But: " A filesystem may place limitations on the granularity of the operation, in order to ensure efficient implementation. Typically, offset and

But: " A filesystem may place limitations on the granularity of the operation, in order to ensure efficient implementation. Typically, offset and len must be a multiple of the filesystem logical block size, which varies according to the filesystem type and configuration. If a filesystem has such a requirement, fallocate() fails with the error EINVAL if this requirement is violated." Seems it's limited.