From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 060D6C433EF for ; Wed, 11 May 2022 13:32:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242171AbiEKNcY (ORCPT ); Wed, 11 May 2022 09:32:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232658AbiEKNcX (ORCPT ); Wed, 11 May 2022 09:32:23 -0400 Received: from out30-56.freemail.mail.aliyun.com (out30-56.freemail.mail.aliyun.com [115.124.30.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B89C162204; Wed, 11 May 2022 06:32:17 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01424;MF=tonylu@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VCwIlBX_1652275933; Received: from localhost(mailfrom:tonylu@linux.alibaba.com fp:SMTPD_---0VCwIlBX_1652275933) by smtp.aliyun-inc.com(127.0.0.1); Wed, 11 May 2022 21:32:14 +0800 Date: Wed, 11 May 2022 21:32:13 +0800 From: Tony Lu To: Guangguan Wang Cc: kgraul@linux.ibm.com, davem@davemloft.net, kuba@kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net 2/2] net/smc: align the connect behaviour with TCP Message-ID: Reply-To: Tony Lu References: <20220509115837.94911-1-guangguan.wang@linux.alibaba.com> <20220509115837.94911-3-guangguan.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, May 10, 2022 at 08:58:38PM +0800, Guangguan Wang wrote: > > > On 2022/5/10 17:30, Tony Lu wrote: > > On Mon, May 09, 2022 at 07:58:37PM +0800, Guangguan Wang wrote: > >> Connect with O_NONBLOCK will not be completed immediately > >> and returns -EINPROGRESS. It is possible to use selector/poll > >> for completion by selecting the socket for writing. After select > >> indicates writability, a second connect function call will return > >> 0 to indicate connected successfully as TCP does, but smc returns > > > > If the connection is established successfully, the following up call of > > connect() returns -EISCONN (SS_CONNECTED), which is expected and SMC > > does it, same as TCP. > > > > In case of misunderstanding, could you append more detailed information? > > > > Thanks, > > Tony Lu > > > > io_uring uses nonblocking connect as follow steps: > 1) call connect with nonblocking > 2) wait for selector/poll to indicate writability > 3) call connect to confirm connection's state > > In the third step, tcp changes the socket state from SS_CONNECTING to > SS_CONNECTED and returns 0 if the connection is established successfully, > but smc returns -EISCONN. Based on the steps you list, I am wondering if it is finished in the step #1, the call of connect() in step #3 would return -EISCONN. Should we check 0 and -EISCONN in step #3? To fix this issue, I think we should be careful about adding and handling sock state, maybe we could push it to net-next and take advantage of sock state. And I will test this patch later in our test cases. Thanks, Tony Lu