Re: Chaining accept+read

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

On 9/28/22 10:50, Ben Noordhuis wrote:
> I'm trying to chain accept+read but it's not working.
> 
> My code looks like this:
> 
>      *sqe1 = (struct io_uring_sqe){
>        .opcode     = IORING_OP_ACCEPT,
>        .flags      = IOSQE_IO_LINK,
>        .fd         = listenfd,
>        .file_index = 42, // or 42+1
>      };
>      *sqe2 = (struct io_uring_sqe){
>        .opcode     = IORING_OP_READ,
>        .flags      = IOSQE_FIXED_FILE,
>        .addr       = (u64) buf,
>        .len        = len,
>        .fd         = 42,
>      };
>      submit();
> 
> Both ops fail immediately; accept with -ECANCELED, read with -EBADF,
> presumably because fixed fd 42 doesn't exist at the time of submission.
> 
> Would it be possible to support this pattern in io_uring or are there
> reasons for why things are the way they are?

It should already be supported. And errors look a bit odd, I'd rather
expect -EBADF or some other for accept and -ECANCELED for the read.
Do you have a test program / reporoducer? Hopefully in C.

-- 
Pavel Begunkov