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Wed, 02 Sep 2020 09:03:03 -0700 (PDT) To: Jens Axboe , Norman Maurer , io-uring@vger.kernel.org Cc: Josef References: <28EF4A51-2B6D-4857-A9E8-2E28E530EFA6@googlemail.com> <05c1b12c-5fb8-c7f5-c678-65249da5a6b1@kernel.dk> <72c31af6-2c85-4105-65fb-87a860a65a78@gmail.com> <06ee57db-7fcc-140a-a9de-e6e67a68b56e@kernel.dk> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Subject: Re: IORING_OP_READ and O_NONBLOCK behaviour Message-ID: Date: Wed, 2 Sep 2020 19:00:43 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <06ee57db-7fcc-140a-a9de-e6e67a68b56e@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 02/09/2020 18:35, Jens Axboe wrote: > On 9/2/20 9:26 AM, Pavel Begunkov wrote: >> On 02/09/2020 17:45, Jens Axboe wrote: >>> On 9/2/20 4:09 AM, Norman Maurer wrote: >>>> Hi there, >>>> >>>> We are currently working on integrating io_uring into netty and found >>>> some “suprising” behaviour which seems like a bug to me. >>>> >>>> When a socket is marked as non blocking (accepted with O_NONBLOCK flag >>>> set) and there is no data to be read IORING_OP_READ should complete >>>> directly with EAGAIN or EWOULDBLOCK. This is not the case and it >>>> basically blocks forever until there is some data to read. Is this >>>> expected ? >>>> >>>> This seems to be somehow related to a bug that was fixed for >>>> IO_URING_ACCEPT with non blocking sockets: >>>> >>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.8&id=e697deed834de15d2322d0619d51893022c90ea2 >>> >>> I agree with you that this is a bug, in general it's useful (and >>> expected) that we'd return -EAGAIN for that case. I'll take a look. >>> >> >> That's I mentioned that doing retries for nonblock requests in >> io_wq_submit_work() doesn't look consistent. I think killing it >> off may help. > > Right, we should not retry those _in general_, the exception is regular > files or block devices to handle IOPOLL retry where we do need it. The > below is what I came up with for this one. Might not hurt to make this > more explicit for 5.10. Hmm, I didn't checked it, but if we > > > commit c78e0f02c3861b5b176b2f79552677b3604deb76 > Author: Jens Axboe > Date: Wed Sep 2 09:30:31 2020 -0600 > > io_uring: no read-retry on -EAGAIN error and O_NONBLOCK marked file > > Actually two things that need fixing up here: > > - The io_rw_reissue() -EAGAIN retry is explicit to block devices and > regular files, so don't ever attempt to do that on other types of > files. > > - If we hit -EAGAIN on a nonblock marked file, don't arm poll handler for > it. It should just complete with -EAGAIN. > > Cc: stable@vger.kernel.org > Reported-by: Norman Maurer > Signed-off-by: Jens Axboe > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index b1ccd7072d93..dc27cd5b8ad6 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -2300,8 +2300,11 @@ static bool io_resubmit_prep(struct io_kiocb *req, int error) > static bool io_rw_reissue(struct io_kiocb *req, long res) > { > #ifdef CONFIG_BLOCK > + umode_t mode = file_inode(req->file)->i_mode; > int ret; > > + if (!S_ISBLK(mode) && !S_ISREG(mode)) > + return false; > if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker()) > return false; > > @@ -3146,6 +3149,9 @@ static int io_read(struct io_kiocb *req, bool force_nonblock, > /* IOPOLL retry should happen for io-wq threads */ > if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL)) > goto done; > + /* no retry on NONBLOCK marked file */ > + if (kiocb->ki_flags & IOCB_NOWAIT) > + goto done; We clearing and setting IOCB_NOWAIT depending on @force_nonblock, so it may not work. E.g. with IOSQE_IO_ASYNC io_read() will clear it at the beginning. Maybe REQ_F_NOWAIT? > /* some cases will consume bytes even on error returns */ > iov_iter_revert(iter, iov_count - iov_iter_count(iter)); > ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false); > -- Pavel Begunkov