btrfs_alloc_device
device = btrfs_alloc_device(NULL, &devid, NULL, device_path);
device = btrfs_alloc_device(NULL, &orig_dev->devid,
device = btrfs_alloc_device(fs_info, NULL, NULL, device_path);
device = btrfs_alloc_device(NULL, &devid, dev_uuid, NULL);
device = btrfs_alloc_device(NULL, &devid,
struct btrfs_device *btrfs_alloc_device(struct btrfs_fs_info *fs_info,