---
name: "io_uring_prep_fadvise"
section: "3"
platform: "linux"
package: "liburing"
version: "2.15-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/io_uring_prep_fadvise"
---

# io\_uring\_prep\_fadvise(3)

prepare a fadvise request

## NAME

io\_uring\_prep\_fadvise - prepare a fadvise request

## SYNOPSIS

```
#include <fcntl.h>
#include <liburing.h>
```

**void io\_uring\_prep\_fadvise(struct io\_uring\_sqe \****sqe***,**                            **int** *fd***,**                            **\_\_u64** *offset***,**                            **\_\_u32** *len***,**                            **int** *advice***);** **void io\_uring\_prep\_fadvise64(struct io\_uring\_sqe \****sqe***,**                              **int** *fd***,**                              **\_\_u64** *offset***,**                              **off\_t** *len***,**                              **int** *advice***);**

## DESCRIPTION

The [**io\_uring\_prep\_fadvise**(3)](/io_uring_prep_fadvise/3.md) function prepares an fadvise request. The submission queue entry *sqe* is setup to use the file descriptor pointed to by *fd* to start an fadvise operation at *offset* and of *len* length in bytes, giving it the advise located in *advice*.

The [**io\_uring\_prep\_fadvise64**(3)](/io_uring_prep_fadvise64/3.md) function works like [**io\_uring\_prep\_fadvise**(3)](/io_uring_prep_fadvise/3.md) except that it takes a 64-bit length rather than just a 32-bit one. Older kernels may not support the 64-bit length variant. If this variant is attempted used on a kernel that doesn't support 64-bit lengths, then the request will get errored with **-EINVAL** in the results field of the CQE.

This function prepares an async [**posix\_fadvise**(2)](/posix_fadvise/2.md) 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**(3)](/io_uring_get_sqe/3.md), [**io\_uring\_submit**(3)](/io_uring_submit/3.md), [**io\_uring\_register**(2)](/io_uring_register/2.md), [**posix\_fadvise**(2)](/posix_fadvise/2.md)