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Date:   Wed, 11 Jan 2023 17:32:00 +0100
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Subject: Re: IOSQE_IO_LINK vs. short send of SOCK_STREAM
Content-Language: en-US
To:     Ming Lei <ming.lei@redhat.com>, io-uring@vger.kernel.org,
        Pavel Begunkov <asml.silence@gmail.com>,
        Jens Axboe <axboe@kernel.dk>
Cc:     David Ahern <dsahern@gmail.com>
References: <Y77VIB1s6LurAvBd@T590>
From:   Stefan Metzmacher <metze@samba.org>
In-Reply-To: <Y77VIB1s6LurAvBd@T590>
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Hi Ming,

> Per my understanding, a short send on SOCK_STREAM should terminate the
> remainder of the SQE chain built by IOSQE_IO_LINK.
> 
> But from my observation, this point isn't true when using io_sendmsg or
> io_sendmsg_zc on TCP socket, and the other remainder of the chain still
> can be completed after one short send is found. MSG_WAITALL is off.

This is due to legacy reasons, you need pass MSG_WAITALL explicitly
in order to a retry or an error on a short write...
It should work for send, sendmsg, sendmsg_zc, recv and recvmsg.

For recv and recvmsg MSG_WAITALL also fails the link for MSG_TRUNC and MSG_CTRUNC.

metze