Hi Stefan and Jens, Thanks for the help. BTW, the issue is observed when I write ublk-nbd: https://github.com/ming1/ubdsrv/commits/nbd and it isn't completed yet(multiple send sqe chains not serialized yet), the issue is triggered when writing big chunk data to ublk-nbd. On Wed, Jan 11, 2023 at 05:32:00PM +0100, Stefan Metzmacher wrote: > 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. Turns out there is another application bug in which recv sqe may cut in the send sqe chain. After the issue is fixed, if MSG_WAITALL is set, short send can't be observed any more. But if MSG_WAITALL isn't set, short send can be observed and the send io chain still won't be terminated. So if MSG_WAITALL is set, will io_uring be responsible for retry in case of short send, and application needn't to take care of it? > > For recv and recvmsg MSG_WAITALL also fails the link for MSG_TRUNC and MSG_CTRUNC. OK, thanks for the sharing of recvmsg MSG_WAITALL. Thanks, Ming
