PosixAIO：aio_error返回38（未实现）但errno为0（成功）

Question

我的代码在本机 Linux 系统上运行得很好，但是当我在 WSL 上运行它时，似乎出了问题。

这是我发送 AsyncWrites 的方式：

Status PosixAIOEngine::AsyncWrite(int fd, uint64_t offset, const char* buffer, uint64_t size,
                                  char** cb) {
  if (requests_.size() >= io_depth_) {
    LOG(ERROR, "io depth full, please try again later, cur: {}", io_depth_);
    return Status::Busy();
  }

  requests_.push_back({.aio_req_ = {}, .type_ = kAsyncWrite});
  auto& request = requests_.back();
  memset(&request.aio_req_, 0, sizeof(struct aiocb));
  request.aio_req_.aio_offset = (off_t)offset;
  request.aio_req_.aio_buf = (void*)buffer;
  request.aio_req_.aio_nbytes = size;
  request.aio_req_.aio_fildes = fd;

  int ret = aio_write(&request.aio_req_);
  if (ret == -1) {
    auto msg = "aio_write failed, err msg: " + std::string(strerror(errno));
    LOG(ERROR, msg);
    requests_.pop_back();
    return Status::IOError(msg);
  }

  return Status::OK();
}

发出几个写请求后，我在这里轮询结果：

uint32_t PosixAIOEngine::Poll() {
  uint32_t cnt = 0;
  auto it = requests_.begin();
  while (it != requests_.end()) {
    auto& req = *it;
    int err_value = aio_error(&req.aio_req_);

    // If the request was canceld, we remove & skip it.
    if (err_value == ECANCELED) {
      it = requests_.erase(it);
      continue;
    }

    // If the request is not yet completed, we skip it.
    if (err_value == EINPROGRESS) {
      ++it;
      continue;
    }

    // If the request has an error.
    if (err_value != 0) { <------------------- ERROR here <<<<<<<<<<<<<<<<<<
      LOG(ERROR, "I/O failed, aio_error: {}, errmsg: {}, offset: {}", err_value, strerror(errno),
          req.aio_req_.aio_offset);
      it = requests_.erase(it);
      continue;
    }

    // If there's no operation error occurs, we should check the return value.
    int ret_value = aio_return(&req.aio_req_);
    if (ret_value == -1) {
      LOG(ERROR, "I/O failed, aio_return: {}, errmsg: {}, offset: {}", ret_value, strerror(errno),
          req.aio_req_.aio_offset);
      it = requests_.erase(it);
      continue;
    }

    // Otherwise, the operation success
    it = requests_.erase(it);
    cnt++;
  }

我首先检查

aio_error

以确保请求已正确发送出去，但它的返回值是38，这意味着

Not Implemented

。我想errno也会改变，但结果errno仍然是0，这意味着成功。

问题：

1. 为什么aio_error返回非零值后errno没有改变。
2. 我应该如何修复我的演示代码？

根据这个API的描述：，好像errno的值应该是一样的吧？或者我误解了描述...（不是母语人士）

A positive error number, if the asynchronous I/O operation
              failed.  This is the same value that would have been
              stored in the errno variable in the case of a synchronous
              read(2), write(2), fsync(2), or fdatasync(2) call.

Answer 1

好的，解决方案在这里：

事实证明，WSL1.0 无法正确处理异步

aio

（在

aio.h

下），所以我将其升级到 WSL2.0，完美运行。