Re: [PATCHv4 2/5] io_uring: add support for kernel registered bvecs

[Pavel Begunkov <asml.silence@gmail.com>]

On 2/19/25 01:54, Caleb Sander Mateos wrote:
> On Tue, Feb 18, 2025 at 2:42 PM Keith Busch <kbusch@meta.com> wrote:
...
>>   int io_import_fixed(int ddir, struct iov_iter *iter,
>>                             struct io_mapped_ubuf *imu,
>>                             u64 buf_addr, size_t len)
>> @@ -874,6 +963,9 @@ int io_import_fixed(int ddir, struct iov_iter *iter,
>>          /* not inside the mapped region */
>>          if (unlikely(buf_addr < imu->ubuf || buf_end > (imu->ubuf + imu->len)))
>>                  return -EFAULT;
>> +       if ((ddir == READ && !imu->readable) ||
>> +           (ddir == WRITE && !imu->writeable))
>> +               return -EFAULT;
> 
> This could be made less branchy by storing a bitmask of allowed data
> transfer directions instead of 2 bool fields. Then this could just be:
> if (!(imu->ddirs >> ddir & 1)
>          return -EFAULT;

I'd prefer a direction mask indeed.

-- 
Pavel Begunkov