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 DAA47C433EF for ; Mon, 6 Sep 2021 08:26:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C4B8A60555 for ; Mon, 6 Sep 2021 08:26:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240765AbhIFI1m (ORCPT ); Mon, 6 Sep 2021 04:27:42 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:38506 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241063AbhIFI1j (ORCPT ); Mon, 6 Sep 2021 04:27:39 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R281e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01424;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0UnOxwuy_1630916793; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UnOxwuy_1630916793) by smtp.aliyun-inc.com(127.0.0.1); Mon, 06 Sep 2021 16:26:33 +0800 Subject: Re: [PATCH 6/6] io_uring: enable multishot mode for accept 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> From: Hao Xu Message-ID: Date: Mon, 6 Sep 2021 16:26:32 +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 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 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. >