io\_uring\_prep\_files\_update(3) liburing Manual io\_uring\_prep\_files\_update(3)

# [NAME](#NAME)

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

# [SYNOPSIS](#SYNOPSIS)

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

```
void io_uring_prep_files_update(struct io_uring_sqe *sqe,
                                int *fds,
                                unsigned nr_fds,
                                int offset);
```

# [DESCRIPTION](#DESCRIPTION)

The [**io\_uring\_prep\_files\_update**(3)](/man/os/liburing/io_uring_prep_files_update.3) 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-&gt;res* will return the number of direct descriptors allocated.

# [RETURN VALUE](#RETURN_VALUE)

None

# [ERRORS](#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**](#ENOMEM)

The kernel was unable to allocate memory for the request.

[**-EINVAL**](#EINVAL)

One of the fields set in the SQE was invalid.

[**-EFAULT**](#EFAULT)

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

[**-EBADF**](#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**](#EOVERFLOW)

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

# [NOTES](#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)](/man/os/liburing/io_uring_queue_init_params.3).

# [SEE ALSO](#SEE_ALSO)

[**io\_uring\_get\_sqe**(3)](/man/os/liburing/io_uring_get_sqe.3), [**io\_uring\_submit**(3)](/man/os/liburing/io_uring_submit.3), [**io\_uring\_register**(2)](/man/os/liburing/io_uring_register.2)

March 13, 2022 liburing-2.2

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Document: io_uring_prep_files_update(3) from liburing 2.15-r5 (Chainguard OS)
Source: https://github.com/axboe/liburing.git