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I recently started using liburing and tried to write some demos. I met trouble when tried to write something into the disk.

Here is my code, the error check has been removed.

#include "liburing.h"

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/uio.h>
#include <unistd.h>

int main() {
  struct io_uring ring;
  struct iovec *iovecs;
  struct io_uring_sqe *sqe;
  struct io_uring_cqe *cqe;
  int fd;
  void *buf;

  int ret = io_uring_queue_init(4, &ring, 0);

  fd = open("./tmp_file", O_WRONLY | O_TRUNC | O_CREAT, 0644);
  ret = ftruncate(fd, 4096);

  sqe = io_uring_get_sqe(&ring);

  posix_memalign(&buf, 4096, 4096);
  memset(buf, 0x2, 4096);

  sqe = io_uring_get_sqe(&ring);
  io_uring_prep_write(sqe, fd, buf, 4096, 0);
  ret = io_uring_submit(&ring);

  ret = io_uring_wait_cqe(&ring, &cqe);
  printf("cqe->res: %d\n", cqe->res);
  io_uring_cqe_seen(&ring, cqe);

  io_uring_queue_exit(&ring);
  close(fd);
  return 0;
}

cqe->res always return 0. I have no clues to continue the search.

My kernel version is linux 5.4.56, and the liburing version is liburing-2.1. I compiled my demo with GCC 830.

I also tried other existing examples, compiled them from the source, they work just fine.

Any help is appreciated, thank you very much.

Amor Fati
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1 Answers1

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You call 'io_uring_get_sqe' twice. Try to remove one of them.

I did it and run your code. It's working!

klsirop
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