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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | COLOPHON |
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io_uring_register_region(3) liburing Manual io_uring_register_region(3)
io_uring_register_region - register a memory region
#include <liburing.h>
int io_uring_register_region(struct io_uring *ring,
struct io_uring_mem_region_reg *reg);
The io_uring_register_region(3) function registers a memory region
to io_uring. Upon successful completion, the memory region may
then be used, for example, to pass waiting parameters to the
io_uring_enter(2) system call in a more efficient manner as it
avoids copying wait related data for each wait event. The ring
argument should point to the ring in question, and the reg
argument should be a pointer to a struct io_uring_mem_region_reg .
The reg argument must be filled in with the appropriate
information. It looks as follows:
struct io_uring_mem_region_reg {
__u64 region_uptr;
__u64 flags;
__u64 __resv[2];
};
The region_uptr field must contain a pointer to an appropriately
filled struct io_uring_region_desc.
The flags field must contain a bitmask of the following values:
IORING_MEM_REGION_REG_WAIT_ARG
allows use of the region to pass waiting parameters to the
io_uring_enter(2) system call. If set, the registration is
only allowed while the ring is in a disabled mode. See
IORING_SETUP_R_DISABLED.
The __resv fields must be filled with zeroes.
struct io_uring_region_desc is defined as following:
struct io_uring_region_desc {
__u64 user_addr;
__u64 size;
__u32 flags;
__u32 id;
__u64 mmap_offset;
__u64 __resv[4];
};
The user_addr field must contain a pointer to the memory the user
wants to register. It's valid only if IORING_MEM_REGION_TYPE_USER
is set, and should be zero otherwise.
The size field should contain the size of the region.
The flags field must contain a bitmask of the following values:
IORING_MEM_REGION_TYPE_USER
tells the kernel to use memory specified by the user_addr
field. If not set, the kernel will allocate memory for the
region, which can then be mapped into the user space.
On successful registration of a region with kernel provided
memory, the mmap_offset field will contain an offset that can be
passed to the mmap(2) system call to map the region into the user
space.
The id field is reserved and must be set to zero.
The __resv fields must be filled with zeroes.
Available since kernel 6.13.
On success io_uring_register_region(3) returns 0. On failure it
returns -errno.
This page is part of the liburing (A library for io_uring)
project. Information about the project can be found at
⟨https://github.com/axboe/liburing⟩. If you have a bug report for
this manual page, send it to io-uring@vger.kernel.org. This page
was obtained from the project's upstream Git repository
⟨https://github.com/axboe/liburing⟩ on 2026-01-16. (At that time,
the date of the most recent commit that was found in the
repository was 2026-01-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
liburing-2.14 Jan 13, 2026 io_uring_register_region(3)
Pages that refer to this page: io_uring_register_region(3), io_uring_submit_and_wait_reg(3)
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HTML rendering created 2026-01-16 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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