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Sun, 05 Sep 2021 01:27:50 -0700 (PDT) To: Hao Xu , 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> <3cdcd28b-4723-32f8-5a0f-59fab8f4af27@gmail.com> <1542ac87-c518-3aa4-55ca-061f2761a1db@linux.alibaba.com> From: Pavel Begunkov Subject: Re: [PATCH 6/6] io_uring: enable multishot mode for accept Message-ID: <26a08d43-c3bf-fa24-3830-dd3f8e626f80@gmail.com> Date: Sun, 5 Sep 2021 09:27:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <1542ac87-c518-3aa4-55ca-061f2761a1db@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 9/5/21 7:25 AM, Hao Xu wrote: > 在 2021/9/5 上午6:43, Pavel Begunkov 写道: >> On 9/3/21 12:00 PM, 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; >> >> Why REQ_F_FORCE_ASYNC is not allowed? It doesn't sound like there >> should be any problem, would just eventually go looping >> poll_wait + tw > Hmm..The arm_poll facility is only on the io_submit_sqes() path. If > FORCE_ASYNC is set, the req goes to io_wq_submit_work-->io_issue_sqe. > Moreover, I guess theoretically poll based retry and async iowq are > two ways for users to handle their sqes, it may not be sane to go to > poll based retry path if a user already forcely choose iowq as their > prefer way. The flag is just a hint, there are already plenty of ways to trick requests into tw. Forbidding it would be inconsistent. >>> + >>>       accept->file_slot = READ_ONCE(sqe->file_index); >>>       if (accept->file_slot && ((req->open.how.flags & O_CLOEXEC) || >>> -                  (accept->flags & SOCK_CLOEXEC))) >>> +                  (accept->flags & SOCK_CLOEXEC) || is_multishot)) >>>           return -EINVAL; >>> -    if (accept->flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK)) >>> +    if (accept->flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK | IORING_ACCEPT_MULTISHOT)) >>>           return -EINVAL; >>>       if (SOCK_NONBLOCK != O_NONBLOCK && (accept->flags & SOCK_NONBLOCK)) >>>           accept->flags = (accept->flags & ~SOCK_NONBLOCK) | O_NONBLOCK; >>> +    if (is_multishot) { >>> +        req->flags |= REQ_F_APOLL_MULTISHOT; >>> +        accept->flags &= ~IORING_ACCEPT_MULTISHOT; >>> +    } >>> + >>>       return 0; >>>   } >>>   >> > -- Pavel Begunkov