io_uring nvme passthru, see https://jianyue.tech/posts/io_uring-passthrough/

io_uring_nvme_passthru.c

#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/nvme_ioctl.h>
#include <liburing.h>

int iouring_setup(unsigned entries, struct io_uring *ring)
{
    return io_uring_queue_init(entries, ring, IORING_SETUP_SQE128 |
                                              IORING_SETUP_CQE32);
}

void iouring_exit(struct io_uring *ring)
{
    io_uring_queue_exit(ring);
}

int iouring_passthru_enqueue(struct io_uring *ring, int fd,
                             const struct nvme_uring_cmd *cmd)
{
    // https://github.com/joshkan/fio/blob/big-cqe-pt.v4/engines/io_uring.c
    struct io_uring_sqe *sqe = io_uring_get_sqe(ring);
    if (!sqe) {
        printf("Failed to get io_uring sqe\n");
        return -1;
    }
    // fd = open('/dev/ng0n1')
    // see https://lpc.events/event/11/contributions/989/attachments/747/1723/lpc-2021-building-a-fast-passthru.pdf
    sqe->fd = fd;
    sqe->opcode = IORING_OP_URING_CMD;
    sqe->cmd_op = NVME_URING_CMD_IO;  // see linux/nvme_ioctl.h
    memcpy(sqe->cmd, cmd, sizeof(struct nvme_uring_cmd));
    return 0;
}

int iouring_submit(struct io_uring *ring)
{
    int nr = io_uring_submit(ring);
    if (nr < 0) {
        perror("io_uring_submit");
        return -1;
    }
    return nr;
}

int iouring_wait_nr(struct io_uring *ring, int nr)
{
    struct io_uring_cqe *cqes = NULL;
    if (io_uring_wait_cqe_nr(ring, &cqes, nr) < 0) {
        perror("io_uring_wait_cqes");
        return -1;
    }
    for (int i = 0; i < nr; i++) {
        struct io_uring_cqe *cqe = &cqes[i];
        int err = cqe->big_cqe[0] || cqe->res;
        if (err) {
            fprintf(stderr, "io_uring_wait_cqe_nr: %d, %s\n", err, strerror(-err));
            return -1;
        }
    }
    return nr;
}