Method read

src/blk/kernel/KernelDevice.cc:1428–1474

}

int KernelDevice::read(uint64_t off, uint64_t len, bufferlist *pbl,
		      IOContext *ioc,
		      bool buffered)
{
  dout(5) << __func__ << " 0x" << std::hex << off << "~" << len << std::dec
	  << " " << buffermode(buffered)
	  << dendl;
  ceph_assert(is_valid_io(off, len));

  _aio_log_start(ioc, off, len);

  auto start1 = mono_clock::now();

  auto p = ceph::buffer::ptr_node::create(create_custom_aligned(len, ioc));
  int r = ::pread(choose_fd(buffered,  WRITE_LIFE_NOT_SET),
		  p->c_str(), len, off);
  auto age = cct->_conf->bdev_debug_aio_log_age;
  if (mono_clock::now() - start1 >= make_timespan(age)) {
    derr << __func__ << " stalled read "
         << " 0x" << std::hex << off << "~" << len << std::dec
         << " " << buffermode(buffered)
	 << " since " << start1 << ", timeout is "
	 << age
	 << "s" << dendl;
    add_stalled_read_event();
  }
  if (r < 0) {
    if (ioc->allow_eio && is_expected_ioerr(-errno)) {
      r = -EIO;
    } else {
      r = -errno;
    }
    derr << __func__ << " 0x" << std::hex << off << "~" << std::left
         << std::dec << " error: " << cpp_strerror(r) << dendl;
    goto out;
  }
  ceph_assert((uint64_t)r == len);
  pbl->push_back(std::move(p));

  dout(40) << "data:\n"; 
  pbl->hexdump(*_dout);
  *_dout << dendl;

 out:
  _aio_log_finish(ioc, off, len);
  return r < 0 ? r : 0;
}

int KernelDevice::aio_read(
  uint64_t off,