pkg/fileutil/preallocate.go
func Preallocate(f *os.File, sizeInBytes int64, extendFile bool) error {
	if sizeInBytes == 0 {
		// fallocate will return EINVAL if length is 0; skip
		return nil
	}
	if extendFile {
		return preallocExtend(f, sizeInBytes)
	}
	return preallocFixed(f, sizeInBytes)
}
func Preallocate(f *os.File, sizeInBytes int64, extendFile bool) error {
	if sizeInBytes == 0 {
		// fallocate will return EINVAL if length is 0; skip
		return nil
	}
	if extendFile {
		return preallocExtend(f, sizeInBytes)
	}
	return preallocFixed(f, sizeInBytes)
}
// Preallocate tries to allocate the space for given
// file. This operation is only supported on linux by a
// few filesystems (btrfs, ext4, etc.).
// If the operation is unsupported, no error will be returned.
// Otherwise, the error encountered will be returned.