oracular (3) io_uring_prep_msg_ring_fd_alloc.3.gz

NAME

       io_uring_prep_msg_ring_fd - send a direct descriptor to another ring

SYNOPSIS

       #include <liburing.h>

       void io_uring_prep_msg_ring_fd(struct io_uring_sqe *sqe,
                               int fd,
                               int source_fd,
                               int target_fd,
                               __u64 data,
                               unsigned int flags);

       void io_uring_prep_msg_ring_fd_alloc(struct io_uring_sqe *sqe,
                               int fd,
                               int source_fd,
                               __u64 data,
                               unsigned int flags);

DESCRIPTION

       io_uring_prep_msg_ring_fd(3)  prepares  an  SQE  to  send  a  direct file descriptor to another ring. The
       submission queue entry sqe is setup to use the file descriptor fd, which must identify a target  io_uring
       context, to send the locally registered file descriptor with value source_fd to the destination ring into
       index target_fd and passing data as the user data in the target CQE with the request modifier  flags  set
       by flags.  Currently there are no valid flag modifiers, this field must contain 0.

       io_uring_prep_msg_ring_fd_alloc(3)  is  similar  to  io_uring_prep_msg_ring_fd(3),  but doesn't specify a
       target index for the direct descriptor. Instead, this index is allocated in the target ring and  returned
       in the CQE res field.

RETURN VALUE

       None

ERRORS

       These are the errors that are reported in the CQE res field.

       -ENOMEM
              The kernel was unable to allocate memory for the request.

       -EINVAL
              One of the fields set in the SQE was invalid.

       -EINVAL
              Target ring is identical to the source ring.

       -EBADFD
              The  descriptor  passed  in  fd does not refer to an io_uring file descriptor, or the ring is in a
              disabled state.

       -EOVERFLOW
              The kernel was unable to fill a CQE on the target ring. This can happen if the target CQ  ring  is
              in an overflow state and the kernel wasn't able to allocate memory for a new CQE entry.

       -ENFILE
              The  direct descriptor table in the target ring was full, no new descriptors could be successfully
              allocated.