---
name: "io_uring_prep_files_update"
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_files_update"
---

# io\_uring\_prep\_files\_update(3)

prepare a registered file update request

## NAME

io\_uring\_prep\_files\_update - prepare a registered file update request

## SYNOPSIS

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

**void io\_uring\_prep\_files\_update(struct io\_uring\_sqe \****sqe***,**                                 **int \****fds***,**                                 **unsigned** *nr\_fds***,**                                 **int** *offset***);**

## DESCRIPTION

The [**io\_uring\_prep\_files\_update**(3)](/io_uring_prep_files_update/3.md) function prepares a request for updating a number of previously registered file descriptors. The submission queue entry *sqe* is setup to use the file descriptor array pointed to by *fds* and of *nr\_fds* in length to update that amount of previously registered files starting at offset *offset*.

Once a previously registered file is updated with a new one, the existing entry is updated and then removed from the table. This operation is equivalent to first unregistering that entry and then inserting a new one, just bundled into one combined operation.

If *offset* is specified as IORING\_FILE\_INDEX\_ALLOC, io\_uring will allocate free direct descriptors instead of having the application to pass, and store allocated direct descriptors into *fds* array, *cqe-\>res* will return the number of direct descriptors allocated.

## RETURN VALUE

None

## ERRORS

These are the errors that are reported in the CQE *res* field. On success, *res* will contain the number of successfully updated file descriptors. On error, the following errors can occur.

- **-ENOMEM**

  The kernel was unable to allocate memory for the request.

- **-EINVAL**

  One of the fields set in the SQE was invalid.

- **-EFAULT**

  The kernel was unable to copy in the memory pointed to by *fds*.

- **-EBADF**

  On of the descriptors located in *fds* didn't refer to a valid file descriptor, or one of the file descriptors in the array referred to an io\_uring instance.

- **-EOVERFLOW**

  The product of *offset* and *nr\_fds* exceed the valid amount or overflowed.

## NOTES

As with any request that passes in data in a struct, that data must remain valid until the request has been successfully submitted. It need not remain valid until completion. Once a request has been submitted, the in-kernel state is stable. Very early kernels (5.4 and earlier) required state to be stable until the completion occurred. Applications can test for this behavior by inspecting the **IORING\_FEAT\_SUBMIT\_STABLE** flag passed back from [**io\_uring\_queue\_init\_params**(3)](/io_uring_queue_init_params/3.md).

## 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)