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 X-Spam-Level: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55336C433EF for ; Mon, 6 Sep 2021 08:28:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 311AD60F45 for ; Mon, 6 Sep 2021 08:28:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240681AbhIFI3w (ORCPT ); Mon, 6 Sep 2021 04:29:52 -0400 Received: from out30-133.freemail.mail.aliyun.com ([115.124.30.133]:33079 "EHLO out30-133.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241185AbhIFI3l (ORCPT ); Mon, 6 Sep 2021 04:29:41 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0UnOxxEu_1630916914; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UnOxxEu_1630916914) by smtp.aliyun-inc.com(127.0.0.1); Mon, 06 Sep 2021 16:28:35 +0800 Subject: Re: [PATCH 6/6] io_uring: enable multishot mode for accept From: Hao Xu To: Jens Axboe , Pavel Begunkov Cc: io-uring@vger.kernel.org, Joseph Qi References: <20210903110049.132958-1-haoxu@linux.alibaba.com> <20210903110049.132958-7-haoxu@linux.alibaba.com> <95387504-3986-77df-7cb4-d136dd4be1ec@linux.alibaba.com> <701e50f5-2444-5b56-749b-1c1affc26ce9@gmail.com> Message-ID: <84f2beb6-62bf-56d1-5a03-6a32ebf101aa@linux.alibaba.com> Date: Mon, 6 Sep 2021 16:28:34 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 在 2021/9/6 下午4:26, Hao Xu 写道: > 在 2021/9/6 上午3:44, Jens Axboe 写道: >> On 9/4/21 4:46 PM, Pavel Begunkov wrote: >>> On 9/4/21 7:40 PM, Jens Axboe wrote: >>>> On 9/4/21 9:34 AM, Hao Xu wrote: >>>>> 在 2021/9/4 上午12:29, Jens Axboe 写道: >>>>>> On 9/3/21 5:00 AM, Hao Xu wrote: >>>>>>> Update io_accept_prep() to enable multishot mode for accept >>>>>>> operation. >>>>>>> >>>>>>> Signed-off-by: Hao Xu >>>>>>> --- >>>>>>>    fs/io_uring.c | 14 ++++++++++++-- >>>>>>>    1 file changed, 12 insertions(+), 2 deletions(-) >>>>>>> >>>>>>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>>>>>> index eb81d37dce78..34612646ae3c 100644 >>>>>>> --- a/fs/io_uring.c >>>>>>> +++ b/fs/io_uring.c >>>>>>> @@ -4861,6 +4861,7 @@ static int io_recv(struct io_kiocb *req, >>>>>>> unsigned int issue_flags) >>>>>>>    static int io_accept_prep(struct io_kiocb *req, const struct >>>>>>> io_uring_sqe *sqe) >>>>>>>    { >>>>>>>        struct io_accept *accept = &req->accept; >>>>>>> +    bool is_multishot; >>>>>>>        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL)) >>>>>>>            return -EINVAL; >>>>>>> @@ -4872,14 +4873,23 @@ static int io_accept_prep(struct io_kiocb >>>>>>> *req, const struct io_uring_sqe *sqe) >>>>>>>        accept->flags = READ_ONCE(sqe->accept_flags); >>>>>>>        accept->nofile = rlimit(RLIMIT_NOFILE); >>>>>>> +    is_multishot = accept->flags & IORING_ACCEPT_MULTISHOT; >>>>>>> +    if (is_multishot && (req->flags & REQ_F_FORCE_ASYNC)) >>>>>>> +        return -EINVAL; >>>>>> >>>>>> I like the idea itself as I think it makes a lot of sense to just >>>>>> have >>>>>> an accept sitting there and generating multiple CQEs, but I'm a bit >>>>>> puzzled by how you pass it in. accept->flags is the accept4(2) flags, >>>>>> which can currently be: >>>>>> >>>>>> SOCK_NONBLOCK >>>>>> SOCK_CLOEXEC >>>>>> >>>>>> While there's not any overlap here, that is mostly by chance I >>>>>> think. A >>>>>> cleaner separation is needed here, what happens if some other >>>>>> accept4(2) >>>>>> flag is enabled and it just happens to be the same as >>>>>> IORING_ACCEPT_MULTISHOT? >>>>> Make sense, how about a new IOSQE flag, I saw not many >>>>> entries left there. >>>> >>>> Not quite sure what the best approach would be... The mshot flag only >>>> makes sense for a few request types, so a bit of a shame to have to >>>> waste an IOSQE flag on it. Especially when the flags otherwise >>>> passed in >>>> are so sparse, there's plenty of bits there. >>>> >>>> Hence while it may not be the prettiest, perhaps using accept->flags is >>>> ok and we just need some careful code to ensure that we never have any >>>> overlap. >>> >>> Or we can alias with some of the almost-never-used fields like >>> ->ioprio or ->buf_index. >> >> It's not a bad idea, as long as we can safely use flags from eg ioprio >> for cases where ioprio would never be used. In that sense it's probably >> safer than using buf_index. >> >> The alternative is, as has been brougt up before, adding a flags2 and >> reserving the last flag in ->flags to say "there are flags in flags2". > May I ask when do we have to use a bit in ->flags to do this? My ^why > understanding is just leverage a __u8 in pad2[2] in io_uring_sqe to > deliver ext_flags. >> Not exactly super pretty either, but we'll need to extend them at some >> point. >>