UBI: get device when opening volume

When a volume is opened, get its kref via get_device() call.
And put the reference when closing the volume. With this, we
may have a bit saner volume delete.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/cdev.c

@@ -635,9 +635,12 @@ static int ubi_cdev_ioctl(struct inode *inode, struct file *file,
 		}
 
 		err = ubi_remove_volume(desc);
-		if (err)
-			ubi_close_volume(desc);
-
+		/*
+		 * The volume is deleted, and the 'struct ubi_volume' object
+		 * will be freed when 'ubi_close_volume()' will call
+		 * 'put_device()'.
+		 */
+		ubi_close_volume(desc);
 		break;
 	}
 

drivers/mtd/ubi/kapi.c

@@ -156,6 +156,7 @@ struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode)
 		vol->exclusive = 1;
 		break;
 	}
+	get_device(&vol->dev);
 	spin_unlock(&ubi->volumes_lock);
 
 	desc->vol = vol;
@@ -274,6 +275,7 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
 	spin_unlock(&vol->ubi->volumes_lock);
 
 	kfree(desc);
+	put_device(&vol->dev);
 	module_put(THIS_MODULE);
 }
 EXPORT_SYMBOL_GPL(ubi_close_volume);

drivers/mtd/ubi/vmt.c

@@ -435,7 +435,6 @@ int ubi_remove_volume(struct ubi_volume_desc *desc)
 	vol->eba_tbl = NULL;
 	cdev_del(&vol->cdev);
 	volume_sysfs_close(vol);
-	kfree(desc);
 
 	spin_lock(&ubi->volumes_lock);
 	ubi->rsvd_pebs -= reserved_pebs;
@@ -453,10 +452,6 @@ int ubi_remove_volume(struct ubi_volume_desc *desc)
 	spin_unlock(&ubi->volumes_lock);
 
 	paranoid_check_volumes(ubi);
-	mutex_unlock(&ubi->volumes_mutex);
-	module_put(THIS_MODULE);
-	return 0;
-
 out:
 	mutex_unlock(&ubi->volumes_mutex);
 	return err;