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=-19.1 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 D3CB4C433EF for ; Sun, 5 Sep 2021 07:29:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A622560F3A for ; Sun, 5 Sep 2021 07:29:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237592AbhIEHap (ORCPT ); Sun, 5 Sep 2021 03:30:45 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:49650 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237457AbhIEHac (ORCPT ); Sun, 5 Sep 2021 03:30:32 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04395;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0UnGZUhL_1630826967; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UnGZUhL_1630826967) by smtp.aliyun-inc.com(127.0.0.1); Sun, 05 Sep 2021 15:29:28 +0800 Subject: Re: [PATCH 6/6] io_uring: enable multishot mode for accept To: Pavel Begunkov , Jens Axboe 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: <6fad63c4-8251-3cf7-af8e-16e6b94bbf7f@linux.alibaba.com> Date: Sun, 5 Sep 2021 15:29:27 +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: <701e50f5-2444-5b56-749b-1c1affc26ce9@gmail.com> 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 2021/9/5 上午6:46, Pavel Begunkov 写道: > 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. I think leverage the highest bit of ioprio may be a good idea? > >> Probably best to solve that issue in include/linux/net.h, ala: >> >> /* Flags for socket, socketpair, accept4 */ >> #define SOCK_CLOEXEC O_CLOEXEC >> #ifndef SOCK_NONBLOCK >> #define SOCK_NONBLOCK O_NONBLOCK >> #endif >> >> /* >> * Only used for io_uring accept4, and deliberately chosen to overlap >> * with the O_* file bits for read/write mode so we won't risk overlap >> * other flags added for socket/socketpair/accept4 use in the future. >> */ >> #define SOCK_URING_MULTISHOT 00000001 >> >> which should be OK, as these overlap with the O_* filespace and the >> read/write bits are at the start of that space. >> >> Should be done as a prep patch and sent out to netdev as well, so we can >> get their sign-off on this "hack". If we can get that done, then we have >> our flag and we can just stuff it in accept->flags as long as we clear >> it before calling into accept from io_uring. >> >