Re: [PATCH 1/1] io_uring/net: send retry for zerocopy

[Jens Axboe <axboe@kernel.dk>]

On 8/14/22 8:11 AM, Stefan Metzmacher wrote:
> Hi Jens,
> 
>>>> io_uring handles short sends/recvs for stream sockets when MSG_WAITALL
>>>> is set, however new zerocopy send is inconsistent in this regard, which
>>>> might be confusing. Handle short sends.
>>>>
>>>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>>>> ---
>>>>    io_uring/net.c | 20 +++++++++++++++++---
>>>>    1 file changed, 17 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/io_uring/net.c b/io_uring/net.c
>>>> index 32fc3da04e41..f9f080b3cc1e 100644
>>>> --- a/io_uring/net.c
>>>> +++ b/io_uring/net.c
>>>> @@ -70,6 +70,7 @@ struct io_sendzc {
>>>>        unsigned            flags;
>>>>        unsigned            addr_len;
>>>>        void __user            *addr;
>>>> +    size_t                done_io;
>>>>    };
>>>>      #define IO_APOLL_MULTI_POLLED (REQ_F_APOLL_MULTISHOT | REQ_F_POLLED)
>>>> @@ -878,6 +879,7 @@ int io_sendzc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>>          zc->addr = u64_to_user_ptr(READ_ONCE(sqe->addr2));
>>>>        zc->addr_len = READ_ONCE(sqe->addr_len);
>>>> +    zc->done_io = 0;
>>>>      #ifdef CONFIG_COMPAT
>>>>        if (req->ctx->compat)
>>>> @@ -1012,11 +1014,23 @@ int io_sendzc(struct io_kiocb *req, unsigned int issue_flags)
>>>>        if (unlikely(ret < min_ret)) {
>>>>            if (ret == -EAGAIN && (issue_flags & IO_URING_F_NONBLOCK))
>>>>                return -EAGAIN;
>>>> -        return ret == -ERESTARTSYS ? -EINTR : ret;
>>>> +        if (ret > 0 && io_net_retry(sock, msg.msg_flags)) {
>>>> +            zc->len -= ret;
>>>> +            zc->buf += ret;
>>>> +            zc->done_io += ret;
>>>> +            req->flags |= REQ_F_PARTIAL_IO;
>>>
>>> Don't we need a prep_async function and/or something like
>>> io_setup_async_msg() here to handle address?
>>
>> I don't think so, it's a non-vectored interface, so all the state is
>> already in io_sendzc.
> 
> This has support for sockaddr address compared to io_send(),
> if the caller need to keep io_sendzc->addr valid until the qce arrived,
> then we need to clearly document that, as that doesn't match the common practice
> of other opcodes. Currently everything but data buffers can go after the sqe is
> submitted.

Good point, it's not just the 'from' address. Pavel?

-- 
Jens Axboe