io\_uring\_register\_buffers(3) liburing Manual io\_uring\_register\_buffers(3)

# [NAME](#NAME)

io\_uring\_register\_buffers - register buffers for fixed buffer operations

# [SYNOPSIS](#SYNOPSIS)

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

```
int io_uring_register_buffers(struct io_uring *ring,
                              const struct iovec *iovecs,
                              unsigned nr_iovecs);
```

```
int io_uring_register_buffers_tags(struct io_uring *ring,
                                   const struct iovec *iovecs,
                                   const __u64 *tags,
                                   unsigned nr);
```

```
int io_uring_register_buffers_sparse(struct io_uring *ring,
                                     unsigned nr_iovecs);
```

```
int io_uring_register_buffers_update_tag(struct io_uring *ring,
                                         unsigned off,
                                         const struct iovec *iovecs,
                                         const __u64 *tags,
                                         unsigned nr);
```

# [DESCRIPTION](#DESCRIPTION)

The [**io\_uring\_register\_buffers**(3)](/man/os/liburing/io_uring_register_buffers.3) function registers *nr\_iovecs* number of buffers defined by the array *iovecs* belonging to the *ring*.

The [**io\_uring\_register\_buffers\_tags**(3)](/man/os/liburing/io_uring_register_buffers_tags.3) function behaves the same as [**io\_uring\_register\_buffers**(3)](/man/os/liburing/io_uring_register_buffers.3) function but additionally takes *tags* parameter. See **IORING\_REGISTER\_BUFFERS2** for the resource tagging description.

The [**io\_uring\_register\_buffers\_sparse**(3)](/man/os/liburing/io_uring_register_buffers_sparse.3) function registers *nr\_iovecs* empty buffers belonging to the *ring*. These buffers must be updated before use, using eg [**io\_uring\_register\_buffers\_update\_tag**(3)](/man/os/liburing/io_uring_register_buffers_update_tag.3).

After the caller has registered the buffers, they can be used with one of the fixed buffers functions.

Registered buffers is an optimization that is useful in conjunction with **O\_DIRECT** reads and writes, where it maps the specified range into the kernel once when the buffer is registered rather than doing a map and unmap for each IO every time IO is performed to that region. Additionally, it also avoids manipulating the page reference counts for each IO.

The [**io\_uring\_register\_buffers\_update\_tag**(3)](/man/os/liburing/io_uring_register_buffers_update_tag.3) function updates registered buffers with new ones, either turning a sparse entry into a real one, or replacing an existing entry. The *off* is offset on which to start the update *nr* number of buffers defined by the array *iovecs* belonging to the *ring*. The *tags* points to an array of tags. See **IORING\_REGISTER\_BUFFERS2** for the resource tagging description.

# [RETURN VALUE](#RETURN_VALUE)

On success [**io\_uring\_register\_buffers**(3)](/man/os/liburing/io_uring_register_buffers.3), [**io\_uring\_register\_buffers\_tags**(3)](/man/os/liburing/io_uring_register_buffers_tags.3) and [**io\_uring\_register\_buffers\_sparse**(3)](/man/os/liburing/io_uring_register_buffers_sparse.3) return 0. [**io\_uring\_register\_buffers\_update\_tag**(3)](/man/os/liburing/io_uring_register_buffers_update_tag.3) return number of buffers updated. On failure they return **-errno**.

# [SEE ALSO](#SEE_ALSO)

[**io\_uring\_register**(2)](/man/os/liburing/io_uring_register.2), [**io\_uring\_get\_sqe**(3)](/man/os/liburing/io_uring_get_sqe.3), [**io\_uring\_unregister\_buffers**(3)](/man/os/liburing/io_uring_unregister_buffers.3), [**io\_uring\_clone\_buffers**(3)](/man/os/liburing/io_uring_clone_buffers.3), [**io\_uring\_register\_buf\_ring**(3)](/man/os/liburing/io_uring_register_buf_ring.3), [**io\_uring\_prep\_read\_fixed**(3)](/man/os/liburing/io_uring_prep_read_fixed.3), [**io\_uring\_prep\_write\_fixed**(3)](/man/os/liburing/io_uring_prep_write_fixed.3)

November 15, 2021 liburing-2.1

---

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