nvme: fix per-namespace chardev deletion

Decrease reference count of chardevice during char device deletion in
order to fix a memory leak.  Add a release callabck for the device
associated chardev and move ida_simple_remove into the release function.

Fixes: 2637baed ("nvme: introduce generic per-namespace chardev")
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Suggested-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Adam Manzanares <a.manzanares@samsung.com>
Reviewed-by: Javier González <javier@javigon.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -3548,10 +3548,15 @@ static int __nvme_check_ids(struct nvme_subsystem *subsys,
 	return 0;
 }
 
+static void nvme_cdev_rel(struct device *dev)
+{
+	ida_simple_remove(&nvme_ns_chr_minor_ida, MINOR(dev->devt));
+}
+
 void nvme_cdev_del(struct cdev *cdev, struct device *cdev_device)
 {
 	cdev_device_del(cdev, cdev_device);
-	ida_simple_remove(&nvme_ns_chr_minor_ida, MINOR(cdev_device->devt));
+	put_device(cdev_device);
 }
 
 int nvme_cdev_add(struct cdev *cdev, struct device *cdev_device,
@@ -3564,14 +3569,14 @@ int nvme_cdev_add(struct cdev *cdev, struct device *cdev_device,
 		return minor;
 	cdev_device->devt = MKDEV(MAJOR(nvme_ns_chr_devt), minor);
 	cdev_device->class = nvme_ns_chr_class;
+	cdev_device->release = nvme_cdev_rel;
 	device_initialize(cdev_device);
 	cdev_init(cdev, fops);
 	cdev->owner = owner;
 	ret = cdev_device_add(cdev, cdev_device);
-	if (ret) {
+	if (ret)
 		put_device(cdev_device);
-		ida_simple_remove(&nvme_ns_chr_minor_ida, minor);
-	}
+
 	return ret;
 }
 
@@ -3603,11 +3608,9 @@ static int nvme_add_ns_cdev(struct nvme_ns *ns)
 			   ns->ctrl->instance, ns->head->instance);
 	if (ret)
 		return ret;
-	ret = nvme_cdev_add(&ns->cdev, &ns->cdev_device, &nvme_ns_chr_fops,
+
+	return nvme_cdev_add(&ns->cdev, &ns->cdev_device, &nvme_ns_chr_fops,
 			     ns->ctrl->ops->module);
-	if (ret)
-		kfree_const(ns->cdev_device.kobj.name);
-	return ret;
 }
 
 static struct nvme_ns_head *nvme_alloc_ns_head(struct nvme_ctrl *ctrl,

drivers/nvme/host/multipath.c

@@ -431,8 +431,6 @@ static int nvme_add_ns_head_cdev(struct nvme_ns_head *head)
 		return ret;
 	ret = nvme_cdev_add(&head->cdev, &head->cdev_device,
 			    &nvme_ns_head_chr_fops, THIS_MODULE);
-	if (ret)
-		kfree_const(head->cdev_device.kobj.name);
 	return ret;
 }