NAME

       io_uring_register_buffers - register buffers for fixed buffer operations

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

       The  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) function behaves the same as 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) 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).

       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)  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

       On        success        io_uring_register_buffers(3),        io_uring_register_buffers_tags(3)       and
       io_uring_register_buffers_sparse(3) return 0.  io_uring_register_buffers_update_tag(3) return  number  of
       buffers updated.  On failure they return -errno.

SEE ALSO

       io_uring_register(2),   io_uring_get_sqe(3),  io_uring_unregister_buffers(3),  io_uring_clone_buffers(3),
       io_uring_register_buf_ring(3), io_uring_prep_read_fixed(3), io_uring_prep_write_fixed(3)

liburing-2.1                                    November 15, 2021                   io_uring_register_buffers(3)