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Mon, 28 Oct 2019 04:12:33 -0700 (PDT) Received: from [192.168.43.153] ([109.126.132.16]) by smtp.gmail.com with ESMTPSA id i18sm11359931wrx.14.2019.10.28.04.12.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Oct 2019 04:12:33 -0700 (PDT) To: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <666ed447-ba8f-29e7-237f-de8044aa63ea@kernel.dk> <5ec9bd14-d8f2-32e6-7f25-0ca7256c408a@gmail.com> <57db9960-0b31-9f40-c13b-1db6dcc88920@gmail.com> <02a25d12-1f44-de18-f233-b5421c608469@kernel.dk> <63f93f8a-4207-3ac4-a301-4907882009c9@gmail.com> <728dec9c-465c-2341-d7b5-929a50400e9c@kernel.dk> <3b8b84d0-cde2-6bb0-c903-a1d71f9b83e2@gmail.com> <3957148b-0dac-a621-8f12-5d2d45557e24@kernel.dk> <1e0ae1a6-6b8b-a78e-8ec0-fb7aa5972d00@gmail.com> <02d42c75-1d48-35bd-abad-8230d2449c67@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: [PATCH 0/2][for-next] cleanup submission path Message-ID: <7cbec6a8-beb4-0738-9b4b-6d436efedc83@gmail.com> Date: Mon, 28 Oct 2019 14:12:19 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <02d42c75-1d48-35bd-abad-8230d2449c67@kernel.dk> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="i5bkzkjDhLVbrw7ROj8XCow8wOVHu95eE" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --i5bkzkjDhLVbrw7ROj8XCow8wOVHu95eE Content-Type: multipart/mixed; boundary="CqCjm4AXnxroyZqHLeEfYWAFw1eFjB4Vg"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <7cbec6a8-beb4-0738-9b4b-6d436efedc83@gmail.com> Subject: Re: [PATCH 0/2][for-next] cleanup submission path References: <666ed447-ba8f-29e7-237f-de8044aa63ea@kernel.dk> <5ec9bd14-d8f2-32e6-7f25-0ca7256c408a@gmail.com> <57db9960-0b31-9f40-c13b-1db6dcc88920@gmail.com> <02a25d12-1f44-de18-f233-b5421c608469@kernel.dk> <63f93f8a-4207-3ac4-a301-4907882009c9@gmail.com> <728dec9c-465c-2341-d7b5-929a50400e9c@kernel.dk> <3b8b84d0-cde2-6bb0-c903-a1d71f9b83e2@gmail.com> <3957148b-0dac-a621-8f12-5d2d45557e24@kernel.dk> <1e0ae1a6-6b8b-a78e-8ec0-fb7aa5972d00@gmail.com> <02d42c75-1d48-35bd-abad-8230d2449c67@kernel.dk> In-Reply-To: <02d42c75-1d48-35bd-abad-8230d2449c67@kernel.dk> --CqCjm4AXnxroyZqHLeEfYWAFw1eFjB4Vg Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 28/10/2019 06:38, Jens Axboe wrote: > On 10/27/19 1:59 PM, Pavel Begunkov wrote: >> On 27/10/2019 22:51, Jens Axboe wrote: >>> On 10/27/19 1:17 PM, Pavel Begunkov wrote: >>>> On 27/10/2019 22:02, Jens Axboe wrote: >>>>> On 10/27/19 12:56 PM, Pavel Begunkov wrote: >>>>>> On 27/10/2019 20:26, Jens Axboe wrote: >>>>>>> On 10/27/19 11:19 AM, Pavel Begunkov wrote: >>>>>>>> On 27/10/2019 19:56, Jens Axboe wrote: >>>>>>>>> On 10/27/19 10:49 AM, Jens Axboe wrote: >>>>>>>>>> On 10/27/19 10:44 AM, Pavel Begunkov wrote: >>>>>>>>>>> On 27/10/2019 19:32, Jens Axboe wrote: >>>>>>>>>>>> On 10/27/19 9:35 AM, Pavel Begunkov wrote: >>>>>>>>>>>>> A small cleanup of very similar but diverged io_submit_sqes= () and >>>>>>>>>>>>> io_ring_submit() >>>>>>>>>>>>> >>>>>>>>>>>>> Pavel Begunkov (2): >>>>>>>>>>>>> io_uring: handle mm_fault outside of submission >>>>>>>>>>>>> io_uring: merge io_submit_sqes and io_ring_submit >>>>>>>>>>>>> >>>>>>>>>>>>> fs/io_uring.c | 116 ++++++++++++++-----------------= ------------------- >>>>>>>>>>>>> 1 file changed, 33 insertions(+), 83 deletions(-) >>>>>>>>>>>> >>>>>>>>>>>> I like the cleanups here, but one thing that seems off is th= e >>>>>>>>>>>> assumption that io_sq_thread() always needs to grab the mm. = If >>>>>>>>>>>> the sqes processed are just READ/WRITE_FIXED, then it never = needs >>>>>>>>>>>> to grab the mm. >>>>>>>>>>>> Yeah, we removed it to fix bugs. Personally, I think it woul= d be >>>>>>>>>>> clearer to do lazy grabbing conditionally, rather than have t= wo >>>>>>>>>>> functions. And in this case it's easier to do after merging. >>>>>>>>>>> >>>>>>>>>>> Do you prefer to return it back first? >>>>>>>>>> >>>>>>>>>> Ah I see, no I don't care about that. >>>>>>>>> >>>>>>>>> OK, looked at the post-patches state. It's still not correct. Y= ou are >>>>>>>>> grabbing the mm from io_sq_thread() unconditionally. We should = not do >>>>>>>>> that, only if the sqes we need to submit need mm context. >>>>>>>>> >>>>>>>> That's what my question to the fix was about :) >>>>>>>> 1. Then, what the case it could fail? >>>>>>>> 2. Is it ok to hold it while polling? It could keep it for quite= >>>>>>>> a long time if host is swift, e.g. submit->poll->submit->poll-> = =2E.. >>>>>>>> >>>>>>>> Anyway, I will add it back and resend the patchset. >>>>>>> >>>>>>> If possible in a simple way, I'd prefer if we do it as a prep pat= ch and >>>>>>> then queue that up for 5.4 since we now lost that optimization. = Then >>>>>>> layer the other 2 on top of that, since I'll just rebase the 5.5 = stuff >>>>>>> on top of that. >>>>>>> >>>>>>> If not trivially possible for 5.4, then we'll just have to leave = with it >>>>>>> in that release. For that case, you can fold the change in with t= hese >>>>>>> two patches. >>>>>>> >>>>>> Hmm, what's the semantics? I think we should fail only those who n= eed >>>>>> mm, but can't get it. The alternative is to fail all subsequent af= ter >>>>>> the first mm_fault. >>>>> >>>>> For the sqthread setup, there's no notion of "do this many". It jus= t >>>>> grabs whatever it can and issues it. This means that the mm assign >>>>> is really per-sqe. What we did before, with the batching, just opti= mized >>>>> it so we'd only grab it for one batch IFF at least one sqe in that = batch >>>>> needed the mm. >>>>> >>>>> Since you've killed the batching, I think the logic should be somet= hing >>>>> ala: >>>>> >>>>> if (io_sqe_needs_user(sqe) && !cur_mm)) { >>>>> if (already_attempted_mmget_and_failed_ { >>>>> -EFAULT end sqe >>>>> } else { >>>>> do mm_get and mmuse dance >>>>> } >>>>> } >>>>> >>>>> Hence if the sqe doesn't need the mm, doesn't matter if we previous= ly >>>>> failed. If we need the mm and previously failed, -EFAULT. >>>>> >>>> That makes sense, but a bit hard to implement honoring links and dra= ins >>> >>> If it becomes too complicated or convoluted, just drop it. It's not >>> worth spending that much time on. >>> >> I've already done it more or less elegantly, just prefer to test commi= ts >> before sending. >=20 > That's always appreciated! >=20 > It struck me that while I've added quite a few regression tests, we don= 't > have any that just do basic read/write using the variety of settings we= > have for that. So I added that to liburing. >=20 Great, thanks! I think, I'll postpone patches including these until start of 5.5 --=20 Yours sincerely, Pavel Begunkov --CqCjm4AXnxroyZqHLeEfYWAFw1eFjB4Vg-- --i5bkzkjDhLVbrw7ROj8XCow8wOVHu95eE Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl22zRkACgkQWt5b1Glr +6U0fRAAj4teffPteuGV6bBcOazD+wOxdJrTAaDVaNz6yyE5Rqk+yxDHpQQQFQhm EcW48n35ApX3nim6OJ1Qk/Oe6QKYKqHrGNoR3hN6FXs1S6D9NpZtZepc2i4wNAQL tdcfKgnpXuZwPk8rZJL6r/gZ+WTy7qM2pCNz3kSWjKeWG0taVx42a3C/VN7sLLvA glQOrr85EebcVc5EEfvE4rIpZQTO8u9KibBb3THSrdmf5fFr65NbdquxVqsJcO9+ 7keg83+qnAeNQSL7ONpa/z6zkvBCwTFSxfPiqBUPl4OQr/CMb7LQEAPk5jv1nf8p Kr3qlUPXxFUb4iwCD/UA2tAnpN4YGLYmNX7qqYr58r8WJZSKtLgOUQsQcIA6/cHE ChceRv+WOMmpPZ6DOm9eA+3GuD6tJPEwuQix97t0/jjuGlhiMqyPADYkCyqUm+9H SaFHPMfXMlz704cMeJRJTne+4mYcJUQ/0/jP+EZajo1Wo6CtrDJzwI0XPvo5yOBd 3zRSm5Z8YKqz8exuNHdhcrodnSsvD8mnFomRpK3bPmZeuH4eSVmu9Xt2Jq81Yp1l pQ/FYKxBZMrLyK4Y5oQB5SOwkqMsZYkT9+KGOWojZvTAkFbq4h3HcsXD3sIiZEm2 AxvcxWjzGGbQZXI0ZB/Jx3OSBi8wi3RUwjKRyh5Xf0rVjaRWd1g= =aEDW -----END PGP SIGNATURE----- --i5bkzkjDhLVbrw7ROj8XCow8wOVHu95eE--