Prepare a fallocate request
# DESCRIPTION
The [io_uring_prep_fallocate] function prepares a fallocate
request. The submission queue entry *sqe* is setup to use the file
descriptor pointed to by *fd* to start a fallocate operation described
by *mode* at offset *offset* and *len* length in bytes.
This function prepares an async [fallocate](https://man7.org/linux/man-pages/man2/fallocate.2.html) request. See that man
page for details.
# RETURN VALUE
None
# ERRORS
The CQE *res* field will contain the result of the operation. See the
related man page for details on possible values. Note that where
synchronous system calls will return **-1** on failure and set *errno*
to the actual error value, io_uring never uses *errno*. Instead it
returns the negated *errno* directly in the CQE *res* field.
# SEE ALSO
[io_uring_get_sqe], [io_uring_submit], [fallocate](https://man7.org/linux/man-pages/man2/fallocate.2.html)