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

[Stefan Metzmacher <metze@samba.org>]

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.

metze