btrfs_subvolume_reserve_metadata
ret = btrfs_subvolume_reserve_metadata(root, &block_rsv, 5, true);
ret = btrfs_subvolume_reserve_metadata(root, &block_rsv,
ret = btrfs_subvolume_reserve_metadata(BTRFS_I(dir)->root, block_rsv,
int btrfs_subvolume_reserve_metadata(struct btrfs_root *root,