *ctrl)
 {
-	device_del(ctrl->device);
-
-	spin_lock(&dev_list_lock);
-	list_del(&ctrl->node);
-	spin_unlock(&dev_list_lock);
+	cdev_device_del(&ctrl->cdev, ctrl->device);
 }
 EXPORT_SYMBOL_GPL(nvme_uninit_ctrl);
 
@@ -2750,7 +2710,7 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
 
 	device_initialize(&ctrl->ctrl_device);
 	ctrl->device = &ctrl->ctrl_device;
-	ctrl->device->devt = MKDEV(nvme_char_major, ctrl->instance);
+	ctrl->device->devt = MKDEV(MAJOR(nvme_chr_devt), ctrl->instance);
 	ctrl->device->class = nvme_class;
 	ctrl->device->parent = ctrl->dev;
 	ctrl->device->groups = nvme_dev_attr_groups;
@@ -2759,16 +2719,15 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
 	ret = dev_set_name(ctrl->device, "nvme%d", ctrl->instance);
 	if (ret)
 		goto out_release_instance;
-	ret = device_add(ctrl->device);
+
+	cdev_init(&ctrl->cdev, &nvme_dev_fops);
+	ctrl->cdev.owner = ops->module;
+	ret = cdev_device_add(&ctrl->cdev, ctrl->device);
 	if (ret)
 		goto out_free_name;
 
 	ida_init(&ctrl->ns_ida);
 
-	spin_lock(&dev_list_lock);
-	list_add_tail(&ctrl->node, &nvme_ctrl_list);
-	spin_unlock(&dev_list_lock);
-
 	/*
 	 * Initialize latency tolerance controls.  The sysfs files won't
 	 * be visible to userspace unless the device actually supports APST.
@@ -2909,12 +2868,9 @@ int __init nvme_core_init(void)
 	if (!nvme_wq)
 		return -ENOMEM;
 
-	result = __register_chrdev(nvme_char_major, 0, NVME_MINORS, "nvme",
-							&nvme_dev_fops);
+	result = alloc_chrdev_region(&nvme_chr_devt, 0, NVME_MINORS, "nvme");
 	if (result < 0)
 		goto destroy_wq;
-	else if (result > 0)
-		nvme_char_major = result;
 
 	nvme_class = class_create(THIS_MODULE, "nvme");
 	if (IS_ERR(nvme_class)) {
@@ -2925,7 +2881,7 @@ int __init nvme_core_init(void)
 	return 0;
 
 unregister_chrdev:
-	__unregister_chrdev(nvme_char_major, 0, NVME_MINORS, "nvme");
+	unregister_chrdev_region(nvme_chr_devt, NVME_MINORS);
 destroy_wq:
 	destroy_workqueue(nvme_wq);
 	return result;
@@ -2934,7 +2890,7 @@ int __init nvme_core_init(void)
 void nvme_core_exit(void)
 {
 	class_destroy(nvme_class);
-	__unregister_chrdev(nvme_char_major, 0, NVME_MINORS, "nvme");
+	unregister_chrdev_region(nvme_chr_devt, NVME_MINORS);
 	destroy_workqueue(nvme_wq);
 }
 

drivers/nvme/host/nvme.h

@@ -15,6 +15,7 @@
 #define _NVME_H
 
 #include <linux/nvme.h>
+#include <linux/cdev.h>
 #include <linux/pci.h>
 #include <linux/kref.h>
 #include <linux/blk-mq.h>
@@ -134,7 +135,7 @@ struct nvme_ctrl {
 	struct mutex namespaces_mutex;
 	struct device ctrl_device;
 	struct device *device;	/* char device */
-	struct list_head node;
+	struct cdev cdev;
 	struct ida ns_ida;
 	struct work_struct reset_work;